Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a column

[Scott McDonnell]

The M3x8mm truss head screws arrived today. They work great and would recommend 
them as a replacement if you can’t find the flanged screws.

I had not checked out ACE hardware. Lowes had a metric screw section the last 
time I was there. With the COVID crap, I have been doing mostly online shopping.

Still left to do in my M100 restoration project:

1. Replace the rubber feet on the bottoms of both
2. Retrobright the cases
3. Find some sort of replacement RAM modules
4. Find replacement power adapters

But for now, everything is working on both and it is time to start playing with 
and learning the M100.

Scott M.

From: B4 Me100
Sent: Sunday, December 20, 2020 11:18 PM
To: m...@bitchin100.com
Subject: Re: [M100] Model 100 Repair - Keyboard not responding,LCD missing a 
column

You might want to check you local ACE Hardware store I found they have Metric 
threaded machine screws that worked for me.  

Depending where you live of course :)

From: M100  on behalf of Scott McDonnell 

Reply-To: 
Date: Sunday, December 20, 2020 at 5:06 PM
To: "m...@bitchin100.com" 
Subject: Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a 
column

Regarding the screws… I think I found something that will work:
 
https://www.amazon.com/uxcell-Machine-Phillips-Stainless-Fasteners/dp/B07TDDY5M1/ref=sr_1_17?dchild=1=m3+phillips+truss=1608512236=p_85%3A2470955011=2470954011=1=8-17
 
M3x8mm Phillips Truss Head screws.
 
They are not the flanged button head screws like the original, but the only 
sources for those I have managed to find are in China (or ridiculously priced 
and still probably coming from China).
 
Regular pan heads will not work unless you use a washer. They may tighten down, 
but you risk cracking the case. You need the wider head. These are 7mm across. 
The original flanged heads are 7.5mm
 
These should work for the case and most of the screws on the inside as well. 
Just thought I would pass this along.
 
Scott M.

Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a column

[B4 Me100]

You might want to check you local ACE Hardware store I found they have
Metric threaded machine screws that worked for me.

Depending where you live of course :)

From:  M100  on behalf of Scott McDonnell

Reply-To:  
Date:  Sunday, December 20, 2020 at 5:06 PM
To:  "m...@bitchin100.com" 
Subject:  Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing
a column

> Regarding the screwsŠ I think I found something that will work:
>  
> https://www.amazon.com/uxcell-Machine-Phillips-Stainless-Fasteners/dp/B07TDDY5
> M1/ref=sr_1_17?dchild=1=m3+phillips+truss=1608512236=
> p_85%3A2470955011=2470954011=1=8-17
> <https://emea01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.amazon
> .com%2Fuxcell-Machine-Phillips-Stainless-Fasteners%2Fdp%2FB07TDDY5M1%2Fref%3Ds
> r_1_17%3Fdchild%3D1%26keywords%3Dm3%2Bphillips%2Btruss%26qid%3D1608512236%26re
> finements%3Dp_85%253A2470955011%26rnid%3D2470954011%26rps%3D1%26sr%3D8-17
> =04%7C01%7C%7C358502a43b2743e3051e08d8a54ca955%7C84df9e7fe9f640afb435a
> aaa%7C1%7C0%7C637441095967750461%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiL
> CJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000=pXHHVFzCiwiogbg9OTZ
> elEjrhXV1l4i%2BE7wY%2FiI2C%2BY%3D=0>
>  
> M3x8mm Phillips Truss Head screws.
>  
> They are not the flanged button head screws like the original, but the only
> sources for those I have managed to find are in China (or ridiculously priced
> and still probably coming from China).
>  
> Regular pan heads will not work unless you use a washer. They may tighten
> down, but you risk cracking the case. You need the wider head. These are 7mm
> across. The original flanged heads are 7.5mm
>  
> These should work for the case and most of the screws on the inside as well.
> Just thought I would pass this along.
>  
> Scott M.

Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a column

[Scott McDonnell]

Regarding the screws… I think I found something that will work:

https://www.amazon.com/uxcell-Machine-Phillips-Stainless-Fasteners/dp/B07TDDY5M1/ref=sr_1_17?dchild=1=m3+phillips+truss=1608512236=p_85%3A2470955011=2470954011=1=8-17

M3x8mm Phillips Truss Head screws.

They are not the flanged button head screws like the original, but the only 
sources for those I have managed to find are in China (or ridiculously priced 
and still probably coming from China).

Regular pan heads will not work unless you use a washer. They may tighten down, 
but you risk cracking the case. You need the wider head. These are 7mm across. 
The original flanged heads are 7.5mm

These should work for the case and most of the screws on the inside as well. 
Just thought I would pass this along.

Scott M.


From: Scott McDonnell
Sent: Saturday, December 19, 2020 1:47 PM
To: m...@bitchin100.com
Subject: Re: [M100] Model 100 Repair - Keyboard not responding,LCD missing a 
column

Doubtful. Remember this was made in Japan by Kyocera originally. So most likely 
metric screws.

Ahh yes, service manual calls out M3x8 machine screws! I have those!

Scott

From: Michael Kohne
Sent: Saturday, December 19, 2020 1:39 PM
To: m...@bitchin100.com
Subject: Re: [M100] Model 100 Repair - Keyboard not responding,LCD missing a 
column

I believe that the screws on the back are #4-48, which is not the most common 
thing in the world (most #4 screws are 40 TPI). 
If anyone knows where to get a Phillips head screw in that size, I'd be 
grateful, as so far I've only found socket-head screws.

On Sat, Dec 19, 2020 at 12:52 PM Scott McDonnell  
wrote:
Tada!!
 
Well, it turned out that 5 traces were broken. The 4 I didn’t see were broken 
right at the ring, so 3 of them were easy to fix with just scratching back the 
trace a bit and solder bridging. I did need to add one more jumper wire. So two 
wire jumpers and the rest looks mostly normal.
 
Obviously, I installed a socket in the main RAM slot.
 
And well, now this non-working M100 is working!
 
I looked over the caps and the NiCad battery. They are all aftermarket, so 
previous owner did all this updating (probably thinking that was why it wasn’t 
working.)
 
I also took the opportunity to burn a Y2K patched ROM that I did on a 27C256.
 
Still left to do:
 
Sort out the LCD. I think I just need to add some pressure to the LCD.
Run a diagnostic program to determine which one of the RAM modules is bad. It 
reports the 29+K bytes free with all modules in there, but obviously the 
original RAM module at least is bad. Maybe I will buy aftermarket modules if 
someone would be kind enough to point me to a place to buy.
 
I need to replace some screws. It had none of the back cover screws. Hopefully 
the service manual will tell me the screw size I need.
Cast and mold (or find someone selling one) a new battery door. This one was 
missing the battery door. (Anyone have a spare they would be willing to part 
with?)
 
I was using the “good M100” screen and keyboard for troubleshooting:
 

 
From: Josh Malone
Sent: Thursday, December 17, 2020 2:48 PM
To: m...@bitchin100.com
Subject: Re: [M100] Model 100 Repair - Keyboard not responding,LCD missing a 
column
 
On Thu, Dec 17, 2020 at 2:08 PM mcdonnell.junk
 wrote:
> 
> And, well, I *did* break a trace and possibly pulled out a barrel. Lol. That 
> was likely my impatience and not the tool. I did test the force requir3d to 
> pop the chip out before prying on it and it came out easy, so I thought all 
> was good.
 
Yeah - impatience got me when I was working in my ZX Spectrum +2 a
couple months ago. Lifted 2 pads when removing a PLA because I was
hungry and wanted to finish the job before dinner. D'oh!
 
-Josh
 


-- 
Michael Kohne
mhko...@kohne.org

Anything real you do that's important will be scary. Having kids. Getting 
married. Donating a kidney.  Writing a book. Do it anyway. - Neil Gaiman

Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a column

[Brian K. White]

DTR is also used to tell TS-DOS when it's ok to talk, but you can get 
away without it by just shorting it in the connector. Well, in the case 
of using the serial port. Not sure what you'd do inside the M100 that 
would allow you to assert it when you're using the uart and not when you 
go hands-off to let the serial port have it.


Basically, TS-DOS looks at it, and it's better, safer for your ram 
contents, if it's being set correctly so that the TS-DOS does not try to 
read or write when the tpdd is not going to actually respond properly.


But it's not super harmful, it usually just hangs ts-dos, and usually 
you can break out without a hard reset or a crash where you lose ram. 
And that's just if you go in to ts-dos and try to make it read the 
directory or read or write a file while there is no actual tpdd 
responding. It's pretty easy to just "don't do that".


But with the lines hooked up and the firmware asserting them right, it's 
a safer more user-friendly experience with fewer unpleasant surprises.


It's not used for normal flow control, just graceful "drive-not-ready".

In the other direction, asserting to the tpdd, it's only used to detect 
the bootstrap conditions. Actually I don't remember, once I had the pins 
wired up and working maybe I did also add graceful "host-not-ready" just 
for the heck of it, but it wouldn't actually matter. Even if it's in 
there, you can ignore it. The drive never initiates anything so there is 
really almost no need for the drive to check if the host is ready. The 
drive just spins waiting for commands and reacts to them. If you get a 
command, you are pretty much always ok to go ahead and perform that 
command. If someone yanks a cable out in the middle of some action, they 
already expect that transaction to be junk.


Put it this way, for quite a while the first versions didn't even have 
any dsr or dtr at all. Just shorted in the connector to pacify ts-dos 
and nothing on the arduino side at all.


But a real tpdd has it, and TS-DOS (and I think the official FLOPPY that 
came with the drive) use it.


--
bkw


On 12/19/20 10:31 PM, Scott McDonnell wrote:
I’ve used these before in other projects and they worked great. One use 
was to replace a serial printer on one of our very old test stations at 
work. I was going to make my own boards to do it and then stumbled on 
this. Cheaper than the parts I would have had to buy. That’s why when I 
seen PDDuino, I thought about these.


My plan is to install inside the M100, however I won’t totally get away 
without additional hardware. I would probably add a buffer so that the 
serial port can still be used. I would need a level shifter (from 5V and 
3.3V) anyway, which is basically a buffer. That should also protect the 
M100 from any nonsense the Arduino might cause.


I had not considered the DTR signal, but you do actually have more I/O. 
You could use the MOSI or MISO pins at startup. It would do nothing to 
the SD card because it wouldn’t be chip-selected yet. Or, it is a bit of 
a hack, but you could tap into one of the two LEDs since it would be 
inside the M100 and you wouldn’t see the LEDs anyway. And of course, you 
could break one of the two ground pins and jumper to any other IO pin on 
the ATMega chip and bring it to that pin.


I haven’t studied the code in detail yet, but do you need the DTS/DTR 
signal for the initial bootstrap process only?


Scott M.

*From: *Brian K. White <mailto:b.kenyo...@gmail.com>
*Sent: *Saturday, December 19, 2020 10:12 PM
*To: *m...@bitchin100.com <mailto:m...@bitchin100.com>
*Subject: *Re: [M100] Model 100 Repair - Keyboard not responding,LCD 
missing a column


I started to try that too a while back, but I think I might have gotten

some bad units. I only barely got them to work even just with basic

hello-world code or using the pre-installed serial-logging firmware.

Maybe I killed the i/o with 5v?

One problem with these is you still need to add a rs232 level-shifter,

unless you're talking about wiring up directly to the uart, but then

it's a very different kind of project, not a plug & play

damage-free-towing kind of thing any more. Then again, arduino dev

boards need that too, which is what MounT is.

Then there is the bootstrap, you'd need to come up with some other way

to trigger the bootstrap, or just not have that. There's no other io

lines available to use as dsr/dtr.

Probably the simplest is just have the tpdd server code recognize a

special command that could be sent more or less any time, with no

special power up sequence of events and setting up of conditions. The

downside is it makes the BASIC code you have to manually enter a bit longer.

dlplus originally had something like that, except do something a bit

better than exactly what dlplus did, like instead of "XX means do

bootstrap" more like "XX means alternate commands prefix" and the

command to invoke bootstrap would 

Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a column

[RETRO Innovations]

On 12/19/2020 8:26 PM, Brian K. White wrote:

On 12/19/20 8:32 PM, Scott McDonnell wrote:

Ha. Wait… this is Brian White’s program, too, isn’t it? 


It's really Jimmy Petit's, which I then hacked on.
Jim Brain has taken mine and hacked some more too, though that's in 
rough shape too as it was a more major refactor and it both cleans up 
some things and introduces new breakage. I have been meaning to adopt 
the first few of his patches which do fix up several things. We were 
working on it together back & forth for about one solid weekend a few 
months ago and were starting to get somewhere.



Yep, my apologies.  I have done the following:

 * I replaced the complex ring buffer construct in the codebase with a
   simpler buffer
 * I refactored all of the source into a few different files, to make
   the code a bit easier to read
 * Migrated all "magic values" into defines
 * Moved all defines and such to header files
 * Moved to a little easier logging system
 * Refactored a bunch of the global variables into local when global
   was not needed
 * Added in some of the extensions found in other solutions

All that should be relatively solid, and I can create a release of those 
items.


I also am in the process of virtualizing the filesystem, since I think 
the SDFatFS lib is a bit big for this use case and FatFS might be more 
space efficient.  I have the SDFat lib virtualized, but ran into a 
problem adding in FatFS, and then I got called onto a project in my day 
job and need to get back to it.


I will commit to working on it over the Holidays if there's some 
interest in testing.


I'd like to get the codebase to dual compile using Arduino IDE and a 
standard Makefile, since I know compiling as a normal C project saves a 
couple kB of flash on many platforms, and that could be helpful.  It 
will also allow me to compile the same code as a cygwin/linux app, to 
save some development cycles.


Jim

--
RETRO Innovations, Contemporary Gear for Classic Systems
www.go4retro.com
store.go4retro.com

Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a column

[John R. Hogerhuis]

On Sat, Dec 19, 2020 at 7:12 PM Brian K. White  wrote:

>
> Then there is the bootstrap, you'd need to come up with some other way
> to trigger the bootstrap, or just not have that. There's no other io
> lines available to use as dsr/dtr.
>
>
My policy on bootstrap for LaddieAlpha was... buy a REX. Since there's
always a way. Just use a TELCOM  or TEXT/F2 and a PC terminal program to
inject a .DO formatted TEENY.

Actually, DLPilot which came before my variant of DLPlus and LaddieAlpha
had a generic text file injector. But that was special because it ran on a
Palm Pilot, so I was able to select the text file, and the user could
trigger transfer from the UI when they were ready.

Another way you could go is the NADSBox way... a general purpose CLI. As
in, you open TELCOM at 19200, you hit ENTER a couple of times at human
speeds and the TPDD server state machine puts you into "interactive mode"
and you get a prompt. It stays in that mode until a ZZ command comes. So
you could do the NADSBox style copy command. Maybe with a time-delay.

I have a start on something like that for LaddieAlpha but it's more of 2D
shell. As in, it presents you a full screen curses type UI from within
Telcom, showing the files on the host PC current directory. Then you move
the widebar cursor over to a file and you can transmit it. Throwing the
file is easy. The tricky bit is catching it.

I am thinking the way to do that is after the Transmit operation is
invoked, you give the user instructions to exit Telcom, enter TEXT and Hit
F2, COM:98N1E, etc.

The host side watches for DSR going deasserted (because TELCOM is exited),
and then asserted again once the user follows the TEXT/F2 steps. So DSR
going asserted again is the trigger for sending the Ctrl-Z terminated text
file.

That's for injecting a file. Alternatively to using TEXT/F2, the user could
enter BASIC and RUN"COM:98N1E to do an active bootstrap.

-- John.

Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a column

[Scott McDonnell]

I’ve used these before in other projects and they worked great. One use was to 
replace a serial printer on one of our very old test stations at work. I was 
going to make my own boards to do it and then stumbled on this. Cheaper than 
the parts I would have had to buy. That’s why when I seen PDDuino, I thought 
about these. 

My plan is to install inside the M100, however I won’t totally get away without 
additional hardware. I would probably add a buffer so that the serial port can 
still be used. I would need a level shifter (from 5V and 3.3V) anyway, which is 
basically a buffer. That should also protect the M100 from any nonsense the 
Arduino might cause.

I had not considered the DTR signal, but you do actually have more I/O. You 
could use the MOSI or MISO pins at startup. It would do nothing to the SD card 
because it wouldn’t be chip-selected yet. Or, it is a bit of a hack, but you 
could tap into one of the two LEDs since it would be inside the M100 and you 
wouldn’t see the LEDs anyway. And of course, you could break one of the two 
ground pins and jumper to any other IO pin on the ATMega chip and bring it to 
that pin. 

I haven’t studied the code in detail yet, but do you need the DTS/DTR signal 
for the initial bootstrap process only?

Scott M.

From: Brian K. White
Sent: Saturday, December 19, 2020 10:12 PM
To: m...@bitchin100.com
Subject: Re: [M100] Model 100 Repair - Keyboard not responding,LCD missing a 
column

I started to try that too a while back, but I think I might have gotten 
some bad units. I only barely got them to work even just with basic 
hello-world code or using the pre-installed serial-logging firmware. 
Maybe I killed the i/o with 5v?

One problem with these is you still need to add a rs232 level-shifter, 
unless you're talking about wiring up directly to the uart, but then 
it's a very different kind of project, not a plug & play 
damage-free-towing kind of thing any more. Then again, arduino dev 
boards need that too, which is what MounT is.

Then there is the bootstrap, you'd need to come up with some other way 
to trigger the bootstrap, or just not have that. There's no other io 
lines available to use as dsr/dtr.

Probably the simplest is just have the tpdd server code recognize a 
special command that could be sent more or less any time, with no 
special power up sequence of events and setting up of conditions. The 
downside is it makes the BASIC code you have to manually enter a bit longer.

dlplus originally had something like that, except do something a bit 
better than exactly what dlplus did, like instead of "XX means do 
bootstrap" more like "XX means alternate commands prefix" and the 
command to invoke bootstrap would be XX-something- just like how all 
TPDD commands are ZZ-something-

(I think the original subdirectory extensions made by TS-DOS should have 
been done that way too instead of using ZZ-previously-unused-number. 
ZZ-everything- should have been considered off limits and owned by 
someone else.)

I think mComm has something like the original dlplus mechanism too.

I do think the microcontroller is up to the task. It's normal 
off-the-shelf job is already to do exactly the same work, 
rs232<->sdcard. TPDD is nothing else unless you count the packet checksums.

-- 
bkw

> https://www.amazon.com/gp/product/B07T6HBMTZ/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8=1
>  
> <https://www.amazon.com/gp/product/B07T6HBMTZ/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8=1>
> 
> Looks fairly straight-forward so far.
> 
> Looks small enough that one could mount right inside the M100 in the 
> option ROM area. There is also a bit of room just above the barcode 
> reader port. It may fit there, exposing the microSD card.



-- 
bkw

Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a column

[Brian K. White]

I started to try that too a while back, but I think I might have gotten 
some bad units. I only barely got them to work even just with basic 
hello-world code or using the pre-installed serial-logging firmware. 
Maybe I killed the i/o with 5v?


One problem with these is you still need to add a rs232 level-shifter, 
unless you're talking about wiring up directly to the uart, but then 
it's a very different kind of project, not a plug & play 
damage-free-towing kind of thing any more. Then again, arduino dev 
boards need that too, which is what MounT is.


Then there is the bootstrap, you'd need to come up with some other way 
to trigger the bootstrap, or just not have that. There's no other io 
lines available to use as dsr/dtr.


Probably the simplest is just have the tpdd server code recognize a 
special command that could be sent more or less any time, with no 
special power up sequence of events and setting up of conditions. The 
downside is it makes the BASIC code you have to manually enter a bit longer.


dlplus originally had something like that, except do something a bit 
better than exactly what dlplus did, like instead of "XX means do 
bootstrap" more like "XX means alternate commands prefix" and the 
command to invoke bootstrap would be XX-something- just like how all 
TPDD commands are ZZ-something-


(I think the original subdirectory extensions made by TS-DOS should have 
been done that way too instead of using ZZ-previously-unused-number. 
ZZ-everything- should have been considered off limits and owned by 
someone else.)


I think mComm has something like the original dlplus mechanism too.

I do think the microcontroller is up to the task. It's normal 
off-the-shelf job is already to do exactly the same work, 
rs232<->sdcard. TPDD is nothing else unless you count the packet checksums.


--
bkw

https://www.amazon.com/gp/product/B07T6HBMTZ/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8=1 



Looks fairly straight-forward so far.

Looks small enough that one could mount right inside the M100 in the 
option ROM area. There is also a bit of room just above the barcode 
reader port. It may fit there, exposing the microSD card.




--
bkw

Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a column

[Scott McDonnell]

“Anything worth having is worth working for.”

Scott M.

From: Brian K. White
Sent: Saturday, December 19, 2020 9:18 PM
To: m...@bitchin100.com
Subject: Re: [M100] Model 100 Repair - Keyboard not responding,LCD missing a 
column

Be advised, the software needs work. It's more than proof of concept 
since it actually works fine outwardly IF you just use TS-DOS as the 
client DOS on the 100. But it's still swiss cheese and doesn't work with 
all kinds of other things that it *should* work with.

I think it's not far off and the remaining cleanup is actually pretty 
small. But just so you don't think it's more than it is. I hope I was 
clear enough about that both in the video and the readme.

-- 
bkw

Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a column

[Brian K. White]

On 12/19/20 8:32 PM, Scott McDonnell wrote:

Ha. Wait… this is Brian White’s program, too, isn’t it? 


It's really Jimmy Petit's, which I then hacked on.
Jim Brain has taken mine and hacked some more too, though that's in 
rough shape too as it was a more major refactor and it both cleans up 
some things and introduces new breakage. I have been meaning to adopt 
the first few of his patches which do fix up several things. We were 
working on it together back & forth for about one solid weekend a few 
months ago and were starting to get somewhere.


--
bkw

Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a column

[Brian K. White]

Be advised, the software needs work. It's more than proof of concept 
since it actually works fine outwardly IF you just use TS-DOS as the 
client DOS on the 100. But it's still swiss cheese and doesn't work with 
all kinds of other things that it *should* work with.


I think it's not far off and the remaining cleanup is actually pretty 
small. But just so you don't think it's more than it is. I hope I was 
clear enough about that both in the video and the readme.


--
bkw


On 12/19/20 8:28 PM, Scott McDonnell wrote:
Once I get ducks in a row, I am planning to look into porting PDDuino 
(hardware TPDD emulator) https://github.com/bkw777/PDDuino 
<https://github.com/bkw777/PDDuino> over to this:


https://www.amazon.com/gp/product/B07T6HBMTZ/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8=1 
<https://www.amazon.com/gp/product/B07T6HBMTZ/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8=1>


Looks fairly straight-forward so far.

Looks small enough that one could mount right inside the M100 in the 
option ROM area. There is also a bit of room just above the barcode 
reader port. It may fit there, exposing the microSD card.


I’ll keep you all updated on progress. I will be working on it over xmas 
break.


Scott M.

*From: *Joshua O'Keefe <mailto:maj...@nachomountain.com>
*Sent: *Saturday, December 19, 2020 7:35 PM
*To: *m...@bitchin100.com <mailto:m...@bitchin100.com>
*Subject: *Re: [M100] Model 100 Repair - Keyboard not responding,LCD 
missing a column


On Dec 19, 2020, at 3:35 PM, Scott McDonnell <mailto:mcdonnell.j...@comcast.net>> wrote:


What I would like to be able to do:

Replace the main ROM

REX Classic supports this, but the more current versions of REX do not.



Custom menu

Whatever main ROM replacement solution you choose would be how you 
approach this aspect of the project.  I’m not doing ROM hacking so I 
don’t have much to add here.




My apps not stored in RAM dependent on battery

REX is great for this.  it allows you to dump the contents of main RAM 
to flash and restore from it arbitrarily.  It also has a facility for 
retrieving individual files from within various RAM backups.  Note that 
REXCPM is a battery backed device while the others are flash based.  My 
102 is a daily driver for me as much as a retrocomputing toy, and my REX 
is a major component of making the system useful for a broad variety of 
tasks on a daily basis.




Autolauch a program at power on (and preferably be able to exit out
to menu if wanted)

I am very interested in the solution you come up with for this.  The IPL 
command doesn’t provide the facility to use the menu at will since any 
access of the menu will immediately trigger the IPL program.  In fact 
it’s pretty easy to lock yourself out of the menu with careless use of 
the IPL command.  Ask me how I know!




Ease transfer of files back and forth with a PC (TPDD emulator or
Trashtalk)

The common case for many users here is a REX (of whichever kind) with 
TS-DOS as one of the option ROMs, paired with a TPDD emulator like 
mComm, mComm Python, LaddieAlpha, or dlplus on the host end.  Of these, 
LaddieAlpha is perhaps the most featureful while mComm is a common 
choice for Android hosts that are often used for portable battery-backed 
TPDD emulation.  mComm Python and dlplus are pretty portable to various 
platforms and have fairly compact codebases.  LaddieAlpha runs pretty 
much anywhere Mono does in my experience.  There are a number of TS-DOS 
option ROM images floating about from which to choose.  I prefer Kurt’s 
“4.10” version as it’s the version closest to the vanilla ROM but it has 
an annoying UI bug fixed.  It’s also the TS-DOS version used in the 
SARDOS option ROM.


I do a fair amount of writing in both plain text and LaTeX on the 102, 
and transfer to larger machines for storage and typesetting is a big 
part of my workflow so this subject is near and dear to my heart.





--
bkw

Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a column

[Scott McDonnell]

Ha. Wait… this is Brian White’s program, too, isn’t it? 

Scott M.

From: Scott McDonnell
Sent: Saturday, December 19, 2020 8:29 PM
To: m...@bitchin100.com
Subject: Re: [M100] Model 100 Repair - Keyboard not responding,LCD missing a 
column

Once I get ducks in a row, I am planning to look into porting PDDuino (hardware 
TPDD emulator) https://github.com/bkw777/PDDuino over to this:

https://www.amazon.com/gp/product/B07T6HBMTZ/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8=1

Looks fairly straight-forward so far.

Looks small enough that one could mount right inside the M100 in the option ROM 
area. There is also a bit of room just above the barcode reader port. It may 
fit there, exposing the microSD card.

I’ll keep you all updated on progress. I will be working on it over xmas break.

Scott M.

From: Joshua O'Keefe
Sent: Saturday, December 19, 2020 7:35 PM
To: m...@bitchin100.com
Subject: Re: [M100] Model 100 Repair - Keyboard not responding,LCD missing a 
column

On Dec 19, 2020, at 3:35 PM, Scott McDonnell  wrote:
What I would like to be able to do:
Replace the main ROM

REX Classic supports this, but the more current versions of REX do not.

Custom menu

Whatever main ROM replacement solution you choose would be how you approach 
this aspect of the project.  I’m not doing ROM hacking so I don’t have much to 
add here.

My apps not stored in RAM dependent on battery

REX is great for this.  it allows you to dump the contents of main RAM to flash 
and restore from it arbitrarily.  It also has a facility for retrieving 
individual files from within various RAM backups.  Note that REXCPM is a 
battery backed device while the others are flash based.  My 102 is a daily 
driver for me as much as a retrocomputing toy, and my REX is a major component 
of making the system useful for a broad variety of tasks on a daily basis.

Autolauch a program at power on (and preferably be able to exit out to menu if 
wanted)

I am very interested in the solution you come up with for this.  The IPL 
command doesn’t provide the facility to use the menu at will since any access 
of the menu will immediately trigger the IPL program.  In fact it’s pretty easy 
to lock yourself out of the menu with careless use of the IPL command.  Ask me 
how I know!

Ease transfer of files back and forth with a PC (TPDD emulator or Trashtalk)

The common case for many users here is a REX (of whichever kind) with TS-DOS as 
one of the option ROMs, paired with a TPDD emulator like mComm, mComm Python, 
LaddieAlpha, or dlplus on the host end.  Of these, LaddieAlpha is perhaps the 
most featureful while mComm is a common choice for Android hosts that are often 
used for portable battery-backed TPDD emulation.  mComm Python and dlplus are 
pretty portable to various platforms and have fairly compact codebases.  
LaddieAlpha runs pretty much anywhere Mono does in my experience.  There are a 
number of TS-DOS option ROM images floating about from which to choose.  I 
prefer Kurt’s “4.10” version as it’s the version closest to the vanilla ROM but 
it has an annoying UI bug fixed.  It’s also the TS-DOS version used in the 
SARDOS option ROM.

I do a fair amount of writing in both plain text and LaTeX on the 102, and 
transfer to larger machines for storage and typesetting is a big part of my 
workflow so this subject is near and dear to my heart.

Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a column

[Scott McDonnell]

Once I get ducks in a row, I am planning to look into porting PDDuino (hardware 
TPDD emulator) https://github.com/bkw777/PDDuino over to this:

https://www.amazon.com/gp/product/B07T6HBMTZ/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8=1

Looks fairly straight-forward so far.

Looks small enough that one could mount right inside the M100 in the option ROM 
area. There is also a bit of room just above the barcode reader port. It may 
fit there, exposing the microSD card.

I’ll keep you all updated on progress. I will be working on it over xmas break.

Scott M.

From: Joshua O'Keefe
Sent: Saturday, December 19, 2020 7:35 PM
To: m...@bitchin100.com
Subject: Re: [M100] Model 100 Repair - Keyboard not responding,LCD missing a 
column

On Dec 19, 2020, at 3:35 PM, Scott McDonnell  wrote:
What I would like to be able to do:
Replace the main ROM

REX Classic supports this, but the more current versions of REX do not.


Custom menu

Whatever main ROM replacement solution you choose would be how you approach 
this aspect of the project.  I’m not doing ROM hacking so I don’t have much to 
add here.


My apps not stored in RAM dependent on battery

REX is great for this.  it allows you to dump the contents of main RAM to flash 
and restore from it arbitrarily.  It also has a facility for retrieving 
individual files from within various RAM backups.  Note that REXCPM is a 
battery backed device while the others are flash based.  My 102 is a daily 
driver for me as much as a retrocomputing toy, and my REX is a major component 
of making the system useful for a broad variety of tasks on a daily basis.


Autolauch a program at power on (and preferably be able to exit out to menu if 
wanted)

I am very interested in the solution you come up with for this.  The IPL 
command doesn’t provide the facility to use the menu at will since any access 
of the menu will immediately trigger the IPL program.  In fact it’s pretty easy 
to lock yourself out of the menu with careless use of the IPL command.  Ask me 
how I know!


Ease transfer of files back and forth with a PC (TPDD emulator or Trashtalk)

The common case for many users here is a REX (of whichever kind) with TS-DOS as 
one of the option ROMs, paired with a TPDD emulator like mComm, mComm Python, 
LaddieAlpha, or dlplus on the host end.  Of these, LaddieAlpha is perhaps the 
most featureful while mComm is a common choice for Android hosts that are often 
used for portable battery-backed TPDD emulation.  mComm Python and dlplus are 
pretty portable to various platforms and have fairly compact codebases.  
LaddieAlpha runs pretty much anywhere Mono does in my experience.  There are a 
number of TS-DOS option ROM images floating about from which to choose.  I 
prefer Kurt’s “4.10” version as it’s the version closest to the vanilla ROM but 
it has an annoying UI bug fixed.  It’s also the TS-DOS version used in the 
SARDOS option ROM.

I do a fair amount of writing in both plain text and LaTeX on the 102, and 
transfer to larger machines for storage and typesetting is a big part of my 
workflow so this subject is near and dear to my heart.

Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a column

[John R. Hogerhuis]

I see no problem with this.

Rex is a hardware+software combo for sale. All software has bugs. He
supported it for a long time, even allowing third party hardware to use his
(binary) software, firmware. I think users expect that at some point you
stop getting feature updates and bugfixes and if you want new fixes and
features you buy the new stuff.

And even if there are some known issues with the original Rex, it works
well nevertheless.

-- John.

>

Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a column

[Brian White]

Rex classic *can* replace the main rom. It doesn't normally but it has the
option if you set it up.

It installs into the option rom socket and it's main job is actually to be
an on-board option rom library, where you can load up option rom images and
switch between them all purely from software. It can also take full ram
image backups and restore them, and finally it has two special blocks of
memory for main rom images. In order for the rex to take over the job of
the main rom, it needs the rom image loaded into it, and the /CS signal
line for the main rom run out to a pin on the rex so that when the
motherboard calls for the main rom to be active, the rex can respond
instead.

Just read the docs on bitchin100 and tandy.wiki about it.

REX# and REXCPM don't offer the feature so there is no other really
convenient way to hack on the main rom. You have to open the case
repeatedly to actually remove the rom, or run some kind of janky ribbon
cable to an external socket.

Unless you count VirtualT, but then you are debugging getting a rom to work
with an emulator not with the hardware.

I have to say, if I had paid Steve for a classic rex as many people have by
now, I would be pretty upset at hearing "It has bugs I know about but I'm
not going to fix."

My 2 cents as a user.

Steve, would you consider describing the bugs and making the sources
available for the several binary blobs that rex classic currently relies
on, so that someone else can fix what you don't want to?

For one thing, a totally different issue, I have wished I could fix the
tpdd routine in the installer that seems to have changed in some way after
build 162. It's inarguably broken, proven by the simple experiment that it
doesn't work with a real tpdd.

Right now the situation is, you won't fix something, and you won't let
anyone else fix it either. Can you possibly see how that might be just a
bit frustrating for a user?

-- 
bkw


On Sat, Dec 19, 2020, 6:35 PM Scott McDonnell 
wrote:

> Will do. Just so I understand, the Rex replaces the main rom? The M100
> will boot directly from the Rex? And with the Rex, I can customize my own
> applications, autolaunch, etc? This goes into the DVI socket on the bottom?
>
>
>
> I had looked at it before, but the descriptions seem to be written for
> people that are already well into the Model 100 and not very clear to a
> TRS-80 newbie like me. :)
>
>
>
> What I would like to be able to do:
>
> Replace the main ROM
>
> Custom menu
>
> My apps not stored in RAM dependent on battery
>
> Autolauch a program at power on (and preferably be able to exit out to
> menu if wanted)
>
> Ease transfer of files back and forth with a PC (TPDD emulator or
> Trashtalk)
>
>
>
> Thank you to everyone that has replied.
>
>
>
> *From: *Stephen Adolph 
> *Sent: *Saturday, December 19, 2020 6:27 PM
> *To: *m...@bitchin100.com
> *Subject: *Re: [M100] Model 100 Repair - Keyboard not responding,LCD
> missing a column
>
>
>
> Scott, I recommend before you jump into a REX solution that you read my
> REX# and REXCPM wiki pages at Bitchin100.
>
> REX Classic is the DIY option, but I no longer support it, and it has
> known defects.
>
> My 2 cents as the designer... Steve
>
>
>
>
>
>
>
> On Sat, Dec 19, 2020 at 6:12 PM Brian White  wrote:
>
> Actually with rex classic you don't even need any rom in the main rom
> socket so you don't need any of those boards, just a single wire from the
> /CS pin in the main rom socket out to the REX. You just can't run the
> machine *without* the rex after that without opening back up to put a rom
> back. The flexrom board just lets you install or remove the rex at will, as
> well as being re-writable itself by being a 28C256.
>
>
>
> On Sat, Dec 19, 2020, 6:04 PM Brian White  wrote:
>
>
>
> On Sat, Dec 19, 2020, 2:38 PM Scott McDonnell 
> wrote:
>
> Now that I have proven out that a 27C256 EPROM is working fine in this
> one, I am going to play around with customizing it. The real ULTIMATE would
> be to replace the ROM with an EEPROM (like 28C256) and add in some type of
> loader where you could update the main firmware over serial. That may not
> be possible because often in these 80’s computers they usually placed some
> IO address space in the ROM area (since write is not possible to the ROM)
> and decoded it using the write signal and address. It was a simple trick
> for accessing output only IO. I am talking out of my rear end right now
> because I haven’t studied the schematic/memory map in detail yet.
>
>
>
> http://tandy.wiki/FlexROM_100
>
>
>
> http://tandy.wiki/FlexROM_102
>
>
>
> Especially in concert with REX Classic
>
>
>
> http://tandy.wiki/Building_a_REX
>
> or
>
> arcad

Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a column

[Joshua O'Keefe]

On Dec 19, 2020, at 3:35 PM, Scott McDonnell  wrote:
> What I would like to be able to do:
> Replace the main ROM

REX Classic supports this, but the more current versions of REX do not.

> Custom menu

Whatever main ROM replacement solution you choose would be how you approach 
this aspect of the project.  I’m not doing ROM hacking so I don’t have much to 
add here.

> My apps not stored in RAM dependent on battery

REX is great for this.  it allows you to dump the contents of main RAM to flash 
and restore from it arbitrarily.  It also has a facility for retrieving 
individual files from within various RAM backups.  Note that REXCPM is a 
battery backed device while the others are flash based.  My 102 is a daily 
driver for me as much as a retrocomputing toy, and my REX is a major component 
of making the system useful for a broad variety of tasks on a daily basis.

> Autolauch a program at power on (and preferably be able to exit out to menu 
> if wanted)

I am very interested in the solution you come up with for this.  The IPL 
command doesn’t provide the facility to use the menu at will since any access 
of the menu will immediately trigger the IPL program.  In fact it’s pretty easy 
to lock yourself out of the menu with careless use of the IPL command.  Ask me 
how I know!

> Ease transfer of files back and forth with a PC (TPDD emulator or Trashtalk)

The common case for many users here is a REX (of whichever kind) with TS-DOS as 
one of the option ROMs, paired with a TPDD emulator like mComm, mComm Python, 
LaddieAlpha, or dlplus on the host end.  Of these, LaddieAlpha is perhaps the 
most featureful while mComm is a common choice for Android hosts that are often 
used for portable battery-backed TPDD emulation.  mComm Python and dlplus are 
pretty portable to various platforms and have fairly compact codebases.  
LaddieAlpha runs pretty much anywhere Mono does in my experience.  There are a 
number of TS-DOS option ROM images floating about from which to choose.  I 
prefer Kurt’s “4.10” version as it’s the version closest to the vanilla ROM but 
it has an annoying UI bug fixed.  It’s also the TS-DOS version used in the 
SARDOS option ROM.

I do a fair amount of writing in both plain text and LaTeX on the 102, and 
transfer to larger machines for storage and typesetting is a big part of my 
workflow so this subject is near and dear to my heart.

Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a column

[Stephen Adolph]

Just email me directly.  Building over the holiday weeks.  I have quite a
backlig to clear but I am trying to release a big update in the next day or
so.  Lots of testing..

Fyi everyone.
Next drop of REX# re-implelemts multi bank for T200 and NEC, as well as the
integrated VT100 driver for M100 only. Also, new quick menu keystroke...
CNTL-A to start REXMGR.  Also, a major bug is addressed.

I will have to update the wiki page on VT100, ro describe the extended
BASIC commands.

I will tackle VT100 for T200 in the new year.

Cheers Steve




On Saturday, December 19, 2020, Scott McDonnell 
wrote:

> Alright, sold.  How do I buy the Rex# from you?
>
>
>
> Scott M.
>
>
>
> *From: *Stephen Adolph 
> *Sent: *Saturday, December 19, 2020 7:12 PM
> *To: *m...@bitchin100.com
> *Subject: *Re: [M100] Model 100 Repair - Keyboard not responding,LCD
> missing a column
>
>
>
> Scott,
>
>
>
> After reading your shopping list of wants, I think a REX is a great
> solution, and developing an option ROM is really your best path.
>
> But you don't need to do a rip and replace on the main rom to get there.
>
>
>
> I personally think it is a very bad idea to replace the stock MAIN ROM,
> with REX.
>
>
>
> It was an aspect of the original REX design, with the thinking that, well,
> if you had a huge flash chip what could you do with it?  Yes you could
> store OPTION ROM software, and yes you could back up the RAM nicely.
>
> But what about patched MAIN ROMs?
>
> There are some defects with the original MAIN ROM:
>
> -- Y2K
>
> -- miscalculation of PI (I believe)
>
>
>
> So it sounds like a neat idea. Why not make REX take over the MAIN ROM?
> So I did make that possible however..
>
>
>
> The problem comes when you have an issue with REX, and it is providing the
> boot code.  If REX malfunctions, you can brick your laptop very easily.
>
> So then you need to open it up, insert the original ROM, etc.  A lot of
> pain for not much gain.
>
>
>
> Oh, and by the way all versions of REX fix the Y2K display problem.  So,
> imho, there isn't any real benefit to changing the MAIN ROM, unless having
> Pi to only something like 10 digits isn't good enough;).
>
>
>
> In REX# and REXCPM, I have removed this "rom replacement" function.
>
>
>
> Others may disagree with me.  To each their own.
>
>
>
> Please see further comments below.
>
>
>
> Steve
>
>
>
>
>
>
>
> On Sat, Dec 19, 2020 at 6:35 PM Scott McDonnell <
> mcdonnell.j...@comcast.net> wrote:
>
> Will do. Just so I understand, the Rex replaces the main rom? The M100
> will boot directly from the Rex? And with the Rex, I can customize my own
> applications, autolaunch, etc? This goes into the DVI socket on the bottom?
>
>
>
> REX# (and REXCPM and REXclassic) are all OPTION ROM devices.  They
> generally plug into the option rom socket.
>
> Generally REX makes available to the laptop selectable option rom
> software, and a variety of other functions.
>
>
>
> A typical REX install does NOT require removal of the MAIN ROM, nor is it
> needed.
>
>
>
> I had looked at it before, but the descriptions seem to be written for
> people that are already well into the Model 100 and not very clear to a
> TRS-80 newbie like me. :)
>
>
>
> Yes, my documentation generally assumes a good level of M100 knowledge.  I
> believe there is enough other documentation out there.
>
>
>
>
>
> What I would like to be able to do:
>
> Replace the main ROM
>
>
>
> OK.  Why?  Option ROMs are pretty straightforward to develop.  M100 has a
> good autoboot function built in so you can jump straight into your code.
>
> There is a well used and well documented set of information on how to make
> an option rom.
>
>
>
> Custom menu
>
>
>
> doable via an option ROM.
>
>
>
> My apps not stored in RAM dependent on battery
>
> Again doable via an option rom.  with REX, you can store it in flash, and
> easily re-load bug fix versions as you develop.
>
> If you blow away the main rom you lose all the benefits of having that
> library of software routines to call.
>
>
>
> Autolauch a program at power on (and preferably be able to exit out to
> menu if wanted)
>
> Again, ideal use case for an option rom.
>
>
>
> Ease transfer of files back and forth with a PC (TPDD emulator or
> Trashtalk)
>
>
>
> TS-DOS is also an option rom.
>
>
>
> Thank you to everyone that has replied.
>
>
>
> Really it sounds like a REX is ideal.
>
>
>
>
>

Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a column

[Scott McDonnell]

Alright, sold.  How do I buy the Rex# from you?

Scott M.

From: Stephen Adolph
Sent: Saturday, December 19, 2020 7:12 PM
To: m...@bitchin100.com
Subject: Re: [M100] Model 100 Repair - Keyboard not responding,LCD missing a 
column

Scott,

After reading your shopping list of wants, I think a REX is a great solution, 
and developing an option ROM is really your best path.
But you don't need to do a rip and replace on the main rom to get there.

I personally think it is a very bad idea to replace the stock MAIN ROM, with 
REX.

It was an aspect of the original REX design, with the thinking that, well, if 
you had a huge flash chip what could you do with it?  Yes you could store 
OPTION ROM software, and yes you could back up the RAM nicely.
But what about patched MAIN ROMs?
There are some defects with the original MAIN ROM:
-- Y2K
-- miscalculation of PI (I believe)

So it sounds like a neat idea. Why not make REX take over the MAIN ROM?  So I 
did make that possible however..

The problem comes when you have an issue with REX, and it is providing the boot 
code.  If REX malfunctions, you can brick your laptop very easily.
So then you need to open it up, insert the original ROM, etc.  A lot of pain 
for not much gain.  

Oh, and by the way all versions of REX fix the Y2K display problem.  So, imho, 
there isn't any real benefit to changing the MAIN ROM, unless having Pi to only 
something like 10 digits isn't good enough;).

In REX# and REXCPM, I have removed this "rom replacement" function.

Others may disagree with me.  To each their own.

Please see further comments below.

Steve



On Sat, Dec 19, 2020 at 6:35 PM Scott McDonnell  
wrote:
Will do. Just so I understand, the Rex replaces the main rom? The M100 will 
boot directly from the Rex? And with the Rex, I can customize my own 
applications, autolaunch, etc? This goes into the DVI socket on the bottom?

REX# (and REXCPM and REXclassic) are all OPTION ROM devices.  They generally 
plug into the option rom socket.
Generally REX makes available to the laptop selectable option rom software, and 
a variety of other functions.

A typical REX install does NOT require removal of the MAIN ROM, nor is it 
needed.
 
I had looked at it before, but the descriptions seem to be written for people 
that are already well into the Model 100 and not very clear to a TRS-80 newbie 
like me. :)

Yes, my documentation generally assumes a good level of M100 knowledge.  I 
believe there is enough other documentation out there.
 
 
What I would like to be able to do:
Replace the main ROM

OK.  Why?  Option ROMs are pretty straightforward to develop.  M100 has a good 
autoboot function built in so you can jump straight into your code.
There is a well used and well documented set of information on how to make an 
option rom.
 
Custom menu

doable via an option ROM.
 
My apps not stored in RAM dependent on battery
Again doable via an option rom.  with REX, you can store it in flash, and 
easily re-load bug fix versions as you develop.
If you blow away the main rom you lose all the benefits of having that library 
of software routines to call.

Autolauch a program at power on (and preferably be able to exit out to menu if 
wanted)
Again, ideal use case for an option rom.

Ease transfer of files back and forth with a PC (TPDD emulator or Trashtalk)

TS-DOS is also an option rom.   
 
Thank you to everyone that has replied.

Really it sounds like a REX is ideal.   
 

Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a column

[Stephen Adolph]

Scott,

After reading your shopping list of wants, I think a REX is a great
solution, and developing an option ROM is really your best path.
But you don't need to do a rip and replace on the main rom to get there.

I personally think it is a very bad idea to replace the stock MAIN ROM,
with REX.

It was an aspect of the original REX design, with the thinking that, well,
if you had a huge flash chip what could you do with it?  Yes you could
store OPTION ROM software, and yes you could back up the RAM nicely.
But what about patched MAIN ROMs?
There are some defects with the original MAIN ROM:
-- Y2K
-- miscalculation of PI (I believe)

So it sounds like a neat idea. Why not make REX take over the MAIN ROM?  So
I did make that possible however..

The problem comes when you have an issue with REX, and it is providing the
boot code.  If REX malfunctions, you can brick your laptop very easily.
So then you need to open it up, insert the original ROM, etc.  A lot of
pain for not much gain.

Oh, and by the way all versions of REX fix the Y2K display problem.  So,
imho, there isn't any real benefit to changing the MAIN ROM, unless having
Pi to only something like 10 digits isn't good enough;).

In REX# and REXCPM, I have removed this "rom replacement" function.

Others may disagree with me.  To each their own.

Please see further comments below.

Steve



On Sat, Dec 19, 2020 at 6:35 PM Scott McDonnell 
wrote:

> Will do. Just so I understand, the Rex replaces the main rom? The M100
> will boot directly from the Rex? And with the Rex, I can customize my own
> applications, autolaunch, etc? This goes into the DVI socket on the bottom?
>

REX# (and REXCPM and REXclassic) are all OPTION ROM devices.  They
generally plug into the option rom socket.
Generally REX makes available to the laptop selectable option rom software,
and a variety of other functions.

A typical REX install does NOT require removal of the MAIN ROM, nor is it
needed.

>
>
> I had looked at it before, but the descriptions seem to be written for
> people that are already well into the Model 100 and not very clear to a
> TRS-80 newbie like me. :)
>

Yes, my documentation generally assumes a good level of M100 knowledge.  I
believe there is enough other documentation out there.


>
>
> What I would like to be able to do:
>
> Replace the main ROM
>

OK.  Why?  Option ROMs are pretty straightforward to develop.  M100 has a
good autoboot function built in so you can jump straight into your code.
There is a well used and well documented set of information on how to make
an option rom.


> Custom menu
>

doable via an option ROM.


> My apps not stored in RAM dependent on battery
>
Again doable via an option rom.  with REX, you can store it in flash, and
easily re-load bug fix versions as you develop.
If you blow away the main rom you lose all the benefits of having that
library of software routines to call.

Autolauch a program at power on (and preferably be able to exit out to menu
> if wanted)
>
Again, ideal use case for an option rom.

Ease transfer of files back and forth with a PC (TPDD emulator or Trashtalk)
>

TS-DOS is also an option rom.

>
>
> Thank you to everyone that has replied.
>

Really it sounds like a REX is ideal.

>
>

Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a column

[Scott McDonnell]

NM this question. I think I have gotten a handle on it now. The FlexROM 100 
replaces the main system ROM (only really useful for my M100 with the 
non-standard socket)

The Rex is an option ROM replacement that allows me to store several option 
ROMs at once and also allows me to store my own programs in flash.

With the two together, they form the system you are all describing.

In reading the Rex# instructions, it doesn’t appear that I need to call it to 
get it started (even without a flexROM?)

Thanks again. I am slowly getting up to speed here. I am sure my questions look 
ridiculous to you silverbacks. As I mentioned, the Model 100 is a completely 
new system for me. It’s whole universe is still foreign to me. I’ve never even 
used a TRS-80 of any sort before.

Scott

From: Scott McDonnell
Sent: Saturday, December 19, 2020 6:35 PM
To: m...@bitchin100.com
Subject: Re: [M100] Model 100 Repair - Keyboard not responding,LCD missing a 
column

Will do. Just so I understand, the Rex replaces the main rom? The M100 will 
boot directly from the Rex? And with the Rex, I can customize my own 
applications, autolaunch, etc? This goes into the DVI socket on the bottom?

I had looked at it before, but the descriptions seem to be written for people 
that are already well into the Model 100 and not very clear to a TRS-80 newbie 
like me. :)

What I would like to be able to do:
Replace the main ROM
Custom menu
My apps not stored in RAM dependent on battery
Autolauch a program at power on (and preferably be able to exit out to menu if 
wanted)
Ease transfer of files back and forth with a PC (TPDD emulator or Trashtalk)

Thank you to everyone that has replied.

From: Stephen Adolph
Sent: Saturday, December 19, 2020 6:27 PM
To: m...@bitchin100.com
Subject: Re: [M100] Model 100 Repair - Keyboard not responding,LCD missing a 
column

Scott, I recommend before you jump into a REX solution that you read my REX# 
and REXCPM wiki pages at Bitchin100.
REX Classic is the DIY option, but I no longer support it, and it has known 
defects.
My 2 cents as the designer... Steve



On Sat, Dec 19, 2020 at 6:12 PM Brian White  wrote:
Actually with rex classic you don't even need any rom in the main rom socket so 
you don't need any of those boards, just a single wire from the /CS pin in the 
main rom socket out to the REX. You just can't run the machine *without* the 
rex after that without opening back up to put a rom back. The flexrom board 
just lets you install or remove the rex at will, as well as being re-writable 
itself by being a 28C256.

On Sat, Dec 19, 2020, 6:04 PM Brian White  wrote:

On Sat, Dec 19, 2020, 2:38 PM Scott McDonnell  
wrote:
Now that I have proven out that a 27C256 EPROM is working fine in this one, I 
am going to play around with customizing it. The real ULTIMATE would be to 
replace the ROM with an EEPROM (like 28C256) and add in some type of loader 
where you could update the main firmware over serial. That may not be possible 
because often in these 80’s computers they usually placed some IO address space 
in the ROM area (since write is not possible to the ROM) and decoded it using 
the write signal and address. It was a simple trick for accessing output only 
IO. I am talking out of my rear end right now because I haven’t studied the 
schematic/memory map in detail yet.

http://tandy.wiki/FlexROM_100

http://tandy.wiki/FlexROM_102

Especially in concert with REX Classic

http://tandy.wiki/Building_a_REX
or
arcadeshopper.com sometimes has rex classic pre-built you can just buy.

You'd use the FlexROM_102 in the 100 that has the standard pinout.

If you don't care about using the fully software loadable main rom via REX, and 
only need a plain 28C256 to 27C256 adapter without the /CS breakout remote 
loop, this would be a bit more convenient because it doesn't need a soic-28 
test clip to program it.

http://tandy.wiki/28C256_to_27C256

You just switch a couple jumpers and pop the board right in the programmer.

Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a column

[Scott McDonnell]

Will do. Just so I understand, the Rex replaces the main rom? The M100 will 
boot directly from the Rex? And with the Rex, I can customize my own 
applications, autolaunch, etc? This goes into the DVI socket on the bottom?

I had looked at it before, but the descriptions seem to be written for people 
that are already well into the Model 100 and not very clear to a TRS-80 newbie 
like me. :)

What I would like to be able to do:
Replace the main ROM
Custom menu
My apps not stored in RAM dependent on battery
Autolauch a program at power on (and preferably be able to exit out to menu if 
wanted)
Ease transfer of files back and forth with a PC (TPDD emulator or Trashtalk)

Thank you to everyone that has replied.

From: Stephen Adolph
Sent: Saturday, December 19, 2020 6:27 PM
To: m...@bitchin100.com
Subject: Re: [M100] Model 100 Repair - Keyboard not responding,LCD missing a 
column

Scott, I recommend before you jump into a REX solution that you read my REX# 
and REXCPM wiki pages at Bitchin100.
REX Classic is the DIY option, but I no longer support it, and it has known 
defects.
My 2 cents as the designer... Steve



On Sat, Dec 19, 2020 at 6:12 PM Brian White  wrote:
Actually with rex classic you don't even need any rom in the main rom socket so 
you don't need any of those boards, just a single wire from the /CS pin in the 
main rom socket out to the REX. You just can't run the machine *without* the 
rex after that without opening back up to put a rom back. The flexrom board 
just lets you install or remove the rex at will, as well as being re-writable 
itself by being a 28C256.

On Sat, Dec 19, 2020, 6:04 PM Brian White  wrote:

On Sat, Dec 19, 2020, 2:38 PM Scott McDonnell  
wrote:
Now that I have proven out that a 27C256 EPROM is working fine in this one, I 
am going to play around with customizing it. The real ULTIMATE would be to 
replace the ROM with an EEPROM (like 28C256) and add in some type of loader 
where you could update the main firmware over serial. That may not be possible 
because often in these 80’s computers they usually placed some IO address space 
in the ROM area (since write is not possible to the ROM) and decoded it using 
the write signal and address. It was a simple trick for accessing output only 
IO. I am talking out of my rear end right now because I haven’t studied the 
schematic/memory map in detail yet.

http://tandy.wiki/FlexROM_100

http://tandy.wiki/FlexROM_102

Especially in concert with REX Classic

http://tandy.wiki/Building_a_REX
or
arcadeshopper.com sometimes has rex classic pre-built you can just buy.

You'd use the FlexROM_102 in the 100 that has the standard pinout.

If you don't care about using the fully software loadable main rom via REX, and 
only need a plain 28C256 to 27C256 adapter without the /CS breakout remote 
loop, this would be a bit more convenient because it doesn't need a soic-28 
test clip to program it.

http://tandy.wiki/28C256_to_27C256

You just switch a couple jumpers and pop the board right in the programmer.

Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a column

[Stephen Adolph]

Scott, I recommend before you jump into a REX solution that you read my
REX# and REXCPM wiki pages at Bitchin100.
REX Classic is the DIY option, but I no longer support it, and it has known
defects.
My 2 cents as the designer... Steve



On Sat, Dec 19, 2020 at 6:12 PM Brian White  wrote:

> Actually with rex classic you don't even need any rom in the main rom
> socket so you don't need any of those boards, just a single wire from the
> /CS pin in the main rom socket out to the REX. You just can't run the
> machine *without* the rex after that without opening back up to put a rom
> back. The flexrom board just lets you install or remove the rex at will, as
> well as being re-writable itself by being a 28C256.
>
> On Sat, Dec 19, 2020, 6:04 PM Brian White  wrote:
>
>>
>>
>> On Sat, Dec 19, 2020, 2:38 PM Scott McDonnell 
>> wrote:
>>
>>> Now that I have proven out that a 27C256 EPROM is working fine in this
>>> one, I am going to play around with customizing it. The real ULTIMATE would
>>> be to replace the ROM with an EEPROM (like 28C256) and add in some type of
>>> loader where you could update the main firmware over serial. That may not
>>> be possible because often in these 80’s computers they usually placed some
>>> IO address space in the ROM area (since write is not possible to the ROM)
>>> and decoded it using the write signal and address. It was a simple trick
>>> for accessing output only IO. I am talking out of my rear end right now
>>> because I haven’t studied the schematic/memory map in detail yet.
>>>
>>
>> http://tandy.wiki/FlexROM_100
>>
>> http://tandy.wiki/FlexROM_102
>>
>> Especially in concert with REX Classic
>>
>> http://tandy.wiki/Building_a_REX
>> or
>> arcadeshopper.com sometimes has rex classic pre-built you can just buy.
>>
>> You'd use the FlexROM_102 in the 100 that has the standard pinout.
>>
>> If you don't care about using the fully software loadable main rom via
>> REX, and only need a plain 28C256 to 27C256 adapter without the /CS
>> breakout remote loop, this would be a bit more convenient because it
>> doesn't need a soic-28 test clip to program it.
>>
>> http://tandy.wiki/28C256_to_27C256
>>
>> You just switch a couple jumpers and pop the board right in the
>> programmer.
>>
>>>

Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a column

[Joshua O'Keefe]

On Dec 19, 2020, at 11:38 AM, Scott McDonnell  
wrote:
> 
> BTW, could anyone recommend a new power adapter?

I've been using the below adapter and it's been completely trouble free.
https://www.arcadeshopper.com/wp/store/#!/6v-power-supply-for-models-100-102-200/p/120510370

Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a column

[Brian White]

Actually with rex classic you don't even need any rom in the main rom
socket so you don't need any of those boards, just a single wire from the
/CS pin in the main rom socket out to the REX. You just can't run the
machine *without* the rex after that without opening back up to put a rom
back. The flexrom board just lets you install or remove the rex at will, as
well as being re-writable itself by being a 28C256.

On Sat, Dec 19, 2020, 6:04 PM Brian White  wrote:

>
>
> On Sat, Dec 19, 2020, 2:38 PM Scott McDonnell 
> wrote:
>
>> Now that I have proven out that a 27C256 EPROM is working fine in this
>> one, I am going to play around with customizing it. The real ULTIMATE would
>> be to replace the ROM with an EEPROM (like 28C256) and add in some type of
>> loader where you could update the main firmware over serial. That may not
>> be possible because often in these 80’s computers they usually placed some
>> IO address space in the ROM area (since write is not possible to the ROM)
>> and decoded it using the write signal and address. It was a simple trick
>> for accessing output only IO. I am talking out of my rear end right now
>> because I haven’t studied the schematic/memory map in detail yet.
>>
>
> http://tandy.wiki/FlexROM_100
>
> http://tandy.wiki/FlexROM_102
>
> Especially in concert with REX Classic
>
> http://tandy.wiki/Building_a_REX
> or
> arcadeshopper.com sometimes has rex classic pre-built you can just buy.
>
> You'd use the FlexROM_102 in the 100 that has the standard pinout.
>
> If you don't care about using the fully software loadable main rom via
> REX, and only need a plain 28C256 to 27C256 adapter without the /CS
> breakout remote loop, this would be a bit more convenient because it
> doesn't need a soic-28 test clip to program it.
>
> http://tandy.wiki/28C256_to_27C256
>
> You just switch a couple jumpers and pop the board right in the programmer.
>
>>

Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a column

[Brian White]

On Sat, Dec 19, 2020, 2:38 PM Scott McDonnell 
wrote:

> Now that I have proven out that a 27C256 EPROM is working fine in this
> one, I am going to play around with customizing it. The real ULTIMATE would
> be to replace the ROM with an EEPROM (like 28C256) and add in some type of
> loader where you could update the main firmware over serial. That may not
> be possible because often in these 80’s computers they usually placed some
> IO address space in the ROM area (since write is not possible to the ROM)
> and decoded it using the write signal and address. It was a simple trick
> for accessing output only IO. I am talking out of my rear end right now
> because I haven’t studied the schematic/memory map in detail yet.
>

http://tandy.wiki/FlexROM_100

http://tandy.wiki/FlexROM_102

Especially in concert with REX Classic

http://tandy.wiki/Building_a_REX
or
arcadeshopper.com sometimes has rex classic pre-built you can just buy.

You'd use the FlexROM_102 in the 100 that has the standard pinout.

If you don't care about using the fully software loadable main rom via REX,
and only need a plain 28C256 to 27C256 adapter without the /CS breakout
remote loop, this would be a bit more convenient because it doesn't need a
soic-28 test clip to program it.

http://tandy.wiki/28C256_to_27C256

You just switch a couple jumpers and pop the board right in the programmer.

>

Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a column

[Josh Malone]

On Thu, Dec 17, 2020 at 2:08 PM mcdonnell.junk
 wrote:
>
> And, well, I *did* break a trace and possibly pulled out a barrel. Lol. That 
> was likely my impatience and not the tool. I did test the force requir3d to 
> pop the chip out before prying on it and it came out easy, so I thought all 
> was good.

Yeah - impatience got me when I was working in my ZX Spectrum +2 a
couple months ago. Lifted 2 pads when removing a PLA because I was
hungry and wanted to finish the job before dinner. D'oh!

-Josh

Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a column

[mcdonnell.junk]

Of course! I completely understand. Just wanted to toss that out there in case 
anyone was afraid to make suggestions for rework to me.And, well, I *did* break 
a trace and possibly pulled out a barrel. Lol. That was likely my impatience 
and not the tool. I did test the force requir3d to pop the chip out before 
prying on it and it came out easy, so I thought all was good.Not a huge deal, 
though. I'll find it and slip 32 awg though the via to fix it or just jumper 
and stake wire on the top side too.Sent from my T-Mobile 4G LTE Device
 Original message From: Josh Malone  
Date: 12/17/20  1:34 PM  (GMT-05:00) To: m...@bitchin100.com Subject: Re: 
[M100] Model 100 Repair - Keyboard not responding,
  LCD missing a column On Thu, Dec 17, 2020 at 11:30 AM 
mcdonnell.junk wrote:>> I am an electrical 
engineer. That doesn't mean I am an expert in all things (or even a lot of 
things), but my home lab is very well equipped with various scopes, logic 
analyzers, eeprom and various other programmers, an eeprom emulator, processor 
emulators, hot air rework station, electrical desoldering pump, microscopes, 
hakko temp controlled irons, etc and at work I have access to pretty much 
anything.>> The problem is sometimes my impatience, not knowledge. :)>> Point 
is that I do have the right tools and experience to work on this stuff. But the 
M100 is a new computer for me. I was a Commodore kid.>> If I break traces, I am 
not freaked out by that. I can repair them properly. Of course, I would rather 
not!>> Power supply rails were fine, btw. Of course that doesn't mean previous 
owner didn't plug in 12V or  reverse polarity adapter and just didn't tell me. 
I bought it broken along with the working unit. But power supplies are stable 
at the moment.>Cool! I never know what a person's comfort level w/ rework is 
when thepost asking for repair tips. In case you weren't aware, the M100service 
manual is excellent for troubleshooting issues w/ the 
machine.https://archive.org/details/TandyM100ServiceManual

Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a column

[mcdonnell.junk]

For sure. The back of my board is covered in a thick layer of flux and it looks 
like the type that likes to eat traces over time and sometimes even becomes 
conductive. Typical 80s flux. I wish I had a board washer at home because they 
don't like us playing with the one at work. I'll just have to drown it in 
alcohol. The board, I mean. Heh...Scott M.Sent from my T-Mobile 4G LTE Device
 Original message From: Jeffrey Birt  
Date: 12/17/20  1:15 PM  (GMT-05:00) To: m...@bitchin100.com Subject: Re: 
[M100] Model 100 Repair - Keyboard not responding, LCD missing a column In the 
past few weeks I have seen a couple of very odd problems with M100s.  #1) One 
tow of keys (from matrix point of view) showing up as the previous row (like 
row 2 showing up as row 3). Looked at with a logic analyzer and you could see 
the signal from each row. However, this was not a simple short it was a one-way 
phenomenon. Pressing a row 3 key did not show a signal from both rows on the 
LA. I pulled all components related to KB scanning and could still measure a 
‘short’, which acted like a capacitance, between the two rows. This was caused 
by some contamination on the PCB. Cleaned the PCB, reinstall components and it 
was fine. #2) LCD corruption, serial loop back failure and 20ma of excessive 
current draw. The LCD had missing blocks, areas of gibberish and some areas 
were OK. Otherwise, it seemed to work fine. Trouble traced down to data bus 
contention caused by M23. It was amazing it worked at all.  #3) T25 in the 
reset circuit died while I was testing something unrelated. The particular M100 
failed to boot sometimes but I attributed it to my test set up. When it quit 
booting all together then I was forced to look for the root cause. T25 measured 
fine in circuit with the ‘diode test’ on the multimeter but was leaking enough 
to have 0.6v on the base with 0V being applied my M28. This was not letting C78 
to charge up, it was only getting to about 0.8V and the machine stayed in 
reset.Point is very strange things can happen on these boards. My rule of thumb 
on a vintage computer is to check voltages, the reset circuit, clock, and then 
for bus activity. A logic probe or LA can mislead you with bus activity as it 
will now show you issues with marginal voltage levels or bun contention.  
FWIW,Jeff Birt (Hey Birt!) From: M100  On 
Behalf Of Stephen AdolphSent: Thursday, December 17, 2020 10:38 AMTo: 
m100@bitchin100.comSubject: Re: [M100] Model 100 Repair - Keyboard not 
responding, LCD missing a column Scott, if you have a scope that will be 
extremely helpful.  In my experience you can sorta tell when the CPU is 
booting, and has access to RAM and ROM, by looking at the signals on the bus. I 
typically check out the signals at the main ROM first, then go to the nearest 
RAM.  Those parts are at the "end of the line" for the address/data bus, so if 
you have an open trace, you will see it there.   If the Main ROM and 1st RAM 
have good signals, it should boot.  Also worth it to check that the CLK signal 
on the 8085 is showing 2.45 MHz. I also check /RD, ./WR, IO/M etc. good luck, 
and ask questions.Steve 

Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a column

[Jeffrey Birt]

In the past few weeks I have seen a couple of very odd problems with M100s. 

 

#1) One tow of keys (from matrix point of view) showing up as the previous row 
(like row 2 showing up as row 3). Looked at with a logic analyzer and you could 
see the signal from each row. However, this was not a simple short it was a 
one-way phenomenon. Pressing a row 3 key did not show a signal from both rows 
on the LA. I pulled all components related to KB scanning and could still 
measure a ‘short’, which acted like a capacitance, between the two rows. This 
was caused by some contamination on the PCB. Cleaned the PCB, reinstall 
components and it was fine.

 

#2) LCD corruption, serial loop back failure and 20ma of excessive current 
draw. The LCD had missing blocks, areas of gibberish and some areas were OK. 
Otherwise, it seemed to work fine. Trouble traced down to data bus contention 
caused by M23. It was amazing it worked at all. 

 

#3) T25 in the reset circuit died while I was testing something unrelated. The 
particular M100 failed to boot sometimes but I attributed it to my test set up. 
When it quit booting all together then I was forced to look for the root cause. 
T25 measured fine in circuit with the ‘diode test’ on the multimeter but was 
leaking enough to have 0.6v on the base with 0V being applied my M28. This was 
not letting C78 to charge up, it was only getting to about 0.8V and the machine 
stayed in reset.

Point is very strange things can happen on these boards. My rule of thumb on a 
vintage computer is to check voltages, the reset circuit, clock, and then for 
bus activity. A logic probe or LA can mislead you with bus activity as it will 
now show you issues with marginal voltage levels or bun contention. 

 

FWIW,

Jeff Birt (Hey Birt!)

 

From: M100  On Behalf Of Stephen Adolph
Sent: Thursday, December 17, 2020 10:38 AM
To: m...@bitchin100.com
Subject: Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a 
column

 

Scott, if you have a scope that will be extremely helpful.  In my experience 
you can sorta tell when the CPU is booting, and has access to RAM and ROM, by 
looking at the signals on the bus. I typically check out the signals at the 
main ROM first, then go to the nearest RAM.  Those parts are at the "end of the 
line" for the address/data bus, so if you have an open trace, you will see it 
there.  

 

If the Main ROM and 1st RAM have good signals, it should boot.  Also worth it 
to check that the CLK signal on the 8085 is showing 2.45 MHz.

 

I also check /RD, ./WR, IO/M etc.

 

good luck, and ask questions.

Steve

 

Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a column

[Stephen Adolph]

Scott, if you have a scope that will be extremely helpful.  In my
experience you can sorta tell when the CPU is booting, and has access to
RAM and ROM, by looking at the signals on the bus. I typically check out
the signals at the main ROM first, then go to the nearest RAM.  Those parts
are at the "end of the line" for the address/data bus, so if you have an
open trace, you will see it there.

If the Main ROM and 1st RAM have good signals, it should boot.  Also worth
it to check that the CLK signal on the 8085 is showing 2.45 MHz.

I also check /RD, ./WR, IO/M etc.

good luck, and ask questions.
Steve

On Thu, Dec 17, 2020 at 11:30 AM mcdonnell.junk 
wrote:

> I am an electrical engineer. That doesn't mean I am an expert in all
> things (or even a lot of things), but my home lab is very well equipped
> with various scopes, logic analyzers, eeprom and various other programmers,
> an eeprom emulator, processor emulators, hot air rework station, electrical
> desoldering pump, microscopes, hakko temp controlled irons, etc and at
> work I have access to pretty much anything.
>
> The problem is sometimes my impatience, not knowledge. :)
>
> Point is that I do have the right tools and experience to work on this
> stuff. But the M100 is a new computer for me. I was a Commodore kid.
>
> If I break traces, I am not freaked out by that. I can repair them
> properly. Of course, I would rather not!
>
> Power supply rails were fine, btw. Of course that doesn't mean previous
> owner didn't plug in 12V or  reverse polarity adapter and just didn't tell
> me. I bought it broken along with the working unit. But power supplies are
> stable at the moment.
>
> Scott M.
>
>
>
> Sent from my T-Mobile 4G LTE Device
>
>
>  Original message 
> From: Josh Malone 
> Date: 12/17/20 9:18 AM (GMT-05:00)
> To: m...@bitchin100.com
> Subject: Re: [M100] Model 100 Repair - Keyboard not responding, LCD
> missing a column
>
> Sorry for not chiming in yesterday. Before taking the soldering iron to
> anything, it's good to always check the power supply rails for proper
> voltages and remove the optional RAM modules (as I see you have done). What
> sort of tools do you have available? (oscilloscope, multimeter,
> temp-controlled soldering station) Given the age and relatively cheap
> construction of these machines, it's very easy to do more damage when
> trying to repair them.
>
> -Josh
>
>>

Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a column

[mcdonnell.junk]

I am an electrical engineer. That doesn't mean I am an expert in all things (or 
even a lot of things), but my home lab is very well equipped with various 
scopes, logic analyzers, eeprom and various other programmers, an eeprom 
emulator, processor emulators, hot air rework station, electrical desoldering 
pump, microscopes, hakko temp controlled irons, etc and at work I have 
access to pretty much anything.The problem is sometimes my impatience, not 
knowledge. :) Point is that I do have the right tools and experience to work on 
this stuff. But the M100 is a new computer for me. I was a Commodore kid.If I 
break traces, I am not freaked out by that. I can repair them properly. Of 
course, I would rather not!Power supply rails were fine, btw. Of course that 
doesn't mean previous owner didn't plug in 12V or  reverse polarity adapter and 
just didn't tell me. I bought it broken along with the working unit. But power 
supplies are stable at the moment.Scott M.Sent from my T-Mobile 4G LTE Device
 Original message From: Josh Malone  
Date: 12/17/20  9:18 AM  (GMT-05:00) To: m...@bitchin100.com Subject: Re: 
[M100] Model 100 Repair - Keyboard not responding, LCD missing a column Sorry 
for not chiming in yesterday. Before taking the soldering iron to anything, 
it's good to always check the power supply rails for proper voltages and remove 
the optional RAM modules (as I see you have done). What sort of tools do you 
have available? (oscilloscope, multimeter, temp-controlled soldering station) 
Given the age and relatively cheap construction of these machines, it's very 
easy to do more damage when trying to repair them.-Josh

Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a column

[Josh Malone]

Sorry for not chiming in yesterday. Before taking the soldering iron to
anything, it's good to always check the power supply rails for proper
voltages and remove the optional RAM modules (as I see you have done). What
sort of tools do you have available? (oscilloscope, multimeter,
temp-controlled soldering station) Given the age and relatively cheap
construction of these machines, it's very easy to do more damage when
trying to repair them.

-Josh

>

Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a column

[B4 Me100]

Yes it could be a broken  trace they are very fragile, the boards are very
low quality and 35+ years old :)

There are quite a surprising number of things out there for the 100/102 from
modern software to new hardware add on designs.  There are a few repair
videos on YT if you need extra information.

From:  M100  on behalf of Scott McDonnell

Reply-To:  "m...@bitchin100.com" 
Date:  Wednesday, December 16, 2020 at 8:06 PM
To:  "m...@bitchin100.com" 
Subject:  Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing
a column

> I think you may be right. So, I went ahead and did that since it seemed quick
> and easy with a good desoldering pump. Unfortunately, I think some traces were
> damaged despite my being careful and using a good tool. At least one was
> obvious, but I didn¹t spot it until after I was finished (means I probably
> caused it.) I fixed that one, but I get nothing now so I suspect there are
> more I can¹t see with the naked eye. I will need to take the meter to the
> lines tomorrow and check for broken traces. Perhaps I blew a barrel from
> bottom to top side and will need to fix that. Traces seem very fragile.
>  
> Anyway on the right track now. I would still like to replace my ROM to take
> advantage of the fact that this model is compatible with a 27C256. These are
> my very first M100¹s, so I just don¹t know what is out there or where to find
> them. I tried looking through the Club100 site and I have probably looked at
> the thing I want a 100 times and just not recognizing it. Would really
> appreciate a suggestion.
>  
> Goodnight folks. Thank you for putting up with me tonight!
>  
> Scott M.
>  
> 
> From: B4 Me100 <mailto:b4me...@hotmail.com>
> Sent: Wednesday, December 16, 2020 10:01 PM
> To: m...@bitchin100.com
> Subject: Re: [M100] Model 100 Repair - Keyboard not responding,LCD missing a
> column
>  
> 
> Hi
> 
>  
> 
> I suspect the standard RAM is probably bad and the first place to look.I
> would pull that one out, as well as all the other RAM, and try another Œgood¹
> one in that location.   It should boot beyond the confused LCD screen.  I
> doubt the ROM is bad if it was broken nothing would work I have never seen a
> bad ROM but have replaced quite a lot of ceramic RAM modules ­ I think I have
> 7 bad modules on my bench, 4 from one machine :)
> 
>  
> 
> The standard RAM module, the one that is soldered in, is where all the data is
> stored that controls the system.  If it is bad nothing works or at least it
> will be flakey.  Removing the other socketed RAM will not impact the system
> they are optional and are not needed to run the machine.   The machine appears
> to boot quite far into the ROM and I think after the LCD is turned on it
> starts to configure the standard RAM ready for file storage and general
> program use, which is where it appears to be failing.
> 
>  
> 
> I would be tempted to replace all the ceramic OEM RAM modules with more modern
> versions just to make sure the machine is reliable for your application.  I
> have had one machine where they died in sequence ­ almost.
> 
>  
> 
> Possibly first recap the boards to make sure the voltages are healthy and look
> for corroded traces - another very common fault.
> 
>  
> 
>  
> 
> From: M100  on behalf of Scott McDonnell
> 
> Reply-To: "m...@bitchin100.com" 
> Date: Wednesday, December 16, 2020 at 6:28 PM
> To: "m...@bitchin100.com" 
> Subject: Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a
> column
> 
>  
>> 
>> Well, good news and bad news. I cracked open the working M100 and they are
>> different generations of boards, so the ROMs are different. The good news is
>> that the ³bad² M100 has the type of ROM that can be replaced with a 27C256. I
>> only have some 28C256s sitting around so I ordered some 27C256s (don¹t want
>> to bodge the board to make a 28C256 work just out of impatience).
>>  
>> As soon as I can find a ROM image (can anyone point me to the location of
>> these and recommend an updated custom ROM?) I will burn an eprom and give
>> that a try. I do have a feeling that this is the problem.
>>  
>> For reference, my working M100 has board PLX110CH1X and the bad M100 has
>> PLX110EH1X. The RAM modules in the working unit also appear to be
>> after-market and my PIA is socketed, so someone worked on this before.
>>  
>> Bad is on the left, good is on the right:
>>  
>>  
>>  
>>  
>> 
>> From: Scott McDonnell <mailto:mcdonnell.j...@comcast.net>
>> Sent: Wednesday, December 16, 2020 8:43 PM
>> To: m...@bitchin100.com
>> Subject: Re: [

Re: [M100] Model 100 Repair - Keyboard not responding, LCD missing a column

[Scott McDonnell]

I should have added that the reason I suspect the one RAM module soldered to 
the board is that I tried removing the other 3 (this has all 32K of memory 
installed) and nothing changed. My next step was to desolder the RAM module, 
install socket strips and then try one of the other RAM modules in the main 
slot.

I am also planning to try taking the ROM from my working M100 and installing 
that in the non-working unit to see if it is the ROM.

Any other ideas would be appreciated.

Scott M.

From: Scott McDonnell
Sent: Wednesday, December 16, 2020 8:06 PM
To: m...@bitchin100.com
Subject: [M100] Model 100 Repair - Keyboard not responding,LCD missing a column

I mentioned before that I bought two Model 100s and that one of them is not 
working. Here is a description:

The computer boots sometimes. When it doesn’t you get just a dark screen. 
Turning on and off a few times, you get the menu. However, only Schedule is 
populated (in the first slot which would normally be BASIC…) and there is no 
“SELECT” at the bottom. No response from any keyboard keys.

The above leads me to believe that it is not really that the keyboard is not 
working, but that the computer encounters a fault while loading the menu and 
never completes to the point that I could use the keyboard. That leads me to 
think maybe a faulty ROM or possibly the one RAM module that is soldered to the 
board. I wonder what others might think?

Second problem:
The LCD is missing a column. I got brave and disassembled the LCD to clean the 
contacts. The good news is that I think I fixed that missing column. The bad 
news is that now the LCD is all jumbled mess. I don’t think it is alignment 
since some text displays perfectly fine is just the right spots. I think it is 
a lack of pressure. Planning to install some thin foam inside the metal 
surround to create more pressure on the LCD contacts. I think the metal twist 
tabs are just not cutting it anymore. I will update whether this works or not.

I plan to recap both of these and replace the NiCad batteries, but I don’t 
believe that either of them currently have any issues with those parts. If 
anyone has experienced the above problem, I would very much like to hear what 
you have done to fix it.

Scott M.