Re: [M100] Another slabtop? Or pc screen extension?

[George Goodman]

I have a Raspberry Pi 400 and like it quite a lot. I have a 128Gb microSD card 
in it and am syncing it with my Dropbox account (using rclone).

...and I've had no problems with the keyboard. It certainly isn't a solid, 
clicky mechanical :) but for a downsized, low-travel keyboard it isn't bad. I 
find it usable and can touch type without more errors than usual.

george g.

On Fri, Aug 19, 2022, at 7:55 PM, Ariel Millennium Thornton wrote:
> The Raspberry Pi 400?
> 
> I got one of those last summer and poked at it daily for light office
> stuff.  It's a great little computer with a fantastic profile.
> Aesthetically, it feels like it's begging me to stick it and a display
> to a board and turn it into a slabtop.
> 
> However, the keyboard mechanism feels like it isn't up to the task of
> even light writing or occasional programming.  The keys don't always
> register when pressed, even though the keys feel great, and the D key in
> particular on mine has been that way since I took it out of the box.
> 
> ~ArielMT
> 
> 
> On Fri, 19 Aug 2022 18:12:39 -0400, Jeff Gonzales wrote:
> 
> > Anyone try the red and white Raspberry PI PC?
> > 
> > On Fri, Aug 19, 2022, 5:26 PM John R. Hogerhuis 
> > wrote:
> > 
> > > What was wrong with it? I watched a YouTube review, the guy thought
> > > the build quality was great but that it needed dedicated software
> > > (presumably on the desktop side).
> > >
> > > -- John.
> > >
> > > On Fri, Aug 19, 2022, 1:17 PM Alastair Wiggins
> > >  wrote:
> > >
> > >> Hi,
> > >>
> > >> I bought one from Amazon. It wasn't cheap and the quality was
> > >> awful.
> > >>
> > >> Returned to Amazon for a full refund!
> > >>
> > >> Alastair
> > >>
> > >>
> > >>>
> > >>> -- Forwarded message --
> > >>> From: "John R. Hogerhuis" 
> > >>> To: m...@bitchin100.com
> > >>> Cc:
> > >>> Bcc:
> > >>> Date: Thu, 18 Aug 2022 13:16:48 -0700
> > >>> Subject: [M100] Another slabtop? Or pc screen extension?
> > >>> Ain't that pretty?
> > >>>
> > >>>
> > >>> https://gagadget.com/en/156042-ficihip-mechanical-keyboard-has-an-integrated-126-inch-touchscreen-display/
> > >>>
> > >>> Not sure what it can actually do.
> > >>>
> > >>> -- John.
> > >>>
> > >>>
> > >>>
> > >>>
> > >>>
> 

Re: [M100] is the list actually working?

[George Goodman]

Yep. Got it. I'm using Fastmail, not Gmail.

george g.


On Tue, May 3, 2022, at 6:22 AM, Stephen Adolph wrote:
> I find myself wondering if the mailing list is now becoming very unreliable.
> If this message gets through please respond.
> thanks
> Steve

Re: [M100] 5MHz and RAM in M100/T102

[George Goodman]

Hi Steve,

This sounds like putting afterburners on the M100 (well, maybe more like 
replacing the donkey with a mule :) and the boost in performance would be 
interesting to see. I wonder:

1. Is there any impact on any of the I/Os (RS-232, Centronix port, etc.)?
2. Have you seen any appreciable impact on battery life? I’m guessing you 
haven’t even run the reworked units off of wall power.

Thanks for the journal of this endeavor. I look forward to the next chapter.

george g.

> On 10Nov2021, at 4:26 AM, Stephen Adolph  wrote:
> 
> List has been a bit quiet lately, so I thought.. why not share something 
> interesting that I just learned?
> 
> I have been toying quite a bit with 5MHz operation in M100 mostly but also in 
> T102.
> In M100, I have been using 5MHz upgrades of a few different types, but they 
> all involve replacing the SRAM because the stock set up can't work that fast.
> 
> Same on T102.  I did an initial attempt, and it failed, and I set it aside 
> for a while without digging in to it to understand why.
> 
> When I build REX#/REXCPM, I now have a 5MHz M100 with a test jig attached 
> that lets me program the CPLD, test, and load the flash in the same setup.  
> This is a good practical use for 5MHz as it cuts the test time by about 50%.  
> Not quite 50% but almost.
> 
> I have a "parts machine" T102 however that was gathering dust and I thought - 
> why not revive it and see what exactly is the problem with the T102 and 5MHz. 
>  This lead to an interesting discovery (at least to me).
> 
> The reason why the T102 can't run at 5MHz is again the SRAM - but the reason 
> is actually not the speed of the RAM.  It is actually how the chip select 
> circuit is implemented.I noticed that if I compare the SRAM chip select 
> signals to the main ROM chip select, they had different timing.  The RAM chip 
> select was timed to toggle with the edge of both /RD and /WR (which is late 
> in the cycle), whereas the chip select for the main ROM toggles with the 
> actual start of the machine cycle (with ALE, IO/M and all the Address lines).
> 
> This is totally unnecessary, and really impairs the SRAM!  It happens to work 
> at 2.5MHz but just not any faster.  The reason why this is not optimal is 
> because all SRAM chips have a delayed response to the chip select line.  It 
> is better to use /OE to control the "read output" of the RAM chip synchronous 
> with /RD with the /CS line toggling early, as opposed to grounding the /OE 
> signal, and toggling /CS with /RD.
> 
> To prove this out, I made a small change to my donor T102.  
> 1)  Pin 22 on the HM6264 SRAM is /OE and it is grounded.  I cut that track 
> (in 4 places for 4 SRAMs)
> 2) I connected each SRAM pin 22 to /RD (found at the main ROM pin 22).
> 3) I removed the A* signal from the M37 NAND gate that is used to control 
> chip select timing.  I lifted pin 9 of M37 and connected the pin to +5V.
> 
> Voila!  T102 runs at 5MHz with stock SRAM (in this case 150nsec rated).
> 
> 
> Disclaimer:  I actually have replaced the Main ROM with a 150 nsec 27C256, 
> because a long time ago I snipped out the original main ROM.  Not really sure 
> if the original main ROM is quick enough but I'll find that out shortly.
> 
> 
> So, a simple change allows the T102 installed SRAM to run at 5MHz.  Does the 
> same issue impair the M100?
> 
> The answer is - YES!.  in the M100, the A* signal is again used to control 
> the chip select timing, as can be seen at M3 and M4.  Question is - can the 
> timing be corrected easily and still maintain the function of the memory?
> 
> I think this answer is NO.  There isn't a spare unused RAM control that is 
> simply grounded on the stock 8K RAM modules.  On the stock 8K module, the 
> chip select lines solely control read output.  If we try to advance the 
> timing of the stock 8k module, in the early part of the memory read cycle the 
> SRAM would not be synchronized with /RD and would be trying to put data on 
> the bus when the main bus driver M2 is still itself pushing data on the bus.  
> I think this conflict would be undesireable.
> 
> I may try it out, however.  ;)
> 
> So, my observations about running 5MHz are as follows
> 
> 1) the major ICs all seem to handle 5MHz just fine.
> 
> 2) in M100, you have to replace the original main ROM as it is too slow.  
> That is relatively painless as the main ROM is socketed.  You also need to 
> replace the SRAM modules, which is a pain to be honest since at least one 
> module is soldered in.. REXCPM is a convenient way to disable and replace the 
> internal SRAM.
> 
> 3) in T102,  the main ROM (TBC) and SRAM all support 5MHz as well, but a 
> small circuit change is needed to free up the SRAM speed.  OR - again REXCPM 
> is a convenient way around the SRAM mod since it disables internal SRAM and 
> is itself fast.
> 
> 
> Is 5MHz practical?  Getting there.  I certainly like it.  I think I will 
> re-attempt a 5MHz upgrade on one of my good T102 and start using 

Re: [M100] M100 display suddenly less visible

[George Goodman]

Hi Jeff,

Thanks for showing me my next step (contact cleaner). If that doesn’t do the 
trick, I’ll use the approach you describe for getting the vintage pot off the 
board and pursue Brad’s clever fab.

george g.

> On 08Nov2021, at 5:05 AM, Jeffrey Birt  wrote:
> 
> The easiest way to pull these pots is to use a large soldering iron tip and a 
> big blob of solder to heat all 3-4 terminals at once. It is easy to pull out 
> when all leads are hot at once. They you can use solder braid or a solder 
> sucker to clean out the holes.
> 
> Most often you can take the knob loose and drip some contact cleaner into the 
> pot and rotate it back and forth to revive it. This does not always work but 
> it does most of the time.
>  
> Jeff Birt
>  
> From: M100  On Behalf Of George Goodman
> Sent: Sunday, November 7, 2021 3:57 PM
> To: m100@lists.bitchin100.com
> Subject: Re: [M100] M100 display suddenly less visible
>  
> FYI, it appears the pot is dead, dead, dead (well, it isn't potentiating, 
> just letting a rather small bit through). That pot is so small and so very 
> well soldered to the board that I don't think I can do anything about it. It 
> appears that this M100 will become my donor.
>  
> My second system arrives this week.
>  
> Thanks for all the help, folks!
>  
> george g.
>  
> --- 
> Please note that this email is coming from my new account. Change the contact 
> information you have for me to send emails to georgeogood...@orgoodman.net 
> <mailto:georgeogood...@orgoodman.net>
> Thanks!
>  
>  
> On Thu, Nov 4, 2021, at 12:19 PM, George Goodman wrote:
>> Hi all,
>>  
>> My M100 display seems to have taken a turn for the dim. See the images in 
>> this shared folder —> 
>> https://www.dropbox.com/sh/y1cpftct6dgqy2j/AAAEb3PmIC1b30qh7FV_WX4ea?dl=0 
>> <https://www.dropbox.com/sh/y1cpftct6dgqy2j/AAAEb3PmIC1b30qh7FV_WX4ea?dl=0> 
>>  
>> I can’t point to anything that happened. I started an install of TS-DOS from 
>> my Backpack and, once the Initial Program Load began, stepped away from my 
>> desk to get a glass of water. When I returned a few minutes later I thought 
>> the M100 had flat out died. I removed the Backpack and tried turning the 
>> M111 on and off and even did a hard reset. No joy…I thought.
>>  
>> I happened to sit down at my desk and catch a more extreme viewing angle of 
>> the display. That’s when I realized that there was just a display issue. I 
>> verified that I can start up Basic, make the system beep, open Text, etc. 
>> However, I haven’t found anything that will get the display back to good 
>> viewing from overhead.
>>  
>> BTW, I did try the contrast dial and that didn’t have any impact. The images 
>> in that shared folder were taken with the contrast at its highest.
>>  
>> Does anyone have suggestions for debugging and fixing this?
>>  
>> Thanks,
>>  
>> george g.

Re: [M100] M100 display suddenly less visible

[George Goodman]

Well, Brad, that's a lovely solution to the problem. I'm going to think about 
it (even though I have a second M100 coming this week, I don't mind 
resuscitating the donor-to-be!

Thanks much for the idea and the solution!

george g.

On Sun, Nov 7, 2021, at 3:19 PM, Brad Grier wrote:
> Hi George, I too had a pot on my NEC 8201 that had died, so I fabricated a 
> tray to allow new pots to be used to replace these old ones that aren't made 
> anymore.
> 
> More detail here on my first version, if you're interested: 
> http://stuff.bradgrier.com/docs/drop-in-vr1-documentation/how-to-install-the-drop-inn-vr1-replacement-pot/
> I do have a newer version in the works that is a bit simpler to work with. 
> Happy to answer any questions...
> 
> --Brad
> 
> On Sun, Nov 7, 2021 at 2:57 PM George Goodman  
> wrote:
>> __
>> FYI, it appears the pot is dead, dead, dead (well, it isn't potentiating, 
>> just letting a rather small bit through). That pot is so small and so very 
>> well soldered to the board that I don't think I can do anything about it. It 
>> appears that this M100 will become my donor.
>> 
>> My second system arrives this week.
>> 
>> Thanks for all the help, folks!
>> 
>> george g.
>> 
>> --- 
>> Please note that this email is coming from my new account. Change the 
>> contact information you have for me to send emails to 
>> georgeogood...@orgoodman.net
>> Thanks!
>> 
>> 
>> On Thu, Nov 4, 2021, at 12:19 PM, George Goodman wrote:
>>> Hi all,
>>> 
>>> My M100 display seems to have taken a turn for the dim. See the images in 
>>> this shared folder —> 
>>> *https://www.dropbox.com/sh/y1cpftct6dgqy2j/AAAEb3PmIC1b30qh7FV_WX4ea?dl=0 *
>>> **
>>> I can’t point to anything that happened. I started an install of TS-DOS 
>>> from my Backpack and, once the Initial Program Load began, stepped away 
>>> from my desk to get a glass of water. When I returned a few minutes later I 
>>> thought the M100 had flat out died. I removed the Backpack and tried 
>>> turning the M111 on and off and even did a hard reset. No joy…I thought.
>>> 
>>> I happened to sit down at my desk and catch a more extreme viewing angle of 
>>> the display. That’s when I realized that there was just a display issue. I 
>>> verified that I can start up Basic, make the system beep, open Text, etc. 
>>> However, I haven’t found anything that will get the display back to good 
>>> viewing from overhead.
>>> 
>>> BTW, I did try the contrast dial and that didn’t have any impact. The 
>>> images in that shared folder were taken with the contrast at its highest.
>>> 
>>> Does anyone have suggestions for debugging and fixing this?
>>> 
>>> Thanks,
>>> 
>>> george g.
>> 
> 
> 
> -- 
> -- 
> Brad Grier
> 
> 

Re: [M100] M100 display suddenly less visible

[George Goodman]

FYI, it appears the pot is dead, dead, dead (well, it isn't potentiating, just 
letting a rather small bit through). That pot is so small and so very well 
soldered to the board that I don't think I can do anything about it. It appears 
that this M100 will become my donor.

My second system arrives this week.

Thanks for all the help, folks!

george g.

--- 
Please note that this email is coming from my new account. Change the contact 
information you have for me to send emails to georgeogood...@orgoodman.net
Thanks!


On Thu, Nov 4, 2021, at 12:19 PM, George Goodman wrote:
> Hi all,
> 
> My M100 display seems to have taken a turn for the dim. See the images in 
> this shared folder —> 
> *https://www.dropbox.com/sh/y1cpftct6dgqy2j/AAAEb3PmIC1b30qh7FV_WX4ea?dl=0 *
> **
> I can’t point to anything that happened. I started an install of TS-DOS from 
> my Backpack and, once the Initial Program Load began, stepped away from my 
> desk to get a glass of water. When I returned a few minutes later I thought 
> the M100 had flat out died. I removed the Backpack and tried turning the M111 
> on and off and even did a hard reset. No joy…I thought.
> 
> I happened to sit down at my desk and catch a more extreme viewing angle of 
> the display. That’s when I realized that there was just a display issue. I 
> verified that I can start up Basic, make the system beep, open Text, etc. 
> However, I haven’t found anything that will get the display back to good 
> viewing from overhead.
> 
> BTW, I did try the contrast dial and that didn’t have any impact. The images 
> in that shared folder were taken with the contrast at its highest.
> 
> Does anyone have suggestions for debugging and fixing this?
> 
> Thanks,
> 
> george g.

Re: [M100] M100 display suddenly less visible

[George Goodman]

Hi Jeff,

Well, I'll make cap checks one of the first things I do with my next M100.

Also, both my son and I will  be checking out both your and Josh's videos 
before we crack the case open tomorrow.

Thanks for the much-needed pointers,

george g.
--- 
Please note that this email is coming from my new account. Change the contact 
information you have for me to send emails to georgeogood...@orgoodman.net
Thanks!


On Fri, Nov 5, 2021, at 5:28 AM, Jeffrey Birt wrote:
> Hi George,
>  
> As Josh mentioned the power supply is a common problem on these machines. The 
> electrolytic capacitors leak and their value changes. The M100 is one of the 
> few machines I consider a must for recapping. Using the Backpack, means using 
> the serial port which places an additional load on the -5V supply (in 
> addition to the screen.) I suspect your -5V was right on the edge of failing 
> and this pushed it over.
>  
> I think Josh and I have both done videos about the recapping process if that 
> would be of help.
>  
> Jeff Birt
>  
> *From:* M100  *On Behalf Of *George Goodman
> *Sent:* Thursday, November 4, 2021 2:19 PM
> *To:* m100@lists.bitchin100.com
> *Subject:* [M100] M100 display suddenly less visible
> 
>  
> Hi all,
>  
> My M100 display seems to have taken a turn for the dim. See the images in 
> this shared folder —> 
> *https://www.dropbox.com/sh/y1cpftct6dgqy2j/AAAEb3PmIC1b30qh7FV_WX4ea?dl=0 *
>  
> I can’t point to anything that happened. I started an install of TS-DOS from 
> my Backpack and, once the Initial Program Load began, stepped away from my 
> desk to get a glass of water. When I returned a few minutes later I thought 
> the M100 had flat out died. I removed the Backpack and tried turning the M111 
> on and off and even did a hard reset. No joy…I thought.
>  
> I happened to sit down at my desk and catch a more extreme viewing angle of 
> the display. That’s when I realized that there was just a display issue. I 
> verified that I can start up Basic, make the system beep, open Text, etc. 
> However, I haven’t found anything that will get the display back to good 
> viewing from overhead.
>  
> BTW, I did try the contrast dial and that didn’t have any impact. The images 
> in that shared folder were taken with the contrast at its highest.
>  
> Does anyone have suggestions for debugging and fixing this?
>  
> Thanks,
>  
> george g.

Re: [M100] M100 display suddenly less visible

[George Goodman]

Thanks, Josh. My son (the family’s Electrical Engineer) is coming over this 
weekend and we’ll dive in. Your slides are very helpful!

george g.

> On 04Nov2021, at 12:27 PM, Josh Malone  wrote:
> 
> The first things to do when troubleshooting any M100 problem is to
> check that the power supply is functional. There are test points on
> the board that indicate "Vee" which is the negative 5v supply.
> 
> The slides from my TASM 2019 talk go into a lot of detail on this:
> 
> https://www.vintageboot.net/2019/09/tandy-assembly-talk-m100-repairs/
> 
> On Thu, Nov 4, 2021 at 3:19 PM George Goodman
>  wrote:
>> 
>> Hi all,
>> 
>> My M100 display seems to have taken a turn for the dim. See the images in 
>> this shared folder —> 
>> https://www.dropbox.com/sh/y1cpftct6dgqy2j/AAAEb3PmIC1b30qh7FV_WX4ea?dl=0
>> 
>> I can’t point to anything that happened. I started an install of TS-DOS from 
>> my Backpack and, once the Initial Program Load began, stepped away from my 
>> desk to get a glass of water. When I returned a few minutes later I thought 
>> the M100 had flat out died. I removed the Backpack and tried turning the 
>> M111 on and off and even did a hard reset. No joy…I thought.
>> 
>> I happened to sit down at my desk and catch a more extreme viewing angle of 
>> the display. That’s when I realized that there was just a display issue. I 
>> verified that I can start up Basic, make the system beep, open Text, etc. 
>> However, I haven’t found anything that will get the display back to good 
>> viewing from overhead.
>> 
>> BTW, I did try the contrast dial and that didn’t have any impact. The images 
>> in that shared folder were taken with the contrast at its highest.
>> 
>> Does anyone have suggestions for debugging and fixing this?
>> 
>> Thanks,
>> 
>> george g.

[M100] M100 display suddenly less visible

[George Goodman]

Hi all,

My M100 display seems to have taken a turn for the dim. See the images in this 
shared folder —> 
https://www.dropbox.com/sh/y1cpftct6dgqy2j/AAAEb3PmIC1b30qh7FV_WX4ea?dl=0 
 

I can’t point to anything that happened. I started an install of TS-DOS from my 
Backpack and, once the Initial Program Load began, stepped away from my desk to 
get a glass of water. When I returned a few minutes later I thought the M100 
had flat out died. I removed the Backpack and tried turning the M111 on and off 
and even did a hard reset. No joy…I thought.

I happened to sit down at my desk and catch a more extreme viewing angle of the 
display. That’s when I realized that there was just a display issue. I verified 
that I can start up Basic, make the system beep, open Text, etc. However, I 
haven’t found anything that will get the display back to good viewing from 
overhead.

BTW, I did try the contrast dial and that didn’t have any impact. The images in 
that shared folder were taken with the contrast at its highest.

Does anyone have suggestions for debugging and fixing this?

Thanks,

george g.