I typed same text in all lines.
Thanks. Out beyond my skis here but learning and having some fun. I'll
probably fry the thing trying to fix it.
On Sunday, July 26, 2020, 05:05:36 PM EDT, Ken Pettit <petti...@gmail.com>
wrote:
Hey Chris,
The LCD has 10 actual controller chips. Each one controls 4 lines x 50
pixels. The two completely blank areas on the screen are the exact size of one
of the controllers. It looks like either those controllers are not
functioning, or the enable signal driving them is not functioning (bad decoder
IC, bad trace, bad connector). I can't tell if the others have missing single
pixel columns, or if the text is actually missing some letters (i.e. should
line 6 actually say "test of the TRS-80" or does it really have spaces instead
of text there?
Ken
On 7/26/20 12:54 PM, Chris Fezzler wrote:
No after market ROM.
Logically, I would think the fact that the top four lines are perfect, the
hard reset produces a perfect Menu screen, and just the bottom four lines are
garbled would be a clue where to look.
I know nothing other than reading a lot off Internet. My instinct tells me
the issue is a component that regulates power or signals to the LCD driver
chips for the bottom half of the screen. The are getting power (because we see
gibberish and the perfect Menu screen) but perhaps it is the wrong voltage or
intermittent power or signal.
Thoughts are:
Capacitors C47 or C54 and or M17 and/or M25.
But I don't know how to determine their impact on the issue.
On Sunday, July 26, 2020, 11:25:01 AM EDT, Jeffrey Birt
<bir...@soigeneris.com> wrote:
When comparing your two pictures, after rotating them right side up, I noticed
just now that not only do you have blank blocks but some of the characters are
reversed. That is really bizarre. I’m not sure if that points to a problem
with how the LCD drivers are being configured/initialized or what data is being
sent to them.
If the driver ships are outputting a built-in font here it might be a chip
configuration issue. If the display is always bit mapped, then it would be
something else.
Do you have any sort of aftermarket ROM installed?
Very interesting problem.
Jeff Birt
From: M100 <m100-boun...@lists.bitchin100.com> On Behalf Of Chris Fezzler
Sent: Sunday, July 26, 2020 9:47 AM
To: m...@bitchin100.com
Subject: Re: [M100] Listserv Search
Gladly.
On Sunday, July 26, 2020, 08:36:06 AM EDT, Jeffrey Birt <bir...@soigeneris.com>
wrote:
Can you attach a picture of the cold boot screen too?
The positive and negative clips go to a +5 and ground source on the M100 PCB
itself. The PPS setting if ‘Pulses Per Second’ when using it as a logic pulser,
i.e. to inject a pulsing signal. On the chip select lines you should she them
quickly toggling.
Jeff Birt
From: M100 <m100-boun...@lists.bitchin100.com> On Behalf Of Chris Fezzler
Sent: Saturday, July 25, 2020 6:20 PM
To: m...@bitchin100.com
Subject: Re: [M100] Listserv Search
ALERT: Beginner asking question.
Reminder: Upon hard reset the LCD initializes perfectly and displays the main
Menu screen perfectly. However, once in BASIC or TEXT the bottom four lines do
not display correctly. (See attached.)
(Planned to test LCD in M102 but it has a different connector. I don't have a
second M100 right now to test it in, but I am 99.99% positive the LCD is fine)
So I purchased a logic prob (Elenco LP-900) to test chip select lines on the
LCD connector (Pins 14, 12, 10, 8, 7, 16,15,13,11, 9, and CS1=Pin? - schematics
blurry).
As I unboxed it I remembered I never used one before. :)
- Where do I place the pos and neg alligator clips?
- Do I set the logic prob to 400PPS or 00.5PPS?
- In checking the chip select lines, am I looking for HI, LO, or PULSE?
I see no broken or corroded lines on the board.
Thanks in advance.
On Wednesday, July 22, 2020, 02:29:39 PM EDT, Jeffrey Birt
<bir...@soigeneris.com> wrote:
This loss of an entire block is the symptom of a missing chip select. When the
LCD driver chips are powered/reset they will drive every pixel on/black. When
they receive the proper initialization, they will drive every pixel off/clear.
It seems the rest and initialization steps are being done so commands are
getting through (and the machine is booting so the LCD has to be initializing
and responding).
Each driver chip on the LCD controls one block of pixels. If an entire block is
missing, it is a good sign the chip select is not getting through. It could be
a bad trace on the M100, a bad LCD cable or a bad LCD itself. If you have a
scope of logic probe you can check to see if all the chip select lines are
toggling.
Jeff BIrt
From: M100 <m100-boun...@lists.bitchin100.com> On Behalf Of Chris Fezzler
Sent: Wednesday, July 22, 2020 11:26 AM
To: m...@bitchin100.com
Subject: Re: [M100] Listserv Search
Here you go.
On Wednesday, July 22, 2020, 11:52:23 AM EDT, Stephen Adolph
<twospru...@gmail.com> wrote:
a pic of the garbled screen would be great if you can do it.. thanks
On Wed, Jul 22, 2020 at 11:37 AM Chris Fezzler <fezz...@yahoo.com> wrote:
Sorry - typing too fast. Top four lines of the screen.
Yes, mostly garbage all of the time. Except a hard rest will generate a proper
menu screen.
Yes, in BASIC the same. But if I type in a test program and hit RUN the
program will indeed run.
So the computer is getting the commands/keystrokes. Just not displaying bottom
four lines.
I think it is a component issue.
On Wednesday, July 22, 2020, 09:20:53 AM EDT, Stephen Adolph
<twospru...@gmail.com> wrote:
Hi Chris,
What do you mean by "the top 4". Do you mean top 4 lines on the screen? I
think so.
So is it correct to say that the LCD bottom 4 lines display garbage at certain
times
* not after a (hard) reset - you get a correct MENU display (not just a RESET
but a HARD RESET?)
* when you enter BASIC and/or run any software, the LCD bottom half shows
garbage?
I would suggest that you run a memory test.
I doubt that you have a fundamental problem with the LCD system, nor the
keyboard system.
good problem!
On Wed, Jul 22, 2020 at 9:02 AM Chris Fezzler <fezz...@yahoo.com> wrote:
I'm trying to troubleshoot what components on the circuit board process
keystrokes and send them to the screen.
The screen and keyboard on my Model 100 are in perfect working order. But only
the top four are processing correctly.
The bottom four are displaying gibberish. But if I type commands in BASIC,
they work. So again, not the keyboard or
screen but components that process the bottom half. A hard rest will present a
perfect menu screen. But upon entering
an app, the bottom four lines are not getting proper signal.
Sorry, I'm not an electronics or computer engineer. Just a hobbyist with a
soldering iron and a willingness to learn.
Plan to look at Technical Reference Manual to see if I can troubleshoot.
On Wednesday, July 22, 2020, 01:15:25 AM EDT, John R. Hogerhuis
<jho...@pobox.com> wrote:
On Tue, Jul 21, 2020 at 5:08 PM Chris Fezzler <fezz...@yahoo.com> wrote:
Is there a way to search old Listserv messages so I can research before
embarrass...err...I mean ask a dumb question.
Seriously, would like to research.
How old are we talking?
Gmane was our archive until it went down for a long time. Then it was back up
recently but only accessible through nntp readers. Not sure the status of that.
Our GNU Mailman list itself has an archive which goes back to 2011 when I took
over running the list.
http://lists.bitchin100.com/private.cgi/m100-bitchin100.com/
Or just ask. We Are The Archive.
-- John.
