I am able to blindly go into Basic and type "beep" and it beeps. I even make
a program:
10 beep20 goto 10run
and it beeps over and over until I break.
Since I am able to do this, wouldn't this mean that my RAM is OK?
Thanks,Chad
On Monday, August 19, 2019, 09:07:57 PM CDT, Jeffrey Birt
<bir...@soigeneris.com> wrote:
No display can also be a symptom of failure to completely boot up due to bad
RAM. Ask me how I know 😊
The first M100 I got had similar symptoms and I had to resort to putting a
logic analyzer on the data lines and recording the boot process and comparing
that to a commented disassembly of the ROM I found online. When it got to the
point of copying some ROM code to RAM (some snippet that runs from RAM in
normal operation) it was overwriting the stack. I had to swap out the soldered
on 8K RAM module for one of the option RAMs.
Jeff Birt (Hey Birt!)
From: M100 <m100-boun...@lists.bitchin100.com> On Behalf Of
chadhendrick...@sbcglobal.net
Sent: Monday, August 19, 2019 8:35 PM
To: m100@lists.bitchin100.com
Subject: [M100] M100 display not working, all else seems good
Hello,
New to the list. Just pulled my Model 100 out of storage where it had been for
at least 20 years.
It would not power up so I have replaced many of the electrolytic capacitors
(several of which were obviously leaking) including all the ones near the power
switch (C83, C82, C85, C84, C90, C86, C92) and also four 10uF caps over nearer
the modem switches (C49, C50, C54, C55).
It will now power up but there is no display.
I know it is powering up because I am able to blindly go into Basic and type
"beep" and the speaker beeps. This also proves the keyboard is working.
I am powering with four fresh AA batteries.
I've tried adjusting the contrast knob. I've tested the NiCD battery and it is
showing 4.4v.
I've tested VDD (+5v), VB (+5v), and VEE (-5V) and all test solidly good.
Ribbon cable has been reseated and looks good.
When I do a Reset, I can hear a slight click from the speaker so that button is
working. I have tried doing a cold reset (control-shift-break-reset) and still
no display.
When I power off, the battery LED flickers quickly so that is working.
What would be my next steps? Is there a good place on the LCD to test to make
sure it is getting good power? If so, where?
Thanks in advance,
Chad
