Re: CBM 3032 (PET 2001N-32), no video?

Den Sat, 24 Feb 2018 14:19:23 -0800 skrev Valerio Castelli
<v.castelli92@gmail.com>:
> Just checked the voltage on the winding for the monitor supply, it
> shows 16.5 Vac, which is a little lower than the 18Vac you mentioned.
> Is that within tolerance? Otherwise I’ll have to check the monitor
> PCB, it may indeed be a cracked solder joint… It’s my first
> experience with a CBM, but other computers of that era tend to have
> this kind of issues as well, I guess it’s rather common.

I'd check the signals from the main logic board up to the monitor. An
oscilloscope is ideal but a simple volt meter could be usable. If you
don't have anything to measure with you could use a series resistor and
the input of some crap audio amplifier/speaker setup. You should hear a
rattling sound on VSYNC and with really good ears might hear something
on HSYNC but probably not. Video out should give a rattling sound if
there is something on screen. If you hear that (or see something on an
oscilloscope) you could try pushing SHIFT + CLR/HOME and see if the
signal almost goes away. If so you probably had a correct startup
screen and just cleared the screen.

If you want to see if the CPU starts, you could connect a datasette and
see if the motor turns on and off as you press play/req/fwd and stop.
(If the datasette seems to work but you are unsure if the motor really
stops in stop mode, you can open the lid and feel if the capstan axle
turns even in stop mode. That is an indicator of that the CPU doesn't
run the correct code from ROM).


-- 
(\_/) Copy the bunny to your mails to help
(O.o) him achieve world domination.
(> <) Come join the dark side.
/_|_\ We have cookies.

       Message was sent through the cbm-hackers mailing list