Re: Will pay good money for NON working PET 2001 motherboard.

-------- Original-Nachricht --------
> Datum: Sat, 07 Nov 2009 22:59:33 +0900
> Von: Philip Lord <random6000@mac.com>
> An: cbm-hackers@musoftware.de
> Betreff: Re: Will pay good money for NON working PET 2001 motherboard.

> First thing I noticed was that there were many keys not working or  
> working sporadically, however I was still able to quickly write a  
> 'hello world' program to confirm that the basic was function  
> correctly. All seemed good until I tried to load a tape. After typing  
> 'LOAD' and pressing return the computer would freeze. I would not get  
> the 'press play now' message, and the tape drive would no longer  
> function. Turning the machine off and on again brought the machine  
> back to life, and the tape drive was able to move again through FF,  
> REW and PLAY buttons. Typing LOAD or SAVE would lock everything up  
> again.

The keyboard could be bad keys, but also the keyboard PIA going bad.

The tape is connected to the keyboard PIA and the VIA. If the machine
locks up when accessing the tape, it could be one of those.

> 'Commodore Basic' greeting screen was not displaying either, just the  
> flashing cursor.

Is the cursor flashing with the normal speed or faster?

PIA1 (keyboard PIA) also creates the system interrupt. The system
interrupt controls cursor speed. I don't actually know how an "always on"
or "always off" cursor would look like.
You could check the IRQ line if it is always on or always off.

> Anyway, I'm guessing that maybe the character generator ROM has died???

Don't think so. You'd have garbled characters, but would be able to
use the machine as before.

I'd check the PIAs, for example by swapping them, or replacing them with
known good parts. Same for the VIA. 
If they are in sockets, reseating them may already help if you haven't
done so.

André


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