Subject: PET 2001 16 N Mystery

From: [email-masked], "Co." <[email-masked]>
Date: Wed Jul 30 22:05:30 2003

I wish to pose this question with the hope that there is someone 
else who has had the same thing happen to them, and/or can suggest 
a cause/fix..

I have a Commodore PET 2001 16 N.  Whenever I try to write or read 
from tape (using 1530 drive) the computer freezes up and I am forced 
to turn off/on.  After powering the unit back on, the screen is filled 
with garbled characters.  Turing off/on does not fix.  However if 
I wait a day or two later the computer is OK and the garbled characters 
no longer appear.  I have reproduced this series of events twice 
and again the computer "fixes itself." I do not want to try again 
for fear of permanently ruining the machine.  Any ideas about what 
causes this?  Anyone had this happen to them?

---

From: [email-masked] (Tony Duell)
Date: Thu Jul 31 21:19:58 2003

> to turn off/on.  After powering the unit back on, the screen is filled 

This sounds like a power supply problem -- the extra load of the tape 
drive motor is pulling the unregulated supply down, which is then 
causeing the 5V line to drop too low.

Many PETs have a white Molex 0.156" power connector on the mainboard, the 
socket part of which is wired to the transformer and smoothing capacitors 
mounted seprately in the case. This connector is somewhat under-rated, 
and tends to go high resistance and overheat. If the plastic has started 
to turn brown, this is one of your problems.

Either replace the connector, or remove it completely and solder the 
wires directly to the main PCB (you might then want to add an in-line 
connector of a suitable rating to aid future servicing).

Also, check the smoothing capacitors (particularly the large ones mounted 
off the main PCB). It's possible one of those has dried up.

-tony