PET 2001 16 N Mystery

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Thu Jul 31 15:51:00 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

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
Received on Thu Jul 31 2003 - 15:51:00 BST