Commodore.ca: The PET, VIC, 128, 64 & More Forum

I have a PET 2001-32B upgraded to BASIC 4.0. Cassette Port 1 on the back doesn’t fully work. It detects when play is pressed and the Datasette turns, but it stays on “searching.” Cassette port 2 inside usually works fine, although it usually won’t find a file unless I load the exact file name without * wildcards. (I’m new to PET so I don’t know if this is normal behavior.) This behavior is the same with a physical Datasette and with the 1541-Ultimate tape adapter receiving TAP files served from a Commodore 64.

Using the internal port has been a fine workaround. However, I just got a Cassiopei 2.0. Apparently the Cassiopei uses BOTH cassette buffers, and as a result I can’t use it fully. I can use it in single file loading mode in port 2, but I can’t use its custom Menu loading program. So I need to fix my PET.

I’ve thoroughly cleaned the port 1 contacts. It behaves the same regardless of the cassette device used so I’m confident the problem is internal to the PET.

Can anyone point me in the right direction? Is there a particular chip which would make cassette port 1 go bad while not affecting cassette port 2? Or, is there a single chip that controls both cassette ports which might be on its way out?

Is there a source for such chips?

I really want to get this working because the machine is in beautiful condition otherwise and I’m eager to get it working fully.

Hi,

The cassette ports are handled by different chips, that could explain the symptoms.
The read line of cassette port#1 (marked as "J3" on the mainboard) is connected directly
(without any level conversion) to the 6522 VIA IC, while the read line of cassette port#2
(marked as "J6") is wired to the 6520 PIA directly.
These ICs are the closest to their respective tape port, the VIA IC is smaller compared to PIA.
Since there's no protection on these IC inputs, they are vulnerable to electrostatic discharge.