Commodore Pet 8032SK with monitor not working

[MikeS]

Hi DaveR,

Sent you a PM but maybe you missed it: I lost the address of your diagnostic ROM images, could you please repost them?

TIA,

m

[daver2]

Looks a little bit low to me. One of the fingers could be dirty perhaps? But there is at least some Volts...

Next, connect your multimeter positive lead to J3 pin 2 (+5V) and your multimeter negative lead to J3 pin 6 (cassette switch). With no keys pressed on the cassette unit your multimeter should read 0 Volts. When you press PLAY your multimeter should read 5 Volts.

J3 pin 6 gets pulled low (0V) to signal to the PET when power is required to be supplied to the motor.

EDIT: Here you go Mike https://drive.google.com/drive/mobil...13&direction=a... Enjoy!

Dave

[ilpaninaro]

Looks a little bit low to me. One of the fingers could be dirty perhaps? But there is at least some Volts...

Next, connect your multimeter positive lead to J3 pin 2 (+5V) and your multimeter negative lead to J3 pin 6 (cassette switch). With no keys pressed on the cassette unit your multimeter should read 0 Volts. When you press PLAY your multimeter should read 5 Volts.

J3 pin 6 gets pulled low (0V) to signal to the PET when power is required to be supplied to the motor.

EDIT: Here you go Mike https://drive.google.com/drive/mobil...13&direction=a... Enjoy!

Dave

Ok,
J3
pin 2 to pin 6= 0V
if i press play=4,2V

[daver2]

Excellent.

Next, multimeter positive lead to J3 pin 3 (cassette motor) and multimeter negative lead to J3 pin 1 (0V).

With no cassette keys pressed you should read 0V. With the PLAY key pressed you should read approximately +9 Volts.

Dave

[MikeS]

...EDIT: Here you go Mike https://drive.google.com/drive/mobil...13&direction=a... Enjoy!
Dave

Thanks, Dave, both for the link and also for taking the time to write it (and the doc) in the first place!
m

[Dwight Elvey]

Thanks, Dave, both for the link and also for taking the time to write it (and the doc) in the first place!
m

Dave has done what I've been saying for years, "to debug a processor requires software on that processor". There are a few things that I especially like about Dave's code for what I've seen so far. It hits most every corner of the machine. For code to be to be useful, this is needed.
Not having a Pet, ( a number of missed opportunities over the years ), it is really great to have such tools by enthusiast.
Dwight

[ilpaninaro]

Excellent.

Next, multimeter positive lead to J3 pin 3 (cassette motor) and multimeter negative lead to J3 pin 1 (0V).

With no cassette keys pressed you should read 0V. With the PLAY key pressed you should read approximately +9 Volts.

Dave

Daver2,
on J3 pin 3 to pin 1=0v
if i press Play i read always 0v

[daver2]

That’s fine. That’s what I was expecting...

Can I ask you to measure two more points with your multimeter please.

First off can you measure the voltage on both ends of the resistor R48 (15k) to 0V. You should find two readings close to 9 Volts DC. It doesn’t matter about the state of the dataset keys for this test.

Next, can you measure the voltage from UB12 pin 19 (6520) relative to 0 Volts. First with no keys pressed on the dataset and next with the PLAY key pressed. This pin should change state when the key is pressed.

If this checks out, we are probably looking at a faulty UE16 or Q1.

Dave

[ilpaninaro]

That’s fine. That’s what I was expecting...

Can I ask you to measure two more points with your multimeter please.

First off can you measure the voltage on both ends of the resistor R48 (15k) to 0V. You should find two readings close to 9 Volts DC. It doesn’t matter about the state of the dataset keys for this test.

Next, can you measure the voltage from UB12 pin 19 (6520) relative to 0 Volts. First with no keys pressed on the dataset and next with the PLAY key pressed. This pin should change state when the key is pressed.

If this checks out, we are probably looking at a faulty UE16 or Q1.

Dave

Thanks Daver!
On R48 i founded 10V in only one side!!In the other resistor side i have 0v

[daver2]

That's OK. I wanted to see that at least one side has the +9V on it...

What about the UB12 pin 19 test results? These results will affect the voltage reading on the other side of R48.

Dave