CBM PET 3032 STRANGE BOOT

[daver2]

It looks like you have a number of unrelated faults...

Let's go back a bit with the history of this PET... What did you repair in it originally?

Dave

 

[Desperado]

I'm desperate now because I don't remember what problem this computer had...we fixed many of them

Time to nop??

 

[Desperado]

I founded! This is original post:

https://forum.vcfed.org/index.php?threads/not-working-cbm-3032.1241085/

 

[Desperado]

I have low signal on ud9 pin 20

 

[daver2]

Under what conditions? This might be normal...

Cause and effect...

Dave

 

[Desperado]

Under what conditions? This might be normal...

Cause and effect...

Dave

With pettester inserted Dave...now i have always scrambled chars screen when i turn on...maybe there was a component that has definitely failed now..
Time to Nop gen?

 

[daver2]

Nop away!

Dave

 

[Desperado]

I inserted Nop and i checked output signals on C3 and B3..i have correct waveform signals.

 

[Desperado]

Now D2 pins 1 to 17, right?

 

[daver2]

Correct.

Don't forget to check pin 20 on the ROMs / ROM sockets at the same time.

Did you also check the buffered address lines from B3 and C3 on the pins of the ROMs / ROM sockets at the same time?

Dave

 

[Desperado]

Don't forget to check pin 20 on the ROMs / ROM sockets at the same time

I have signal on every rom pin 20 and on UD2 pin 1 to 17 !

 

[Desperado]

Did you also check the buffered address lines from B3 and C3 on the pins of the ROMs / ROM sockets at the same time?

Yes i have also these signals Dave

 

[daver2]

Have you checked the ROM checksums are correct?

I am guessing they will be, but it would still be wise to check at this point.

Dave

 

[Desperado]

Have you checked the ROM checksums are correct?

I am guessing they will be, but it would still be wise to check at this point.

Dave

yes ud8 and ud9 are correct!

 

[daver2]

Is this the machine that had the socketted buffers at E9 and E10?

Dave

 

[Desperado]

Is this the machine that had the socketted buffers at E9 and E10?

Dave

Unfortunately not.... Are solded on board

 

[daver2]

Ok, so the next step is to look for data bus contention. But, remember, you can't use the data bus pins of the CPU with the NOP generator in place. You have to use (say) the data bus pins of a ROM (such as the EDIT ROM / PETTESTER ROM).

Dave

 

[Desperado]

Ok, so the next step is to look for data bus contention. But, remember, you can't use the data bus pins of the CPU with the NOP generator in place. You have to use (say) the data bus pins of a ROM (such as the EDIT ROM / PETTESTER ROM).

Dave

Ok Dave, these pins on every Roms?

 

[daver2]

Yep.

Look for any voltages in the range 1.0V to 4.0V.

Dave

 

[Desperado]

Good morning!
I have this waveform signal on every rom ics (pins 0 to 17 except pin 12).