Commodore PET 4032 no boot , no beep

[mjnurney]

So after some guess work and prodding by the vintage computer forum - thanks Dave

we nearly have a running PET.

Ive unsoldered and replaced 74SL04N UB2 i think it was and popped a new old one in.

and here we almost have a picture.

You may notice - no lines on screen.....I turned the SUB BRIGHT down on the tube , no idea why it was up or badly adjusted. perhaps it made it worse because i had the brightness up high to see the lines.

mike.
https://youtu.be/r932ah6cs80

 

[mjnurney]

http://youtu.be/MZYn0HAGLjk

Almost running now.

i get the READY prompt but no cursor - both PIAs are dead i think MOS 6520

i have it running PETTESTER with new 32K installed 4116 ram.

almost there now....

 

[sir_beaker]

Good job

Great to see it being resurrected

 

[roy_bates]

sorry mike i missed this thread....


field coil dont look moved it looks flush with the tube and the picture looks square.(apart from the milk bottle effect at the bottom half of the picture)
if you have to do anything with the transistors,change the thermal paste mate on them all,they will just burn out as they dry up and paste becomes useless.

you may of seen me comment of thermal paste on old monitors in some of my own threads,its worth doing and on power supply's.

great job mate

 

[mjnurney]

hi guys

the screen needs some attention , i will strip the board out and have a good look. It always crackles when the power is applied until the crt controller kicks in and it displays a picture.

it sounds like the fly back crackle...

i need to measure everything and check the caps.

 

[mjnurney]

The plug in ram and rom board has arrived and now i have a working PET. If i select system rom and ram - it will not boot but lower ram is working fine giving 16k of free ram but the rom selection stopes the pet dead. So i have a ROM or rom related problem still to fix.


however if i select just the ram/rom board settings and ignore the PET ram & rom it boots just fine.

mike.

http://youtu.be/GAfVCoTNM98