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Hi, new to the forum, fixing a Commodore PET

Bad IC sockets are one of the most common PET problems, along with bad ROM and RAM chips; more so on the older models, but of course any contact can be deformed or oxidized. I treat all mine with Stabilant 22 FWIW.

Great to see that you're finally almost there; it's been an interesting trip to be sure.
 
.. paranoia ..

Took me about 1 hour and more to replace the socket ..

1 track broke and 3 pads lightly cracked but I managed to restore all with a tiny bit of wrap wire.

I want to check all connections one by one before to put the 6520 in and see how it goes.

Now there's a brand new tulip socket in.
 
MikeS said:
Fingers crossed...
Click to expand...

Ok .. 'as before' .. it boots and all but it looks like one ( or at most 2 ) rows of the KB are not working.

Looking for a KB diagram to check what they could be.

[edit] - Found it, after a check it seems that all works but 'ROW3' ( D3 I think ) now checking all is connected where it should/etc, the keys also 'a' and
''left shift" seems to have a bit of a dirt problem, all other keys are working.
 
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.. and finally ..

FinallyPet.jpg


Ok reassuming :

- one of the 2114 was not very well
- the 7425 was definitely broken
- the roms that looked ok actually using an FC ( fc /b file1 file2 ) seems to show a few differences compared to the downloaded ones, currently running with the contents of dowloaded roms
- 'D3' of the keyboard column was actually not making a good contact and the spring broke almost immediately as I tried to gently push back to take it out
- 'A' and right shift must have a bit of dirt/oxidation problem ( they work if you stroke them a few times )
- question mark on the VIA ( 6522 ) chip for now but suspect the original one had some trouble
- question mark on the second PIA for now
- definitely the old 40 pin sockets seems to be not well holding
- probably the same on the ROM sockets as well ( but with my new stuff does not matter much now )

If you flex and push the PCB a bit and/or you squeeze a bit "around the area of the via" you may have problems at startup, I think ( but not today ) I'll be going to replace the VIA socket too I definitely think the springs simply are not any more up to the job.

Wonder if some old soldering or such but after much looking around the whole PCB seems well soldered.

But I really believe the VIA socket needs to be replaced as well, probably the other PIA socket too.
 
Well done!! GilesGoat hope when my 74153 mux arrives I can make a bit more progress on my pet!

You're pet sounds just as stubborn as mine, everytime you find a fault another one needs attention.
 
We are still a bit far away from total functional.

I believe I'll probably have to replace the remaining 2 40 pin sockets to have the cassette working as well.

Then I have to add a reset button ( to avoid swtiching it on and off ) and make on more smaller adapter for the remaining ROMS and try to burn Basic 4.0 on them.

Ah and what's that 'add on' to give it an 'audio output' too ?

Finally in the future I'll have to locate ( already know some place to look for ) some 4116 chips, we have to put that machine back to the 32K it was supposed to have ;)

[edit] - after changing the 40 pin socket of the VIA it seems it does not do any more the 'wobbly chip' thing.

After cleaning all the keyboard including the matrix now 'a' and 'shift' are back to work.

Finally we tried the tape and it seems it's capable to load programs ( we have to try with SAVE now )

So my next first thing has to be a reset button.
 
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