Restoration Project - Commodore Educator PET-64

[RickR]

As noted in the "pickups" thread, I recently lucked into purchasing a very rare computer, the Commodore PET-64.  I'm going to use this thread to document the process and progress in restoring this computer.

GOALS: 

• Make the computer fully functional and enjoy playing some C64 games on it. 
• Make it presentable for permanent display on a desk in my gaming room.
• Do no harm!  If I can't fix it without destroying it, leave it alone.

Current State:

• It is extremely dirty on the outside.
• The computer does power on!  The keyboard and screen work!  However, the computer freezes after about 30 seconds. 
• No idea on the condition of the SID chip.
• The "5" key on the keyboard has broken off (the stem is broken).  I have the key with stem still attached.

Here it is in the initial state:

 

[RickR]

I think this video will be useful, even though it's not the exact model I have:

 

[RickR]

Here are some pics of the outside cleaned up.  I used a bucket of dish-soap water and a washcloth and it seemed to work very well.  Not perfect, but better than before.  The keyboard got vacuumed and that helped tremendously. 

 

[RickR]

And using the 8-bit Guy video above, I was able to figure out how to open the case.  It flips open like a car bonnet!  Not mentioned in his video -- there are two screws on the side that have to come out before it will flip.  Easy enough.  The inside is very dirty.  There is some hair and a thick layer of dust covering everything.  Next step is to vacuum and spray with compressed air, but I think it's going to take more soapy water and washcloth action to get the dust off.

 

[RobertLM78]

Looking forward to seeing how this turns out 😎

[RickR]

Here are a few before/after shots of the interior cleaning.  It was dirty to the point of being gross.  This dust would not blow off, it needed to be scrubbed off.  I did it gently, with water and dishsoap applied with a washcloth and soft toothbrush.

 

 

 

 

Edited December 8, 2023 by RickR

[RickR]

And after a day of drying time, I fired it up.  Still the same.  It works, but freezes up after about 30 seconds.  I'm glad I didn't break it at least.

Next steps are some diagnosis steps.  Start with the power adapter and the voltage regulators. 

[- Ω -]

Question @RickR, have you been able to do anything like run a simple two line program with the 30 seconds?  Have you been able to access the disk drive?  Can you post a small video of what happens?  How long is the recovery time after lockup until you can get another 30 seconds out of it.  Is the time exact on the lockup every time?

[- Ω -]

19 minutes ago, RickR said:

And after a day of drying time, I fired it up.  Still the same.  It works, but freezes up after about 30 seconds.  I'm glad I didn't break it at least.

Next steps are some diagnosis steps.  Start with the power adapter and the voltage regulators. 

What kind of diagnostic tools do you have?

[RickR]

1 minute ago, - Ω - said:

What kind of diagnostic tools do you have?

A voltmeter and an EE degree 🙂 

3 minutes ago, - Ω - said:

Question @RickR, have you been able to do anything like run a simple two line program with the 30 seconds?  Have you been able to access the disk drive?  Can you post a small video of what happens?  How long is the recovery time after lockup until you can get another 30 seconds out of it.  Is the time exact on the lockup every time?

No, there isn't enough time to type even a simple program, as the keyboard is pretty stiff and slow. 

I haven't timed it, it is approx 30 seconds, but probably less.  Turning the computer off, then on again gets another 30 seconds.  The computer simply freezes. 

 

[Marco1019]

On 12/1/2023 at 2:47 PM, RobertLM78 said:

Looking forward to seeing how this turns out 😎

Indeed, this looks like quite the project. Thanks for sharing, @RickR!

[- Ω -]

9 hours ago, RickR said:

A voltmeter and an EE degree 🙂 

No, there isn't enough time to type even a simple program, as the keyboard is pretty stiff and slow. 

I haven't timed it, it is approx 30 seconds, but probably less.  Turning the computer off, then on again gets another 30 seconds.  The computer simply freezes. 

 

Well if you can turn it off and immediately back on, it's not a thermal issue.  It's the timing that interests me, could it be locking up when trying to access the disk drive?

[RickR]

I think you are right on the thermal part.  There is not disk drive connected, and Commodore computers don't auto connect to anything. 

On real C64's, the power supplies go bad because they filled them with resin.  Some components would overheat because of that, causing overvolt situations.  Well the good news with this model is that the power supply has no resin.  I will check those voltages, but I'd guess it is not that.

It can't be the fuse, as the computer would shut down if that was failing due to heat. 

It may be a bad chip.  SID chip perhaps? 

I have the day off work tomorrow, and I may spend an hour or so with this project. 

 

 

[RobertLM78]

17 hours ago, RickR said:

And after a day of drying time, I fired it up.  Still the same.  It works, but freezes up after about 30 seconds.  I'm glad I didn't break it at least.

Next steps are some diagnosis steps.  Start with the power adapter and the voltage regulators. 

Hey, the same behavior after the cleaning is a good thing... 🙂 

[RickR]

OK, I spent about an hour with it yesterday and I made a tiny bit of progress.  First step was identifying all of the chips, which I did.  The biggest shock was that it has no SID!  Although there is a spot to solder one in.  This fact really dented my enthusiasm for this project.  What good is a C64 with no SID chip??? 

Anyway, I'm almost 90% sure that it's the power supply that is bad.  The bad part is that it isn't a standard connector, so I can't try a standard C64 adapter.  I'll do a little more research here and get better test measurements from this supply after 30 seconds.

But given the lack of SID, I think I may start looking for a local buyer.  This computer is rare, and the board without SID makes it even more rare. 

[RickR]

Just a quick update:  I found a local expert to help me diagnose and fix the computer.  In the end, I decided to sell it to him with the promise that he's going to fix it and keep it.  My buyer completely understands and appreciates what this machine is, so I'm happy with my decision.   He's going to keep me in the loop for updates and I'll post those here as I get them. 

His initial assessment was to look for any cracked solder joints, as those can be impacted by heat and explain the 30 second freeze I saw.