Repairing Old Stuff: Commodore PET 2001 – 8 (1977) – Part 1

I have salvaged this lovely Commodore PET 2001 – 8 (Earliest time code on ICs is 1978 so far) from eternal storage and inevitable decay.

I hope to restore the PET to a reliable condition by cleaning the board connectors etc, replacing capacitors where feasible and reseating all of the accessible chips. Some may even need replacing but I will cross that horrendous bridge when I come to it. I have very little experience with this but the PET is in ok nick after being in an engineering lab for 35 years. So as a warning, do not take this as a tutorial.

I would love some advice, so if you can share some techniques I would be very grateful. If you have any memories of 1970’s computing or have similar old tech then please let everyone know.

7 comments for “Repairing Old Stuff: Commodore PET 2001 – 8 (1977) – Part 1

  1. Willi Kusche
    July 12, 2015 at 21:01

    I have a PET 2001 that has a CGRS EXS100 connected to it. In the S-100 slots made active by the EXS100 are a 32K RAM card populated with 24K of RAM and a Versafloppy controller card driving two eight inch floppy drives. I used this system in the 80’s as a software development system. After the system sitting idle for about 25 years I’m trying to get it running again. It does boot but only one of the keys work so I’m looking for tips on how to make the chiclet keys working again. I also have another PET 2001 with the chiclet keyboard but that one is showing absolutely no sign of life.

    • David Watts
      July 12, 2015 at 21:26

      Hi Mate,

      My keys were also a bit dodgy, I had to take the keyboard apart and clean the contact with some isopropyl alcohol. Works fine now although the chiclet keys were never really great to type on.

      • Willi Kusche
        July 14, 2015 at 02:50


        I was re-installing the keyboard after a second attempt at cleaning it when I finally noticed that some of the wires, of the cable that runs to the motherboard, had broken off at the keyboard end. Fortunately, that was the second keyboard that I decided to practice on. I have a vague memory of the connector at the motherboard end snagging on something when I was moving it. I’m now taking the precaution of taping the motherboard end of the cable to the bottom of the keyboard when moving the keyboard about.

        • David Watts
          July 14, 2015 at 12:44

          I am glad you found out what the problem was, I hope you will be up and running soon. The next thing I would love to do with the PET is to redesign the power supply. It eats up a lot of power so I think a switching supply would make more sense, but it will also add noise to the system. I also don’t know how many different voltages it currently kicks out, I have a fair bit of research to do.

          • Willi Kusche
            July 17, 2015 at 03:26

            The “-“, “3”, “6” and “9” keys seemed to be dead so I was concerned that a wire was broken. An unnecessary worry as another keyboard dis-assembly, cleaning and re-assembly cycle cleared that problem. Still have some keys that require heavy pressure to work. The RAM on the S-100 RAM card still isn’t recognized so I’m temporarily giving up on the EXS100 adapter and will give the BETSI S-100 adapter a try.. The PET needs 5 and 12 volts but why worry about the power it uses if you’re only going to turn it on only once in a while?

  2. Peter Lamont
    October 22, 2014 at 06:30

    Hi i just wanted to congradulate you on being a lucky lucky sob. That is one of the first pcs ever built. The blue label indicates it was built circa 1977 or very early 78. It is extremely rare. I have a pet 2001-8 circa 1978 with the black label. Take care to ground yourself as the chips from this era are extremely static sensitive. I burned out 2 uart mos chips without any effort at all. The uart on the 2001 is the 6520 and ive only ever found 3. I bought all 3. The rom you have is also not the original but an upgrade demanded by commodore due to the bugs and extreme limitations of the original. The only way to tell the difference is the number signs surroundi g the basic announcement message. The original uses asterisks. Your commodore can have more than 32k ram if it uses bank switching. All rammay not be addressable at once ut can contain many bank switched banks. The commodore b for instance could only address 64k but had 256k! 6502 monitor o this machine is accessable and id love to collaborate on some stuff if you wish! I also have some info on the rom architecture

    • Richard De
      May 11, 2015 at 13:49

      Hi, also have a 1977 Pet serial # 32901 with 24 Cursor Magazine Tapes and was wondering if you know anyone interested in buying ? I also have a KIM 1,both have all a lot of literature on them…

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