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Thread: Commodore PET 2001 RAM adapter?

  1. #161

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    Quote Originally Posted by Dubis7 View Post
    Gotcha. I've ordered a 14 Pin DIP socket and a set of new 74LS107 chips. I'll replace it once those come in and update you.
    Oh and by the way, yes a failing UD5 can produce both a black screen and probably a "stuck" UB2's output. I've finally got the connection that I wasn't seeing at first.
    So a working UD5 should give you back the video output.

    Frank IZ8DWF

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    Great. Hopefully this is our solution, then.

  3. #163

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    First remove D5 and then check that the 22 ohm is no longer there, to ground.
    Many of the clock pulse are very short duty cycle in the clock control circuits. They are not all square waves. That is normal. The signals you saw D5, pins 9 and 10 are normal. The 22 ohms on D5 pin 5 is either some fine short or D5 has failed. With D2 out of the way, it is either something along the trace or D5 has failed. If after removing D5, the short is gone, then it was D5 that failed during the rework. The entire divider circuit was working fine until the D2 rework.
    I'd still like to see an angled shot on your solder job. I don't think the soldering is the problem but I suspect the joins are poor and may cause problems in the future. When we get D5 working right, we want to make sure to leave things in good shape.
    The kind of thing that can cause such a short other than D5 is a piece of steel wool or some fine piece of other wire.
    Dwight

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    Chips came in today, as did the new sockets. My picture is back and stable!

    I went ahead and replaced the socket on D2 with something that didn't use machine pins. Your experience trumps mine, Dwight, but I have to say I had a much easier time with these more standard socket than with the machine pin sockets. These pins fit much better. That's new, as is my D5 chip (which I also socketed)

    I'm still waiting on my keys to come back from my graphics guy, but it's looking like this project may be done!

    Thanks to everyone for your help. I'll upload a picture of the final product once I have my last parts in!

  5. #165

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    Quote Originally Posted by Dubis7 View Post
    Chips came in today, as did the new sockets. My picture is back and stable!

    I went ahead and replaced the socket on D2 with something that didn't use machine pins. Your experience trumps mine, Dwight, but I have to say I had a much easier time with these more standard socket than with the machine pin sockets. These pins fit much better. That's new, as is my D5 chip (which I also socketed)

    I'm still waiting on my keys to come back from my graphics guy, but it's looking like this project may be done!

    Thanks to everyone for your help. I'll upload a picture of the final product once I have my last parts in!
    I'm glad it solved the problem.
    Regards

    Frank IZ8DWF

  6. #166

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    'enjoyed the hunt. Thanks for keeping the mind busy.
    Dwight

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