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A Tricky Commodore PET Repair: Tracking Down 6 1/2 Bad Chips

posted by janrinok on Monday April 14, @03:39PM   

owl writes:

http://www.righto.com/2025/04/commodore-pet-repair.html

In 1977, Commodore released the PET computer, a quirky home computer that combined the processor, a tiny keyboard, a cassette drive for storage, and a trapezoidal screen in a metal unit. The Commodore PET, the Apple II, and Radio Shack's TRS-80 started the home computer market with ready-to-run computers, systems that were called in retrospect the 1977 Trinity. I did much of my early programming on the PET, so when someone offered me a non-working PET a few years ago, I took it for nostalgic reasons.

You'd think that a home computer would be easy to repair, but it turned out to be a challenge. The chips in early PETs are notorious for failures and, sure enough, we found multiple bad chips. Moreover, these RAM and ROM chips were special designs that are mostly unobtainable now. In this post, I'll summarize how we repaired the system, in case it helps anyone else.

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Original Submission

• Irregardless, your explanation will helpIrregardless, your explanation will help (Score: 3, Interesting) by krishnoid on Monday April 14, @04:28PM (3 children)

  by krishnoid (1156) on Monday April 14, @04:28PM (#1400209)

  The tech-man shook his head indignantly, "They don't break down. They never break down. They were built for eternity."
  "Eternity is a long time. Just suppose-"
  "It is unscientific to suppose meaningless cases."
  "All right. Suppose I were to blast a vital part into nothingness? I suppose the machines aren't immune to nuclear forces? Suppose I fuse a vital connection, or smash a quartz D-tube?"
  "Well, then," shouted the tech-man, furiously, "you would be killed."
  "Yes, I know that," Mallow was shouting, too, "but what about the generator? Could you repair it?"
  "Sir," the tech-man howled his words, "you have had a fair return. You've had what you asked for. Now get out! I owe you nothing more!"

  Mallow bowed with a satiric respect and left.
  And two days later, the tech-man's shield went dead, and for all his puzzling and cursing never glowed again.
        -- Foundation, Isaac Asimov

  It's good to understand how things work and how they fail. I should probably get my C64 out of storage.

  Starting Score:	1		point
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  Interesting=1, Total=1
  Extra 'Interesting' Modifier		0
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• Re:Irregardless, your explanation will helpRe:Irregardless, your explanation will help (Score: 0) by Anonymous Coward on Monday April 14, @09:14PM (1 child)

  by Anonymous Coward on Monday April 14, @09:14PM (#1400236)

  Irrespective + regardless = irregardless

  Parent

  • Re:Irregardless, your explanation will help(Score: 3, Insightful) by DannyB on Tuesday April 15, @05:08PM

    by DannyB (5839) on Tuesday April 15, @05:08PM (#1400317) Journal

    Regardless or irregardless of whether gasoline is flammable or inflammable, it burns, irrespective of fire codes.

    --
    The Centauri traded Earth jump gate technology in exchange for our superior hair mousse formulas.

    Parent

• Re:Irregardless, your explanation will help(Score: 0) by Anonymous Coward on Tuesday April 15, @01:09AM

  by Anonymous Coward on Tuesday April 15, @01:09AM (#1400241)

  For a good time:
  Mallow/khallow/s

  Parent