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Thread: Curious 2001N fault

  1. #1

    Default Curious 2001N fault

    Hi all,
    I've just received a 2001N (32k, Basic4) PCB to repair. The owner said it was working for few seconds, then the cursor disappeared and after that, it just displayed the usual garbage screen.
    Within the first inspection I've found a 4116 chip split in half. This board has all ceramic 4116s, the kind of "eprom" package with the two halves epoxied in the middle. Now, the owner told me he didn't hear any "pop" or other sound and I guess a splitting chip would make some noise.
    I do really hope it was a "transport" problem, even if the board was packaged in a more than adequate box.
    An electric problem that splits a 4116 chip would never forgive all the others I think.
    Did anybody ever see something similar?
    When I was a kid I did "split" some transistors by applying the AC line voltage to them (unintentionally most of the times) and it's quite a powerful even that can't go unnoticed.
    Diodes on the power supply look good, and I asked the owner to measure the secondary voltages on the power transformer (all ok). I'll substitute all tantalums before even dreaming about powering on this one.
    Another thing to do would be measure the regulators output, but it's difficult to do that without powering all the rest :/

    Frank

  2. #2

  3. #3
    Join Date
    Jun 2012
    Location
    UK - Worcester
    Posts
    2,687

    Default

    This looks to be a mechanical/bonding (or lack of bonding) issue as opposed to electrical.

    If it had been electrical, the silicon woul dbe in a messed up state !

    Dave

  4. #4

    Default

    Quote Originally Posted by daver2 View Post
    This looks to be a mechanical/bonding (or lack of bonding) issue as opposed to electrical.

    If it had been electrical, the silicon woul dbe in a messed up state !

    Dave
    Yes I agree, I thought about that later. The chip was probably cracked and the first thermal expansion, split the case in half. Replacing that chip resulted in a fully functional PET.

    Frank

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