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Repair method

Discussion in 'Electronic Repair' started by russ lavergne, Jan 25, 2006.

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  1. I am working on a little board that is part of a big coin op redemption
    piece. It has 5 IC's 12 TIP22 transistors a bunch of caps on the IC's.
    another transistor and two other electrolytic. There are five of these
    boards. All exact duplicates. So I thought that this would be a good time
    for a Huntron. But no matter what I do I can't seem to isolate the problem.
    It seems where ever the fault is it influences the whole board. Is there a
    technique or tool I can use to figure out where the problem is? I can't
    apply power because it needs the whole setup to run and it is far away in a
    crowed busy place. Any helpful ideas out there for me.
  2. Arfa Daily

    Arfa Daily Guest

    Might be helpful to know what the problem is. I repair some boards for a
    commercial operation, that has machines that use them all over the place. In
    theory, these need the rest of the machine as well, but by providing these
    boards with power on the bench, and then simulating the inputs with
    switches, the CPU clock and strobe signals with a couple of 555 timers and
    the output loads with power resistors with LEDs across them, I am able to
    carry out full diagnostic checks on every aspect of the board's operation,
    and repair them with absolute confidence. Might be possible to do the same -
    especially if you are likely to have to do more ??

  3. The first step to any effective troubleshooting is to understand the
    function of the circuit. Without that info you can't really do very much.
    Next you have to understand the individual components and their relation to
    the function of the circuit. What does the board do? What are its inputs
    and outputs? What components are these ICs and transistors that you listed?

  4. Lynn Coffelt

    Lynn Coffelt Guest

    Here's a thought...... maybe only practical if the IC's are
    through-hole (not surface mount).
    I was faced with a similar problem which involved a car wash facility
    with about a dozen exact duplicate PCB's (and one spare!). Instead of trying
    to reinvent the entire operation (no schematics or manuals, of course), I
    noted that new IC's were available for about $.30 each, and the transistors
    were even less. Just change them all! Didn't take much more time than first
    troubleshooting and then repairing (which involved replacing something
    Dumb, stupid and lazy? You bet! But, hey.... I could get the car wash
    up and running pretty darn quick.
    Old Chief Lynn
  5. James Sweet

    James Sweet Guest

    What's wrong with the boards? A DMM with a diode check function is
    probably the best tool for the job, just test all the transistors,
    they're the most likely fault in a machine like that which drives motors
    or lamps.
  6. Von Heler

    Von Heler Guest


    "Receive to it the right in top you, kissing you the stupid
    hun and kiss
    your team like well." - Glasweigan
    "we are total pricks!" - ZB
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    We're in Europe and you're no.

    I'm LOVIN' it.
  8. DaveM

    DaveM Guest

    In this scenario, your best approach might be to get a known good board and
    record (sketch) the Huntron waveforms on each of the ICs and transistors.
    Then you can compare the waveforms on the bad boards to the good one and
    come up with a likely bad component.

    Another approach could be to try to reverse engineer the circuit and draw a
    schematic. That would certainly help you to analyze the problems. The
    circuit schematic would also allow you to design and build a test setup that
    would simulate normal inputs and allow you to analyze the outputs.

    What kind of ICs are on the boards? Download datasheets from the internet
    to help you determine what's working and what isn't.

    Dave M
    MasonDG44 at comcast dot net (Just substitute the appropriate characters in
    the address)

    Never take a laxative and a sleeping pill at the same time!!
  9. I will answer each question as I go along. Thanks for all of the feedback.
    It is a row of lamps part of 5 rows. and it just doesn't light up. I have
    no schematic and I don't know where, or if the power inputs would do
    anything. It is from a game called Cyclone. there are lights that go
    around and you press a button and try and stop it on a particular light that
    has the most tickits. I don't think it would be practical to work up a
    setup as described. There is only one of these games.
    Thank you
  10. Well, this board is one of five that controls a ring of lights. But I can't
    work on it while it is put toghter. I don't have a schematic and the chips
    are 74HC14 74HC273 74HC373 and Ten Tip22, one other transitor, two
    electrolytics, and 8 ceramic caps next to the IC's. Is there no way to
    troubleshoot without power and schemtics?
  11. I ended up doing this, but there has to be better faster way. ????
  12. All of the trans check ok, I think it was one of the chips but how to you
    isolate a chip problem with out power?
  13. That is what I did with the Huntron but every chip shows problems. I know
    every chip is not bad. I think the one bad chip influences the circuit and
    makes all chips look bad. Or maybe I am doing something wrong.?
  14. Arfa Daily

    Arfa Daily Guest

    A way that I've used in the past to reverse engineer a board and determine a
    schematic for it, is to photocopy the print side, then draw on the actual
    parts, but in schematic form rather than physical form. You can then derive
    the schematic trace by trace, scribbling them out on the photocopy as you
    go, using a coloured felt tip pen. From the number of components on the
    board, and the simple logic function ICs, should be practical in your case.
    I suppose these days, you could probably do the same thing with a scanner
    rather than photocopier.

  15. Asimov

    Asimov Guest

    "russ lavergne" bravely wrote to "All" (25 Jan 06 21:40:46)
    --- on the heady topic of "Re: Repair method"

    rl> From: "russ lavergne" <>
    rl> Xref: core-easynews

    rl> Well, this board is one of five that controls a ring of lights. But I
    rl> can't work on it while it is put toghter. I don't have a schematic
    rl> and the chips are 74HC14 74HC273 74HC373 and Ten Tip22, one other
    rl> transitor, two electrolytics, and 8 ceramic caps next to the IC's. Is
    rl> there no way to troubleshoot without power and schemtics?
    rl> Thanks
    rl> Russ

    With such few jellybean IC's might it not be logical to simply change
    them all wholesale style and never develop a migrain over it?
    It is an infallible way to fix it after all!


    .... Enter any 12-digit prime number to continue.
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