(Topic ID: 104691)

7-switch opto board problem ? (part A-15576)

By Leo13

8 years ago

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    #1 8 years ago


    I think the switch opto board is giving me problem.
    Sometimes, the ball-through is not registered (so you wait for the game to finally activate the coils), and sometimes the ball ejecter under the glove activates even when there is no ball on it.

    The optos work well in test mode, but fail randomly during a game.

    Do you think I have to replace the board, part number A-15576, or the problem can be elsewhere ?


    #2 8 years ago

    You know ... there's not much that can go wrong on those boards ... pretty much boils down to one of two issues :

    Bad LM339s
    Broken power resistors

    So, check that the power resistors haven't cracked loose from game vibrations, and replace the LM339s with new ones (install sockets to ease any future repairs).

    99.99% of the time, that fixes things, presuming the issue is actually in the board, and not in the optic elements (or wiring to/from).

    #3 8 years ago

    I've redone 2 solders today that were not in gret shape, but it did not change anything.
    I think I have to replace the 2 LM339. I hope my soldering skills are good enough !

    If not, nobody is selling this 7-switch opto board ?

    #4 8 years ago

    I've got 4 or 5 in a box, can test and repair one for you if you need one. Just send me a PM.

    #5 8 years ago

    Send you a PM

    #6 8 years ago

    Problem fixed. Thanks.

    #7 8 years ago

    What was the fix?

    #8 8 years ago

    I bought a working board from a fellow pinsider.

    I have ordered some LM339 to practice my soldering skill and hopefully I'll have a spare one in case of a new problem.

    #9 8 years ago

    Since you're local, I can help you if you like swapping the 339s. WMS boards are pretty easy to solder on.

    #10 8 years ago

    Very kind from you, thank you very much ! I'll contact you in pm for sure. And guess what, we have a 3-days week-end ahead

    6 months later
    #11 8 years ago

    Just wondering if you ever replaced the 339's. I am doing the same thing this week. I'm sure there are others who would like to know how it went.

    #12 8 years ago

    You might also check for any "vias" on the board (through-plated solder connections from traces on the top to traces on the bottom of the board) and reflow those if the solder looks iffy. I have an early production Scared Stiff with a 16-opto board that would on occasion show an closed indication for the trough jam or trough ball switches, and it turned out to be a crappy connection between a trace that dipped from the top to the bottom of the board; reflowing the solder in the via permanently resolved the issue.


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