(Topic ID: 331648)

Demolition man. Some lamps intermittently not working.

By Kingofmetal

1 year ago


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    #1 1 year ago

    Hi all.
    I have a DM pinball and an issue with 8 lamps in the centre of the playfield intermittently not working. extra ball, Multi ball, 2 lamps that enter car crash and 5 others. I have checked connections in back box, and the connection under the playfield onto the lamp board, and the connection between the playfield and the back box all seem ok. Am I looking at a ground fault? Also could a faulty lamp cause others not to work.
    Thanks in advance.

    #2 1 year ago

    All pinballs that age that come through my shop will get the lamp boards pulled off of the bottom of the game, and the solder connections to the plugs reflowed.

    Cracked solder connections on the board, at the plug, is where you should look first.

    Your manual is here:

    https://www.ipdb.org/files/662/Williams_1994_Demolition_Man_Operations_Manual_English_OCR_searchable.pdf

    Look at the lamp matrix.

    (Hint, it's on the second to last page, what would be the inside cover of the back...)

    Extra Ball and Multiball are both connected to the yellow-black wire.

    Are all your problem lamps on the yellow-black wire?

    Examine the plug coming into the lamp board, is the yellow-black wire partially pulled out of the connector?

    Examine every other lamp connected to the yellow-black wire. Are all the connections secure?

    This is one of those situations in pinball that really confuses new technicians.

    I have problems with every lamp on the yellow-black wire! IT MUST BE THE WIRE, OR THE CIRCUIT!!! (Nope, you have eight individual bulbs out...) Hehe.

    Replace the bulbs involved.

    My usual technique now is to get into all lamps test (Test 10 to get the flashers also, just for fun).

    With all the lamps blinking, I'll take a black twist in socket that has a working lamp, unscrew it. I put it in the place of the dark lamp. This helps with the problem of the lamp in the black socket not making connection inside the black socket. When you take a working lamp and black socket and put it into a lamp board, you have narrowed the problem to the lamp board and it's wiring.

    Then I put a new bulb in the black twist-in socket, and put that socket where I pulled the working lamp out of.

    I know this sounds funny, but a frequent problem is the tiny wire on the 555 bulb not making connection inside the twist-in black socket, and doing it this way is helpful.

    Let us know what you find!

    #3 1 year ago

    Thank you for taking time to reply.
    Lamps affected are: 47,45, 46, 48, 42,41,43. 44.
    All in column 4 yellow/black J137/4. Lamp 38 column 3 plays up as well but I will check the bulb and connections on the holder.
    I’ll do the tests you suggest and come back.. As an aside the bulbs all seem to work fine on initial start up then play up when machine warms up.

    #4 1 year ago

    Just had a look.
    One thing I have noticed is that my column 4 is plugged into J138 not J137.
    According to the manual j138 has no connection.
    Should I just go ahead and plug into J137.
    I don’t want to cause more problems.
    Thanks.

    #5 1 year ago

    That plug is fine, they are completely parallel circuits. You might want to put it in there to test though which will tell you if your j138 connector was the issue.

    #6 1 year ago

    Hi, plugging into J138 makes no difference to the problem.
    I’m wondering if the connector is worn on the pins.

    #7 1 year ago

    Update. Changed plug on J137. No difference.
    Took all the bulbs (8) that are not working and replaced with known working bulbs.
    No Difference.
    I have continuity from the plug J137 down to the plug on the playfield.
    Where do I go next or am I assuming it’s a fault on the board in the back box.
    Thanks.

    #8 1 year ago

    Thanks for replacing the bulbs anyway... you'd be surprised at how often these light problems are light bulbs instead of technical problems.

    And thank you for testing the wire continuity... a broken wire is another common reason a whole string of lamps won't light.

    The lamp circuit is fairly simple, and on the lamp matrix chart, up top where it says yellow-black wire, it says what we are looking at is J137-4 (or J138-4), and Q95.

    Manual page 3-4 (Pdf page 108) shows the circuit for how lamps are powered.

    There isn't much to go wrong, so replace Q95 with a TIP-107 transistor.

    In my experience, the TIP-107 solves the problem four times out of five, with the other times needing U19 (ULN-2803), and/or possibly U18 (74LS374).

    Good luck!

    #9 1 year ago

    Thank you pinretail for your reply.
    Q95 looks newer than the others so had obviously been changed before and I can see a small repair to the circuit board by u19.
    U18 & u19 sit off of the board slightly do they just plug in?
    Is there a way of testing Q95 before I remove it?
    Can I change U18&U19 before I change Q95. ?
    Or shall I just change all 3 regardless.?
    I’m trying to avoid taking the whole board out if poss.
    Thanks.

    #10 1 year ago

    Update.
    Q95 tested and found to be faulty.
    Q91 tested and showing shorted if I put a DMM on the metal part back to 18v test point but strangely still working the lamps???? Will replace it while I’ve got the board out.
    One other small question.
    As I don’t really use the cabinet flipper buttons I get the message check flipper switches on start up. I thought this only came up if switch was not used every 60 games or so. I seem to get the message nearly every time I turn it on.
    Thanks.

    #11 1 year ago

    Another update.
    DMM test TP 8 to metal plate on transistor
    Q91 shorts. (But lamps worked)
    Q95 no short ( lamps not working)

    Put a jumper across the metal plate of a known working transistor to Q95 - lamps work.
    So while I’m changing Q95 I thought I’d change Q91 as it was showing a short.
    Result:
    No lamps work at all on the columns controlled by Q91 or Q95.
    If do the TP 8 test no shorts. If I do the jumper from a working transistor to Q91 lamps work but they don’t for Q95.
    Before I put the board back I did check the solder points of the transistors I changed to points further down the board to make sure the joints were good and they were.
    HELP!!!

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