• TECH: Williams System 3 Power Supply Humming

    From Zap@21:1/5 to All on Fri Jun 18 16:13:21 2021
    I am working on bringing a Williams Lucky Seven back to life. It has no audio board, just chimes. I put in a known work MPU, a known working driver board and an aftermarket power supply. Upon power up, there was a continuous loud hum coming from the
    power supply board. I powered it down and swapped in the original power supply board, which had no visible damage. It too produced a hum when powered up. What could be causing this? What should I check first?

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  • From Tom Zapiecki@21:1/5 to Zap on Fri Jun 18 16:45:42 2021
    On Friday, June 18, 2021 at 7:13:26 PM UTC-4, Zap wrote:
    I am working on bringing a Williams Lucky Seven back to life. It has no audio board, just chimes. I put in a known work MPU, a known working driver board and an aftermarket power supply. Upon power up, there was a continuous loud hum coming from the
    power supply board. I powered it down and swapped in the original power supply board, which had no visible damage. It too produced a hum when powered up. What could be causing this? What should I check first?

    I disconnected power supply board from the transformer, and still had the hum. It is the transformer humming, not the power supply board. My old ears deceived me. What can I do about it? Is this a sign the transformer is going bad?

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  • From John Robertson@21:1/5 to Tom Zapiecki on Fri Jun 18 17:41:08 2021
    On 2021/06/18 4:45 p.m., Tom Zapiecki wrote:
    On Friday, June 18, 2021 at 7:13:26 PM UTC-4, Zap wrote:
    I am working on bringing a Williams Lucky Seven back to life. It has no audio board, just chimes. I put in a known work MPU, a known working driver board and an aftermarket power supply. Upon power up, there was a continuous loud hum coming from the
    power supply board. I powered it down and swapped in the original power supply board, which had no visible damage. It too produced a hum when powered up. What could be causing this? What should I check first?

    I disconnected power supply board from the transformer, and still had the hum. It is the transformer humming, not the power supply board. My old ears deceived me. What can I do about it? Is this a sign the transformer is going bad?


    Check the fuse on the primary (line) side of the transformer and make
    sure it is the factory recommended value.

    Check that the 6.3 light wiring isn't over fused and shorted! It may not
    be connected through the power supply regulator board.

    If above is all good, then see if the transformer windings are loose
    (unplug the game, eh?) if you grasp the paper wrapping and try to wiggle
    it. It should feel rigid. If loose try putting some hardwood wedges in
    space between the windings and the metal core of the transformer. Do not
    use metal wedges, or soft wood.

    Of course you may have a short in the wiring from the transformer
    between leads - this I can't guess where you would find it, just check
    the condition of the wires and look for pinches and bare or exposed wire.

    If that quiets it down, then great, otherwise leave the transformer
    powered up for a little while with the windings disconnected from the
    power supply board (pull any fuses). see if the transformer gets warm or
    hot to the touch. It shouldn't get more than slightly warm with no load...
    If it starts smelling or smoking then it is toasted - has a shorted
    winding.


    John :-#)#

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  • From Tom Zapiecki@21:1/5 to All on Fri Jun 18 17:55:38 2021
    I will follow these steps!

    Thanks, John!

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  • From Tom Zapiecki@21:1/5 to All on Fri Jun 18 19:00:18 2021
    John,

    Fuses good and correct rating. Playfield and backbox lightning do not go through the power supply board, and they are good. Transformer seems solid in yoke. it does not move at all. Wiring is intact, properly insulated, and I did not see any opportunity
    for a short. After running for 5 minutes with no load, transformer felt barely above ambient temperature. I would not even call it warm.

    Has anybody ever run into a transformer that just hums? I might even go so far as to say it buzzes.

    Thanks,

    Zap

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  • From John Robertson@21:1/5 to Tom Zapiecki on Fri Jun 18 22:59:25 2021
    On 2021/06/18 7:00 p.m., Tom Zapiecki wrote:
    John,

    Fuses good and correct rating. Playfield and backbox lightning do not go through the power supply board, and they are good. Transformer seems solid in yoke. it does not move at all. Wiring is intact, properly insulated, and I did not see any
    opportunity for a short. After running for 5 minutes with no load, transformer felt barely above ambient temperature. I would not even call it warm.

    Has anybody ever run into a transformer that just hums? I might even go so far as to say it buzzes.

    Thanks,

    Zap


    Check to see if any metal laminations in the transformer core are loose.
    It is good that the transformer is not getting hot!

    John :-#)#


    --
    (Please post followups or tech inquiries to the USENET newsgroup)
    John's Jukes Ltd.
    MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
    (604)872-5757 (Pinballs, Jukes, Video Games)
    www.flippers.com
    "Old pinballers never die, they just flip out."

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  • From Tom Zapiecki@21:1/5 to All on Sat Jun 19 12:27:34 2021
    John,

    Everything is tight. I tried an unorthodox method which some people had success using. I whacked it with a hammer. All that did was scuff the top of the plates.

    At this point, since it functions more or less properly, I will live with it as is.

    I do appreciate the help.

    Thanks for taking the time to respond!

    Sincerely,

    Zap

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  • From John Robertson@21:1/5 to Tom Zapiecki on Sat Jun 19 22:46:29 2021
    On 2021/06/19 12:27 p.m., Tom Zapiecki wrote:
    John,

    Everything is tight. I tried an unorthodox method which some people had success using. I whacked it with a hammer. All that did was scuff the top of the plates.

    At this point, since it functions more or less properly, I will live with it as is.

    I do appreciate the help.

    Thanks for taking the time to respond!

    Sincerely,

    Zap


    As a last resort, make sure the bolts holding the transformer together
    are all tight...

    John :-#)#

    --
    (Please post followups or tech inquiries to the USENET newsgroup)
    John's Jukes Ltd.
    MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
    (604)872-5757 (Pinballs, Jukes, Video Games)
    www.flippers.com
    "Old pinballers never die, they just flip out."

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