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(Topic ID: 310997)

System 11 HV Power Supply issues

By Homeslice666

2 years ago



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  • 6 posts
  • 3 Pinsiders participating
  • Latest reply 2 years ago by GRUMPY
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    #1 2 years ago
    OP
     
    ???

    Homeslice666

    Inactive member

    Unknown

    2y 12,300 42 3

    I'm trying to figure out where I went wrong with my power supply.

    I have an Alley Cats that had intermittent light issues. Replaced the header pins on the power supply boards and had complete success! Until the small piece of Flux I missed while cleaning caused two pins to arc together. This can be seen in the attached. Oops.

    Much shame and diagnosis later I realized I had an issue with the high voltage section. At 3J5 I should have -100V, +100V, and +5V. I had -100V, a fluctuating voltage at pin #4 where I should have had +100V, and +5V.

    Figuring that my high voltage section needed rebuilding, I replaced diodes and resistors for the 91V mod as per Vid's handy bulletproofing guide.

    ...I now have no voltage at pins 4/3, where I should have -/+ 100V or now 91V. When I read it with a DMM, they read 60ish volts, then drop to 0V over a few seconds.

    I'm stumped. I have continuity as far as I can see. Please help!

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    #2 2 years ago
     
    JWH

    Shogun00

    Pinside member

    6y 60,550 948 60

    Alley Cats? Is that a shuffle alley machine? Or are you talking about Bad Cats?

    Anyway, the high voltage circuit is only used for is the plasma alphanumeric displays. If they were working, then you should have left the connector alone.

    You most likely have blown something when you crossed the traces.Check the fuses and caps first, then recheck your work.

    What do you mean by "intermittent light issues"? Are you referring to the lights in the backbox?

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    #3 2 years ago
    OP
     
    ???

    Homeslice666

    Inactive member

    Unknown

    2y 12,300 42 3

    Yes, this is a System 11 Shuffle Alley.

    I had weird intermittent light issues before replacing the header pins. Some of the strike/spare lights would randomly not work. GI circuit has always been fine.

    Yes, the displays are dead. I was blowing the HV fuse prior to rebuilding the HV side. I actually blew a chip on the display board so I bought a whole new board from TNT.

    Caps are recently replaced and show no visible damage.

    I swapped in a known working power supply from High Speed and it functions 100%, so I believe I'm limited to power supply issues.

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    #4 2 years ago
     
    DEC

    GRUMPY

    Pinside member

    10y 95,050 8,703

    Well you shorted pin 3 to pin 4 which shorted the +100 to the -100 volt line. I would assume that either or both Q-1 and Q-3 are bad. I would test them first. You should have replaced D-3/ D-4 when you rebuilt the power supply. I would replace them now with 1n4007 diodes. If you find that you need to replace Q-1/Q-3, they are obsolete. There are suitable replacements available but have reversed leads so the leads need to be crossed for installation. Also the carbon between pins 3 and 4 needs to be remove as carbon is conductive and will arc again.

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    #5 2 years ago
    OP
     
    ???

    Homeslice666

    Inactive member

    Unknown

    2y 12,300 42 3

    Thank you for your help Grumpy!

    I'll clean the carbon out from pins #3 and #4. Should I infill the gap with anything?

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    #6 2 years ago
     
    DEC

    GRUMPY

    Pinside member

    10y 95,050 8,703

    No, not necessary.

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