(Topic ID: 211493)

Mr and Mrs Pac Man Pinball Sound issue

By dbzap19

6 years ago



Topic Stats

  • 5 posts
  • 4 Pinsiders participating
  • Latest reply 6 years ago by jj44114
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    #1 6 years ago

    Bally AS 2518-61B

    I read an old post from bonedoc and shimoda concerning negative voltage from 7905, -5V Regulator on the Bally Squawk and Talk. My TP4 reading on this board is coming in with a crazy -105 reading vdc when it should be a -5 vdc. TP2 was in specs at +5 vdc. TP3 was 15 for a +11.5 vdc spec. The board caps have been replaced and the volume pots replaced as well. I am getting a hum only from the board. I checked the speaker and it seems to be in working condition. I ran a test speaker wire and get the same noise/hum so I am assuming the wire is good. The board was tested on a Bally Test board and worked properly after caps and pots replaced (Marco Replacement Cap set). Were these similar symptoms for anyone else before replacing the 7905? Also where did you purchase the part from?

    Thanks for your help. This has been a very frustrating restore of a Mr and Mrs Pac Man pinball. This is the last issue for the machine to get is playing properly.

    Any ideas are appreciated to point me in the right direction.

    #2 6 years ago

    Are you sure you are measuring the correct board? It should be next to impossible to measure 100+ volts on the S&T board.

    #3 6 years ago

    That -5 comes off the GI so there is no way you're seeing -105V unless you're seeing it through a cloud of smoke. My guess is you're reading -105mv. Check your input of the 7905. There are only two diodes and two caps in that feed circuit so it shouldn't be too hard to troubleshoot.

    #4 6 years ago

    Doubtful that the 7905 is bad, they rarely are. You must be measuring test point 4 incorrectly. At over 100volts you would blow a few capacitors at a minimum. Make sure you use ground on the board for your black meter lead, not the ground braid or any thing else.

    #5 6 years ago

    How many flashes on the S &T led when you power up the board?

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