(Topic ID: 330926)

TECH - Bally Solenoid Driver Board HV

By Dietrich8403

1 year ago



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    #1 1 year ago

    I got a Kings of Steel years ago and finally am getting around to fixing it.
    The driver board HV had visible burned resisters at R51 and R55 so I rebuilt the whole section with components I had from GPE or acquired from NTE.

    Before putting it back in the game, I was checking paths with my meter and have an issue at R56(82K).
    Meter reads 81.7K with red lead at junction of R56 and RT1, and black lead at junction of R55/Q23/C28.
    Meter reads 77K with red lead at junction of R55/Q23/C28, and black lead at junction of R56 and RT1.
    Position of RT1 (which is also new) only changes the value from 76.4K to 77K.

    If I remove either R55 or VR1, R56 will read 81.7K with the leads in either direction.
    R55 and VR1 both meter properly, both in and out of circuit, and I've tried additional replacements with the same results.

    The board has not been powered up yet so I do not know if voltages are proper or not. Thoughts on this discrepancy of ohm readings?

    Thanks
    Dan

    #6 1 year ago

    Thanks for all the thoughts.

    All transistors have already been replaced.

    I also tested a couple boards from my shelf and get identical readings in both directions, so that is why I'm a little confused by this one.
    Wasn't sure if the 4K ohm difference is to be worried about.

    When I lift one leg of VR1, I get .594 in one direction and open in the other so it tests fine.

    Unless something else jumps out at anyone, I will put it in the game and see what voltages I am getting.

    #7 1 year ago

    I installed the board and tested with F1 out and had regulated HV.
    I was able to tune it easily with the new pot, so I tried again with the fuse in and have no issues.
    Apparently the ohm discrepancy is not of concern.

    Thanks to everybody for the input!

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