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#8 Classic Bally / Stern High-Voltage Section

Discussion in 'The Menace Files' started by Menace, Nov 12, 2014.

  1. Menace

    Menace Well-Known Member
    Staff Member

    Nov 14, 2012
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    Santiago de Aurora
    If anyone has a classic Bally or Stern title in their collection at any point, one of the easiest and most important things to check is the high-voltage section on the solenoid driver board for the correct voltage. (assuming your displays are working) The reason this is so important these days is to avoid burning up your displays, which can be difficult and costly to replace.

    The HV section generates 240VDC for the displays, but they only require 190VDC to operate correctly and this is accomplished by a voltage adjustment potentiometer. There are a small number of components in the HV section, and I have found the weakest link in the chain here is this pot. Given the age of these and the cheap quality used by the factory, you will often find these have failed. When this happens the circuit was designed to continue working so the game was still able to operate on location, but as you can guess it pegs the display voltage at the max 240VDC and will severely shorten your plasma displays life. Toss your DMM on VDC, black lead to ground and red lead to TP2 which should read anywhere between 150 & 190VDC and TP4 which should read 240VDC. (please take care when poking around in the HV section, as 240VDC will give you a pretty good bite)

    This picture is a perfect example as to why the HV section in my Centaur 2 failed;

    HV1 (Large).jpg

    This pot has the entire wiper section completely missing, so no adjusting this bad boy...

    And what it looks like after replacing the pot with a new higher quality 25K pot;

    HV2 (Large).jpg

    Now, there are other components that can fail in the HV section but I've found that if TP2 is out of spec and/or nonadjustable the culprit is *usually* this pot.

    Last edited: Mar 18, 2015
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  2. Bally Boy

    Bally Boy Member

    Dec 14, 2012
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    Just another note on this HV section as well for the new owner of these older games.....

    Most Bally/Stern games can actually run as low as 150VDC to the displays, but I have had the most success around 160VDC, this adjustment is meant to increase your glass score displays life as Doug stated. You adjust that voltage using the pot Doug has replaced and measure on TP2 to ground. Make sure when you're done to replace the plastic cover too, protects the HV section, but mainly protects you from high voltage blasts! )

    The low end of the voltages can vary from game to game ( depends on the age of your glass and condition ). Sometimes with these lowered voltages, your displays may take a couple of seconds to all come on at start up, but it seems to be worth it for the long run...

    Great repair tip Doug, keep them coming, we appreciate you taking the time to post these!
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  3. spiroagnew

    spiroagnew Well-Known Member
    Staff Member

    Dec 1, 2012
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    Scotch Block, ON
    For the high voltage section of classic Bally/Stern, you will be looking for a 25K Ohm 1/2 Watt pot...here are some links to where the part can be found. Menace, correct me if I'm wrong on any of this.

    Digikey: Bourns-Inc. 3362P-1-253LF Trimmer Potentiometer, Part Number 3362P-253LF-ND

    Great Plains Electronics: Cermet Trimmer, 25K Ohm, 1/2 Watt, Part Number 3362P-1-253
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