(Topic ID: 290458)

Bally AS-2518-22 Voltage regulator problem with high voltage

By Inkochnito

8 months ago

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  • 78 posts
  • 14 Pinsiders participating
  • Latest reply 7 months ago by Inkochnito
  • Topic is favorited by 4 Pinsiders


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    #2 8 months ago

    I would just rebuild any high voltage power section as a rule of thumb... years ago I used to just replace the faulty part, only to find that something else would fail within a few weeks. Did you check the voltage at the base of Q22? Should be around 193VDC. The zener is a part of the reference circuit. If you want to know the theory of operation, Google series pass transistor regulator.

    #4 8 months ago

    These circuits can be designed and drawn in hundreds of ways but the concepts are the same. Q21 is the series pass transistor. Q22 forms a Darlington Pair with Q21 to increase current handling. Q23 is the error amplifier. If the error signal changes the transistor amplifies this signal and feeds it back to the base of the series pass transistor to adjust its effective resistance.

    If you are only getting about 100 VDC out at TP2, the top of divider network formed by R54/RT1/R56, something is certainly amiss. It might be a component or components, but if not you may also have to check ALL the interconnections between them. That's why I suggest starting with checking all the noted voltage points, but all those should also be present at all the components connected to them (i.e., you should have around 193 VDC at the base of Q22, one side of C27, one side of R51, the collector of Q23, and one side of C28)

    1 week later
    #29 8 months ago

    You should desolder one end of resistors in complex circuits to get accurate measurements.

    1 week later
    #47 7 months ago

    So you bought 40 transistors to fix one game? Geez, why not leave some for other folks trying to fix their games?

    #54 7 months ago
    Quoted from Inkochnito:

    Nope, I fix boards for a lot of other people.
    This will allow me to fix 20 boards.
    They'll be gone in a year or so, maybe two.

    I kind of figured that might be the case. Though I do suppose some might hoard parts, as long as you're making use of them it's good.

    #57 7 months ago

    That's why the aftermarket supplies are a no brainer. Highly efficient linear designs that generate less heat, short circuit protection, 5 amp 5V rails, LED indicators, mosfet drivers for faster coil response and more. It's one thing to save an expensive MPU board with a few dollars in parts, but replacing a power supply or solenoid driver board with an aftermarket board for years of reliable operation often makes more sense.

    #59 7 months ago
    Quoted from pins4u:

    I think you mean:
    "Highly efficient SWITCHING designs"
    Linear is what the originals are......

    No. Linear, as stated below. Anyways, really not a debate, but an option. The prices are so affordable on a lot of the aftermarket stuff, if you want to save time and get one up and running quick and reliable.

    Screenshot_20210415-201326 (resized).png
    #61 7 months ago

    Well, really they could have simply said "modern" designed power supply and that would suffice. The choke input will give much better voltage regulation over a varying load vs. capacitive input. My personal preference is if a supply needs a minor repair such as a filter cap I just make the minor repair and test it, but if it needs a lot of work, just replace it with a new supply and and move on. That's the first thing I overhaul when restoring a game - start with clean, reliable power. It's the heart of the game.

    #64 7 months ago

    G-P-E In your professional opinion is a new supply, even with this design flaw, still a better option than significant repairs to a 20 or 30 year old supply? Another thing to keep in mind is not all aftermarket supplies are the same, with all the different games and aftermarket companies out there. I've only had a few Xpin and Rottendog supplies and they worked very well.

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