What does this dial on power supply do?

Discussion in 'General Electronics Chat' started by Dalaran, Dec 30, 2011.

  1. Dalaran

    Thread Starter Active Member

    Dec 3, 2009
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    I recently got an arcade machine in pretty rough shape that I am planning to turn into a 60-in-1. The game that was in it was partially functional when I powered it up, in that it would boot to the main screen but there was some flicker (just assumed it was due to ancient monitor).

    Anyways, the attached picture shows the power supply that was used for the game/monitor. My brother helped me pull everything out of the cabinet and obviously couldn't keep his hands from messing with the red dial at the top of the power supply. When I went to test it out by using a 110V mains connection to the AC connections and the GND to FG, it made a weird pulsating humming noise and the voltages were not clsoe to expected. ~2V on the +5V rail and something like 6V on the 12V.

    It didn't make sense to me that the game would boot up with the voltages this far off, so the only thing that comes to mind is the adjusting of the dial. I tried twisting this and powering on and off a few times but had no luck.

    Any ideas how to get this working?
     
  2. KJ6EAD

    Senior Member

    Apr 30, 2011
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    There's an arcade game database on the internet. You may be able to find schematics and other service tips You didn't say what game or how old but from the condition I'm guessing early to mid 80s. Games of that era commonly need to be cleaned, have all electrolytic capacitors replaced, have ground straps repaired, have corroded connectors repinned or replaced and have damaged cabling replaced. They also may need some or all of the RAM chips replaced and the monitor may need repair or replacement. Game switches and joysticks are usually replaced as part of a restoration but since you plan to add multi-game functionality, new controls are a given. Many of those older power supplies had a voltage adjustment potentiometer but I wouldn't bother with it until you've dealt with connector/cable/electrolytic capacitor issues.
     
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  3. Dalaran

    Thread Starter Active Member

    Dec 3, 2009
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    Hi,

    Sorry... I guess I should have been more clear.

    I'm not worried about the game functioning at all. I have stripped everything out from the cabinet including boards, monitor, joysticks, buttons, etc. I only purchased it for the outer shell and plan to use new electronics. The only part I was trying to salvage was the power supply as it gives the exact voltages I need. I had removed the supply and powered it up on my bench using an older power cable connected to the AC points and FG, so none of the other stuff comes into play.

    BTW - the game was Hyper Olympic, and yes from the mid 80's.

    Thanks!
     
  4. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    Is that dial a switch with detents or a full potentiometer?

    you could try changing it and measuring the output voltages, but since it only has the standard voltages like +/- 5V and 12V you could simply use a computer PSU and throw this one away.
     
  5. KJ6EAD

    Senior Member

    Apr 30, 2011
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    Never mind. That's what I get for guessing If you're just building a MAME system from scratch, why use a ratty old cabinet; new ones aren't that expensive? I agree with the advice to use a computer power supply.
     
  6. Dalaran

    Thread Starter Active Member

    Dec 3, 2009
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    Hi,

    I mentioned I would be turning this into a 60-in-1. Almost all of these boards take a +5V and +12V, so since the previous game turned on I thought I could at least reuse this supply. I will look at a CPU supply though if I can't get this working. Guess it was more my curiosity as to what this dial actually does. The dial is not a switch as it is smooth & continuous and seems like it could be a pot.

    The "ratty old cabinet" was $50, and being that it would require more than two full 4x8 sheets of 0.75" MDF I looked at it as a good deal. Seems like I'll look for an old computer power supply and use that.

    If anyone has any thoughts as to what this dial actually does would be nice for my own record.

    Thanks.
     
  7. KJ6EAD

    Senior Member

    Apr 30, 2011
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    The only thing a pot would do on a game of that vintage would be to trim the +5V supply or adjust the audio volume. Some games combined the power supply and audio amplifiers on a single PCB.
     
  8. Dalaran

    Thread Starter Active Member

    Dec 3, 2009
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    Thanks. Really just seems like an off the shelf power supply, and don't think it has anything to do with the audio portion. Sounds like its to trim the 5V supply, so likely something more drastically wrong than an incorrect dial position.
     
  9. KJ6EAD

    Senior Member

    Apr 30, 2011
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    It's a generic switch mode power supply so maybe it has a minimum load requirement. Why don't you google the model number and find out.
     
  10. Dalaran

    Thread Starter Active Member

    Dec 3, 2009
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    Besides a CAUTION warning, a 110V/220V switch and the markings shown on the front, I don't see anything else and nothing indicating a model number. I couldn't find anything this similar as they all seemed to lead me to CPU supplies
     
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