Centipede PS Voltages

Eclipse860

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Hello, I am new to the Arcade world. I found a couple Centipede Cabinets in Poor-to-OK condition. One Cabinet has a Power Supply AR-Board and all wiring harnesses. I figured I would start by checking the Voltages on the PS then the AR. The numbers for the DC voltage on PINs 1-3 are a bit off. Should I be concerned?

  • Power Supply Testing
    • Pins 1, 2 and 3
      • All mine measure 14.7 VDC - Seems HIGH
      • I do no need to hold back panel switches in
      • Will get readings if not powered on and capacitor is charged
    • Pins 6+ - VAC
      • Make sure to hold both panel switches (front and back of cabinet)
      • Make sure Power Switch is ON (Flipped on is to the right)
    • Pins 6 / 7 - 37.8 vac
    • Pins 7 / 9 - 8.6 vac
    • Pins 10 / 11 - 32 vac
    • Pins 10 / 12 - 64 vac
    • Pins 13 / 14 - 32 vac
    • Pins 13 / 16 - 64 vac
 
Quick tip, if you pull on the interlock switches, you don't need to hold them in (what you refer to as "back panel switches"). They will stay on.

Also, you can quickly test your Big Blue by doing this:

Del
 
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Transformer block Pins 1,2,3 are normal voltages. They are unregulated power.
I'm guessing your wall voltage may be over 120vac too?

Your ARII - 13vdc is bad . Should be 5v+ That can be the 2N3055 or the LM305 (or both)
 
I agree. I'd bet it is indeed the bottle cap transistor. Beware of cheap fakes when you replace it. Here's a trustworthy source to get one:

I'd try swapping that first since it's pretty common to go bad (in my experience). The LM305 voltage regulator is pricier, so I'd see if the 2N3055 solves your issue first.

Del
 
Awesome! Thanks for all the tips guys. I have marching orders. And pulling the Interlock switch.. that makes soo much sense now. During my initial T-Shoot, I only had to push the one at the back of the cabinet... after pulling the harness to put everything on a bench, I also pushed in the interlock switch on the front of the cabinet. Took me forever to figure out why I could not get AC then was perplexed that I had to push both in.

Again, thanks. I
 
Thanks again for the tips. I ordered parts from suggested site. I changed out the 2N3055 - No change in voltage. I then changed out the LM305. Also no change. Advice on where to go from here? I dont mind throwing some money at it.. its fun practice and not terribly expensive.
 
Measure the impedance of the two 10ohm sense resistors R29 and R30. If one or both are out of spec (i.e. kohm or Mohm), you will have over-voltage.
Even if they are not "burnt" looking, measure their actual resistance.
 
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Note: R29 or R30 do not need to be "open". I have had over-voltage when one was 1kohm (approx) instead of only 10ohm. "Open" is relatve.
The resistors should be 10ohm +/- 5%.
 
Lol, got it. Will test, replace if needed and report back.
 
That was it! Both those were bad. Replaced with new and now have 5+ and the POT is adjustable. Not sure how I missed R30.. it was black. R29 had a little bubble sticking out of it.

Now a double check of all voltages and I am going to hook up the PCB I got a couple days ago!
 
Sense resistors fail due to bad edge connector. Check the PCB edge and the wire harness pins. Clean the edge connector. Review before powering for an extended time or you'll be repairing the ARII again.
 
To clarify, the edge connector is probably not bad (i.e., in not need of replacing). It's just dirty. This is a very common issue for all Atari games.

The sense resistors burn up when the main 5V and/or ground paths between the AR and game board get blocked or broken somehow. This most commonly happens when the fingers of the game board become oxidized and/or dirty, which happens to all of these boards after many years.

The oxidation is resistive, and blocks the relatively high current (2-3 amps) that is present on the 5V and GND wires, going to and from the board (as the same 5V current that goes to the board from the AR, returns to the AR via the ground lines.) When this current gets blocked, the AR basically ends up forcing that current through the sense resistors, as they provide a secondary path to/from the game board.

Normally these paths don't handle much current (as they are only used by the AR to sense what the voltage is at the game board). But when the main 5V/GND paths get blocked, the current goes through the sense resistors instead, and burns them up.

The solution to this is to just clean the edge connector fingers on the game board. It took many years of neglect to oxidize to the point of being a problem, and a simple cleaning can fix that. You need to scrub them with something abrasive, to remove the oxidation. A fiberglass pen is recommended, get one on ebay. Then get a can of DeOxit, and put some on the fingers after you've cleaned them with the fiberglass pen. Here are links to what you need, get them:



Doing this once every couple of years will keep the fingers clean, and will prevent the problem from happening again. You should clean the fingers on every game board, however this is especially important for all Atari games.

For now however, you should check the wiring between the AR and game board, to make sure the GND and 5V paths (which are the outermost and second to outermost pins/wires on the edge connector respectively) are not broken. Look inside the edge connector and make sure the pins aren't bent. And make sure the wires and crimps are intact between the AR and game board.

Otherwise if there is a break, the sense resistors will burn up again instantly, as soon as you apply power again. So when you power up, I would have a DMM on the 5V test point of the game board, and I would watch it, and watch the AR, and be ready to kill the power instantly if anything smokes.
 
The PCB does fire up and test modes work. The CRT unfortunately is really bad. That will be my next project. For now I have it using a RGB to VGA converter which doesnt look right. I am hoping it is not the PCB as everything on it is supposed to be functioning properly. I will open a new thread for that. Just wanted to say thanks for getting me this far!
 
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