Pinball Machine... driving me crazy

Discussion in 'The Projects Forum' started by Dalaran, Mar 31, 2010.

  1. Dalaran

    Thread Starter Senior Member

    Dec 3, 2009
    I have quite a strange problem with my pinball machine project. Please see the 2 links below for the power wiring/supply board schematics of my system.

    Power Wiring Schematic

    Power Supply Board Schematic

    With nothing connected to the secondary of the transformer I draw ~450mA, which seems reasonable to me. With all fuses unplugged it only takes hooking up 3J1-12 to the power supply board and I draw 4A. This is a ground pin (center-tap of 2 x 9.3VAC) and I am getting crazy current consumption.

    Originally the machine came to me with a cooked transformer, and I had recently replaced it. I'm guessing whatever caused the last one to go will soon take its toll on this one. Any ideas what might be happening? I am completely lost.

  2. retched

    AAC Fanatic!

    Dec 5, 2009
    All fuses removed and current draw on the ground leg?

    Have you tried a continuity test on all fuse holders with power off, to check for possible shorts?

    Im trying to follow the schematic and run into fuses..

    If one of the transistors have failed shorted, you could be getting feedback, but it would require a return to hot :rolleyes: ...via a fuse...


    Solder bridge?
  3. Dalaran

    Thread Starter Senior Member

    Dec 3, 2009
    Thanks. Same thoughts I was having. I do not have any shorts between any of the pins on 3J1 (except the grounds as expected) and all seems normal. I removed the power supply board and all looks good. Only one capacitor seems to have been replaced, the solder job is not pretty but there is nothing to bridge it too close by. This is why I am shaking my head. Just not even sure where to keep looking.

    I guess this means however that somewhere on my ground (runs throughout the entire machine) I must have a short to hot? Possibly only manifests itself with the power on? As I mentioned, power off, I do not see anything unnormal on either the supply board or power wiring.

    Thanks for your time.

    edit: I am thinking of removing the ground from where the mains plug comes in and connect it directly to 3J1-12. This way there is nothing else on this ground connection so ideally I won't see this large current draw. Then I can work from here. Thoughts?
    Last edited: Apr 1, 2010
  4. SgtWookie


    Jul 17, 2007
    Is 10J1 disconnected? There is no fuse in that line.

    If it is, then make sure that C15 is not shorted.
  5. Dalaran

    Thread Starter Senior Member

    Dec 3, 2009
    Thanks for the reply. 10J1 is disconnected. I have also lifted the anode leg of both diodes D7 and D8. I checked C15 for sanity reasons and it is not shorted.

    All other help is appreciated.

    Thanks all.