Special Forces Just Stopped Working

[kmssd]

We have a Special Forces Kung Fu Commando arcade machine which I think was converted from a Donkey Kong Jr game. My dad said it just stopped working one day and I'm trying to see if I can get it to work. I tested the three fuses I found and they are good. The monitor seems to work (I power it on and can see it light up). I also checked the three wires soldered on as per the instructions of the conversion and they are still making connections. What are some commom problems to check for?

[HHaase]

The other guys will know more than me what to look for specifically, but I'll get some questions your way to help them pinpoint it out.

What about audio, any sounds coming out at all?  I.E. does it seem to play, but just with no video?  Or is it nothing happening at all, other than a blank monitor that's powering up?

Tested the DC voltages coming out of the power supply yet?  Got a voltmeter?

-Hans

[kmssd]

No game sounds, but the speaker hums like it has power. I will test the power supply and edit my post with results.

[SirPeale]

Photos will be key here.

Check power supplies for voltages - both in and out.

Check boards for voltages going in, inspect for obvious damage (ie burned parts, etc).

[kmssd]

Didn't get to check the voltages yet, but I did do a quick search for blown out capacitors and stuff. I can do a more thorough check when I take the boards out. I do have some pictures too.

[kmssd]

Sorry for the little hiatus there, I got sick and didn't get to check until now. Using my radioshack meter I checked the voltages coming in and out at multiple spots. Most readings were good, some I didn't get any readings. These were the bad ones, both +5 vdc out of the PS to the Video PCB, both +5 vdc and one +12 vdc from the PS to the CPU PCB. I made a drawing of my findings if anyone wants to see what I'm talking about.

Scratch that, I didn't read the -5 and +5 right so really that power supply checks out 100% on the meter. Now I don't know what to check for as the only thing I can see wrong is something with one of the two PCBs and anything past a visual check and checking with a meter, I wouldn't know how to diagnose it.