Power supply problems

CrazyKongFan

Well-known member
Joined
Apr 16, 2008
Messages
3,809
Reaction score
411
Location
Michigan
I've got a Bally/Midway Gaplus, and seem to be having problems with my power supply. It's only putting out about 5.5V on the 12V line. Gaplus works fine in it, as does a 48-in-1 board (via a JAMMA cabinet adapter), but some boards have no sound (Black Tiger) and some are horribly distorted (Crazy Kong). Just wondering what I should check first, or if there's something that normally causes this problem. I'll include pics of both the transformer block, and the regulator board (which is an MCR style, 90412-D000) Thanks in advance!

Transformer block:
attachment.php


90412-D000:
attachment.php


(oh, and if anyone notices, yes, there is a blown fuse, the right-most one in that little 4-fuse block. I had the problem before it blew, and it's only going to the coin door lights, which I don't need anyway, so I haven't bothered to replace it)
 

Attachments

  • midway-ps.jpg
    midway-ps.jpg
    93.2 KB · Views: 137
  • 90412-d0000.jpg
    90412-d0000.jpg
    94.8 KB · Views: 136
Well, lacking schematics, I'd first look at the voltage coming from the xformer assy to the regulator board. If it's already low, then I'd replace that rusty-ass fuse holder and fuses, check the rectifier diodes, and check/replace the gigantic filter cap (which ever one is on the 12V line). If the voltage from the xformer to the regulator isn't low, I'd check the transistor(s), regulator IC & filter cap related to the 12V supply on that PCB.
 
power supply

I would start by taking that out and put in a switcher.
i assume the regulator on the 12v is faulty or components around it.
 
Just order a rebuild kit and fuse block from Bob and install them. Most game PCBs need 12V for audio. The newer ones 60-in-1 etc... don't.
You should also check/replace all of your connections on the 12V line. That fuse holder looks pretty bad.
 
Last edited:
So first things first, can I pull out the transformer block and test that without the regulator board being hooked up, or does it need a load on it to test?
 
You can test the transformer without the need to pull it out from the cab. If i where you i would check the fuses for continuity first. Then, set your multimeter in AC mode (not DC) and test the (alternate) voltage coming out from the transformer before and after the fuses. The problem with a fuse block in those conditions (very rusty) is that you more than probably have bad connections...
 
Back
Top Bottom