MCR Power Supply 90412 Voltage Issues

ManiN

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So I recently got a Spy Hunter that has some voltage issues. The 5v is running around 6.4V and the 12v is at about 14.5V which both were non-adjustable to correct. I threw a Bob R. kit on it and now the voltage seems to sit at the same levels but is now adjustable. Only bad part is when both pots are turned down, they are those levels. It only goes higher in voltage from there... What would be causing this 'shift' in voltage? Does the main power supply feeding the 90412 possibly have issues? What checks could I make on the input line, any specific voltages that should be coming in to the 90412? Thanks!
 
Bump for an interesting thread.
 
Depending on what revision of 90412 you've got, this could be normal. The early revisions do not regulate without a load (IE: motherboard plugged in). Later revisions changed this. Post a picture, and I can tell you.

Edward
 
Here's a shot of the A082-90412-D000:
90412.jpg
 
That one is a later revision. It should regulate on it's own. Check resistor R219. Yours looks kinda burnt (could just be the lighting). If R219 is open, it won't regulate. It's 68 ohm 1/2 watt.

Edward
 
Is that an on-board battery in the lower left corner or a cap?

If it's a battery I'd get it the hell off the board now...
 
R219 seems is fine. I pulled it and it tested fine. R111 is rather cooked looking, but it tests spot on. I think I'll look some more for bad traces and solder. Not sure what else it could be at this point.
 
Is that an on-board battery in the lower left corner or a cap?

If it's a battery I'd get it the hell off the board now...

It's new. It's a temporary location until I get all the bugs worked out of the machine pulling the boards and putting them back in over and over.
 
OK, but you want to move it off board when you're done or it'll eventually leak and tear up your boards.

I have mine hooked to a cordless phone battery via some wire and it's all wrapped up in a plastic baggy.
 
That one is a later revision. It should regulate on it's own. Check resistor R219. Yours looks kinda burnt (could just be the lighting). If R219 is open, it won't regulate. It's 68 ohm 1/2 watt.

Edward

Is there a schematic for this version of the board? I can't even find a R219 in the A082-90412 schematic I am looking at. It's the one from the Tron manual.

Are you testing this without the board stack (J4 removed)? If both 12V and 5V are high, it seems likely that there is something in the ground or harness causing both to be regulated too high.

Individually, you could check R111 (6.8 Ohm), R112 (68 Ohm), R115 (160 Ohm) and R113 (1.2kOhm) for the 5V circuit, and R102 (68 Ohm), R106 (270 Ohm), and R107 (6.2kOhm) for the 12V circuit.
 
Is there a schematic for this version of the board? I can't even find a R219 in the A082-90412 schematic I am looking at. It's the one from the Tron manual.

Are you testing this without the board stack (J4 removed)? If both 12V and 5V are high, it seems likely that there is something in the ground or harness causing both to be regulated too high.

Individually, you could check R111 (6.8 Ohm), R112 (68 Ohm), R115 (160 Ohm) and R113 (1.2kOhm) for the 5V circuit, and R102 (68 Ohm), R106 (270 Ohm), and R107 (6.2kOhm) for the 12V circuit.

Tron has an earlier revision.....although, the schematics show this resistor....it's R300. It's was literally tapped to the legs across C106. You can see it on the "assembly drawing" page of the schematics. The Wacko manual has a schematic of a later revision...page 25-26.

http://arcarc.xmission.com/PDF_Arcade_Bally_Midway/Wacko_Parts_and_Operating_Manual_(Feb_1983).pdf

Note the schematics have a typo. This resistor is mis-labeled R118, but on the "assembly drawing" it's labeled R219. Plus there's already a R118 in the audio power section.

My guess for the OP......you've got a broken trace somewhere. Have you replaced any of the connectors? It's real easy to break one of the vias. The big bottle cap transistors on the heat sink are another common breaking point. I've had plenty of those come through the shop where some one in the past has broken a via trying to remove those transistors.

Edward
Edward
 
Yeah, I already found one spot with a bad trace on one of the bottle caps. I'll keep checking and searching. Those connectors were a huge pain, so I'm going to double check all of those too.
 
Had some time to mess with the PS some more and found I hadn't repaired that trace on the transistor well enough, now she is working fine. Sure would be great if someone reproduced those PCBs... :)
 
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