K4900 "hula" issue

hatrick

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Recently recapped 4900, new voltage reg, new filter cap, solder joints gone over and fixed, etc.
Checked b+ at r503. At end closest to fuse, it's about 124 volts. At other end it's about 160 volts.
This situation isn't on the flow chart and I haven't seen it before. Same situation with two different voltage regs.
Any ideas?
 
Have you ruled out cabinet issues? Hula can be the fuse to the monitor (in the cab), the power supply for the gameboard, the gameboard itself, even bad connections on the wiring in the a/c section of the cab.
 
Have you ruled out cabinet issues? Hula can be the fuse to the monitor (in the cab), the power supply for the gameboard, the gameboard itself, even bad connections on the wiring in the a/c section of the cab.

I haven't, but aren't the b+ readings way off? I assumed it was a monitor issue based on that.
 
No, they're not off that far, 124, I think it's supposed to be 130 or so. That's close enough... when you have a wave from B+ it's way low, yours is within 5%. They made different revisions of those boards with slightly different caps, they've probably all got a slight variance in B+ anyways.

Try plugging it into a different cab if you can, just to rule all that mess out.

BTW, if the cabinet has screwed up A/C voltage driving the monitor and isolation transformer, that would lower your B+ slightly as well (and could cause the hula). If you just unplug the video that will rule out the power supply and game board, you can probably tell if it's doing it without the video on.
 
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Thanks for the suggestions. I'll definitely try the monitor in a different cab. It's funny how we (I) can get hung up thinking the problem is one thing and not even consider other possibilities.
 
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