u5000 issues

supercharged

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I have a Wg u5000 series monitor in a cruis'n world that recently went into high voltage shutdown.

traced the failure to a Horizontal transistor C3686. I replaced it and turned the b+ down as far as it would go and it tested at 128V.

I know it was a little high but it was working fine and did so for several weeks.

I moved it a few feet and turned it on. No pic. Just the familiar tick of shutdown.

It has been recapped and before I put another transistor in it; I want to know what might be the problem with the voltage?
 
Wg5000

While the 128VDC on what is usually 118VDC at TP202(Im assuming your measuring it there) is high..not sure thats what caused the chassis to fail whem moved. I would check the horizontal output transistor if shorted, then remove it and measure the B+ at TP202 with it removed. See if you cant get it down to 117 0r 118 at TP202 with the HOT out. C117 in the power supply has been a culprit, but at any rate you can load down the supply at TP202 with a 100 Watt light bulb IF you have a variac. Also I have seen cold solder joints cause the HOT to fail.This would jive with you moving the game. Do you have the schematic and service manual? Wells has it
for download.

http://www.wellsgardner.com/service/
 
I'm working on a similar issue currently. B+ is at 125vdc but no picture. It clicks once when power is applied, and that's it. Voltage at TP203 is only about 5.7vdc..

Right now I'm thinking it's in the startup circuitry. There was a big burned spot around Q708, and much of the traces had burned off along with some of the board. I replaced Q708, R760, R765, Z705, and W114 - which some were bad and all were in the affected area - and this is what I'm left with. Those parts now measure the same as a working chassis I have here, but I need to check some other parts in that circuit to see if there is anything else.

I did the light bulb check and got the B+ to drop to 114 with the bulb lit, so the PS section seems to be okay.

I'll let you know if I find anything...
 
Well, I had it running perfectly for about 15 seconds, then it went back to doing this. Not sure what changed. I'd installed a few jumpers and then it powered up. I turned the brightness down and went to apply a video signal and it was back to the 125v B+ and dead.

I've verified the Q708 and Z705 regulation by swapping them into the working chassis. Q708 is getting pretty damn hot while running. Not sure if it should.

I might swap U701 next...
 
Q 701 is part of the circuit that drives the 12 vdc which in turn drives the horizontal circuit....so it makes sense that if it is hot you have a problem keeping the B+ running at it's proper 117vdc. I've had that R 718 (supposed to be 10k) go bad and maybe one other resistor in that area keep me from getting 12VDC on pin 10 of U 701. Check your voltage at pin 10 on this IC and you'll probably not getting a good 12 volts there.
 
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