Build Your Own Arcade Controls Forum
Main => Monitor/Video Forum => Topic started by: jconstanza on December 04, 2008, 05:38:58 pm
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Working on a Wells Gardner K7500 that has the top half of the screen darker than the bottom. Tried swapping U601 (TDA1771) and U701 (LA7851), same thing. Am I looking in the right places?
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got a pic of the prob
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Here you go
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whats your input source to this?
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Well I have it on a wells pattern generator right now, but it came out of a Hydro Thunder
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the generator is giving this a 15khz signal?
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That's a weird one.
Just for giggles, check R101 and see if it's open.
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looks like a problem with the vertical sync or a frequency issue
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what happens when you adjust the vertical size?
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I had a similar problem with a K7000 that had half the screen darkened, but split vertically. Never got around to looking at it again. Interested in hearing your solution.
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15khz not sure? I have it set to EGA on the generator. R101 is not open. I use only my multimeter to troubleshoot. I do have an oscilliscope, but no clue on how to use it. Can I measure khz with my meter?
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well if the generator is set to ega/24khz then the signal is fine
the vertical hold or sync is the only thing i have ever seen cause this
do you have an option for sync polarity on the generator?
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I had a similar problem with a K7000 that had half the screen darkened, but split vertically. Never got around to looking at it again. Interested in hearing your solution.
Smoothing cap - 47uf, 160V @ C57.
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No, no option for that.
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C57?
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and you have the same problem in the cab?
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Yes
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well thats good(in a way) as it rules out frequency
have you followed the wg repair guide on this?
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Ehh, not completely. It's tough cause I don't have all the parts that they are pointing out
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C57?
That was a response to the guy who had the problem with his K7000.
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from wg guide
SCREEN BLACK ON ONE SIDE
BLACK WIRE ON FLYBACK REVERSED
C310, C812
i had a similar fault on a few polo monitor caused by a resistor on the g1 circuit.its equal on the k7500 is r545 150ohm
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Wow! I feel like an idiot. I got it like this from the customer. It had the wrong controller board.
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;D
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Wow! I feel like an idiot. I got it like this from the customer. It had the wrong controller board.
so much "fun" when someone has been in 'em.
recently had a serv call on an RCA projo. the hv splitter was arcing ( AND in the wrong place - HUH ??)
seems another "shop" had replaced the red crt , and didn't put the block back where it belonged,
misrouted ctl/spkrs lines and didn't reinstall a number of screws. ::)
hauled the chassis back to shop to undo all the damage ....
qrz