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Viewsonic PS790, no H sweep

This Model VCDTS21420 Chassis 19VS002 VGA monitor has HV and the CRT fils are lit, but there is no H sweep, just a vertical line if G2 is turned up. Q550 (yoke drive?) checks OK but has no B+ on it. Where does the sweep circuit get it's source voltage? So far, I found bad crimp connections (I soldered them) on the 2 pin plug of a coil that's wired in series with the yoke and sits on top of it. I suspect the intermittant plug pins caused the sweep failure and that it's a common problem in this model. A web search didn't help much. Can you? Thanks in advance!

Ray Carlsen A/V Engineering University of Washington, Seattle

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From post at above forum "The couple I've seen have bad solder, combined with blown Horz drive transistor Q550, FET Q881, and .8amp microfuse Q876. Symptom is a vertical line up the centre of the screen."

Wayne

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Wayne

Wayne, Thanks for the response! The FET is shorted and the fuse open but the sweep driver transistor Q550 appears to be OK in my monitor. I'm hunting down a replacement for the FET. Nobody has yet mentioned what actually creates the failure, namely two intermittant connector pins on the plug at board location J127, right next to the yoke plug. If the connections are not fixed (solder instead of crimp), the new parts will fail again.

Ray

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