Viewsonic PS790, no H sweep

[Ray Carlsen]

Search the forum at http://www.network54.com/Forum/87612/ for PS790 and you
will get multiple hits. 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,
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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[Wayne]

On Tue, 06 Nov 2007 11:44:13 -0800, Ray Carlsen <rr0cc@my0uw.net>
wrote:

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

Search the forum at http://www.network54.com/Forum/87612/ for PS790
and you will get multiple hits.

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

 

[Ray Carlsen]

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

--

My return addy is spamblocked. To reply, remove the zeroes.