Re: Sharp LL- T17A4-B lcd Monitor
- From: jakdedert <jakdedert@xxxxxxxxxxxxx>
- Date: Sat, 14 Jun 2008 23:20:13 -0500
hr(bob) hofmann@xxxxxxx wrote:
On Jun 14, 12:42 pm, jakdedert <jakded...@xxxxxxxxxxxxx> wrote:jakdedert wrote:jakdedert wrote:Has this one gotten everyone as stumped as it has me?Bought from the 'E' place for cheap. Reported symptom: video comes onSo far, no luck. ESRd all caps on video board. All good. Bad news is
and fades out. Figured it was high ESR smps caps.
Actual symptom: backlight comes on, image consist of random horizontal
lines, which eventually--after some intermittent vertical
scrolling--settle into a very nice image. Takes like two minutes to
warm up. Shutting the monitor down for some unknown time starts the
process all over again. Continuous viewing yields a stable image with
good resolution, brightness and linearity. Shutting down for short
periods is not problematic.
There is only one HV (100 @ 400v) cap in the ps. ESR is .46, which I
assume is within tolerance. Other caps in the ps also seem fine.
This presents so like a classic cap issue (needs to warm up), that I'm
going to next pull the video board and check caps there...possibly get
some freeze spray and see if I can duplicate symptoms that way.
Reality check: any problem with the above procedure, or experience
with this particular monitor? Any suggestions as to where to go if
the above doesn't produce a dx and fix?
Thanks as always,
jak
that monitor rarely straightens up anymore. I got it to display
correctly only once this evening, so no chance of trying to reproduce
symptom via freezing components. Power supply voltages appear nominal
and clean. No effect from flexing components. Reseated all cables on
the video board.....
It looks like the horizonal rows are not being addressed, as the current
display is a series of fine vertical lines of whatever color is
predominant in that area of the display. Still some strange horizontal
scrolling effects when first powered, but they only last a few
seconds...two or three horizontal bars scroll down the screen, then
disappear.
Any help here? Is this toast [beyond my ability to fix...]? My scope
(20 mHz) is not fast enough to look at the video timing....
jak
After three days of occasional attention, the symptoms still present as
before. I occasionally see the beginnings of a legible image, with bits
of recognizable video scrolling down the screen. Usually these break
back up into a screen full of vertical lines again; but occasionally
I'll get an 'almost' image first.
Some help, even if it's just commiseration, would be appreciated. So
far, not a single reply.....
jak- Hide quoted text -
- Show quoted text -
With a fixed video input signal, you should be able to figure out what
signals should be present on the leads to the LCD. A giant X painted
on a board and captured with a camcorder or regular point and shoot
camera connected to the video input of the monitor whould give you a
starting point. Do you have a schematic?
That's an interesting concept. No, I don't have a schematic; but pulled up another Sharp lcd service manual on the web hoping it was similar.
No such luck, but some of the diagnostic procedures spec'd a higher bandwidth scope than mine...which I use mostly for audio bench work.
Thanks,
jak
.
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