10 Jul
2006
10 Jul
'06
10:04 a.m.
From: "Jules Richardson" <julesrichardsonuk at yahoo.co.uk>
I'm asking this here as I've heard of it happening on all sorts of systems
before, as though it's a common fault and possibly with a common cause...
I've got a mono fixed-frequency display that'll often power up and display
fine for a few seconds, after which the vertical collapses and the
horizontal
shrinks slightly, such that the picture vanishes to a
single (squashed)
horizontal line in the middle of the screen. The "picture" goes rather dim
at
the same time.
I would have thought that was a power supply problem of some description -
except that some initial checks show that the expected single +12V supply
for
the display is at +11.8V, so only slightly down on
what it should be.
Hmm, I suppose I could try feeding +12V in from a bench supply and rule
that
one out...
Jules,
I start with any electrolytics you can find in the frame stage........
Does the monitor have seperate synch, or is it combined with the video?
Don't run it for long with the frames collapsed, or you will get screen
burn - if you need to run it for tests, keep contrsat and brilliance at a
minimum. The dimming of the picture may be a crude protection circuit that
reduces brilliance on loss of synch (to prevent screen burn).
Jim.