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
I'm sorry, my ESP transceiver is down at the moment. Or in other words,
could you please tell us the make/model. There isn't just one design you
know...
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.
OK. The second 2 symptoms (small, dim, horizontal) sounds like something
is loading horizontal output stange. That would reduce the EHT of course
(which would tend to enlarge the picture), but will also reduce the
deflection amplitude.
It's not unhard-of for the vertical output stage to take its power from
the flyback transformer. In which case a fault there (and I'd suspect a
shorted capacitor) would load the horizontal stage too.
Can you find the vertical output stage? Is there a TDA1170 IC (a good bet
in an older chassis), it may have a heatsink soldered to the tabs. Or can
you trace back the leads fro mthe yoke? 2 will go near the flyback
transformer, it's the other 2 you are interested in.
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.
Maybe the monitor is drawing more supply current when the fault occurs,
loading down the mains PSU too.
-tony