"Alex" bravely wrote to "All" (20 Jan 06 09:26:08)
--- on the heady topic of " Wobbly vertical edges on iiyama Vision Master
crt monitor"

Al From: Alex
Al Xref: core-easynews sci.electronics.repair:355909

Al Asimov wrote:

"Alex" bravely wrote to "All" (19 Jan 06 17:02:31)
--- on the heady topic of "Wobbly vertical edges on iiyama Vision
Master crt
monitor"

From: Alex
Xref: core-easynews sci.electronics.repair:355796

Hello all,

I have an iiyama Vision Master Pro 512 (HA202-DT) 22" crt
monitor. The image is distorted, giving wobbly vertical edges.
The distortion is not static, but is continuously moving,
resulting in an unstable picture.

Does it move smoothly up/down or jerking about at random?

Al It look as a random vibration in the horizontal direction. (Amplitude
Al ca. 0.5 - 1 mm)

Al Additional info: after letting the monitor cool down overnight the
Al picture is rock stable for a few minutes. As the monitor warms up, the
Al distortion increases.

Al So would I be looking for overheating components, or still for a
Al faulty capacitor?


Nope, if it is random horizontal it is likely arcing in the high
voltage, likely on or near the flyback. The warming up period is
simply the carbon track becoming more conductive with temperature.
Take a sniff around the back air openings when it is jittery, if it
smells acrid like electricty then that confirms it. You might even
catch a sight of the arcing with the cover removed in a dark room,
depending on how well shielded the flyback area is. A pocket AM radio
tuned between stations, brought around the back cover should also pick
up the static-like sound caused by the arcing.

What needs to be found is why it is arcing. One cause is an open peak
control network, off the horizontal output. This is often a small 2KV
capacitor with perhaps a resistor in series. If either one burns up,
the flyback pulse develops a narrow peak which has a higher than
normal voltage. Often the output transistor would breakdown and short
out but it seems this one can stand a much higher voltage.

Another cause would be a sync digital processing fault but less
likely. Good luck!

A*s*i*m*o*v

.... A fail-safe circuit will destroy others.