"Arto Rantala" bravely wrote to "All" (19 Mar 05 11:59:02)
--- on the heady topic of " Hitachi CM813ET image jitter"

AR From: "Arto Rantala"
AR Xref: aeinews sci.electronics.repair:43408

AR Thank you for your replies, Asimov and Jerry,

You discussed vibration as not affecting the problem but many devices
may have heat sensitive internal joints which are not very sensitive
to vibration by comparision to cold solder joints. Among these are
electrolytic caps, resistors, transistors, IC's, etc.
AR True. My intention is to at some point open the case and use cold
AR spray to find any such heat sensitive components. There are, however,
AR a lot of components in a monitor, making it rather difficult to just
AR start spraying around, which is why I would have been interested in
AR learning of any starting spots anyone could suggest.

Basically this symptom mimics what arcing would do, which is to inject
high voltage glitches into the horizontal output section. Other
circuits that handle high voltages are the focus and screen controls.
If one of these has an intermittant contact it would seem like arcing
too. Same thing with the neck board crt socket since this carries the
actual voltages to the tube and any intermittant here would also seem
like arcing. Clean the crt pins with a plastic scotchbrite pad.
Similarly the wire connectors on the main board for these voltages may
be iffy. Even the crt high voltage cup is a suspect, clean and use
dielectric grease to seal the air out of the high voltage rubber boot.
Don't forget to discharge the crt first just in case!

Check the solder joints at the HOT and especially the base drive.
Check specifically any small pulse shaping inductors in the base drive
for signs of glue in the legs. Remove old solder clean inductor legs
and pcb holes thoroughly and re-install with fresh solder.

If the yoke socket pins have shiny solder and generally looks good,
not dull grey, then I would definitely suspect electrolytic capacitors
next due to the age of the monitor alone. Replace those in areas close
to sources of heat such as heatsinks or power transistors. Replace
those which handle substantial power such as derived supplies. Suspect
anything that looks off colour or bulging, leaking, etc. After the
electros are tested for esr/value/leakage or replaced then proceed
next with testing zener diodes used for reference. Prod suspect parts
with a long plastic wand to provoke the symptoms. Use freeze spray,
etc.

There aren't that many small components in the horizontal output
section that each can't be replaced until the bad one is found.
There is a finite limit of parts after all.

A*s*i*m*o*v

.... :) What does that wire do? =3d8Q (oh!)