jayc

I have a JVC AV-20CM5 that has a horizontal line in the middle. Some have described this as a "white line" but in my case it shows color, motion, etc. of what is happening on TV. But, of course, it's just a few pixels tall.

The person here with the exact same model had the same problem: http://experts.about.com/q/1749/3380300.htm

The reply was:

"The vertical IC is shorted. Replace it and check the resistor and diode that supply B+ to it."

Do you think the person is correct? If so, how difficult do you think this repair would be without any previous TV repair expierence?

The FAQ here ( http://repairfaq.ece.drexel.edu/sam/tvfaq.htm ) looks very detailed which I plan on reading if I decide to give it a shot. Might as well if the TV will otherwise go to a landfill (which I'd rather not do).

Thanks!

[Edited to correct direction.]

TheOne

If you have a vertical line, it indicates that there is vertical scanning and no horizontal scan. The fact that there is a line shows that the line stage is partly functioning as far as supplying the EHT voltage. I would look for a open circuit (bad connector, plug etc.) to the horizontal scan coils from the line stage.

__________________
\"You can\'t make a circuit fool-proof, cause fools are so ingenious!\"

jayc

Oops! I meant horizontal line, sorry.

I also forgot to mention that banging on it (I know... ignorant man's first tool) used to fix it some of the time. Now that tool doesn't work so well.

TheOne

Ok then the previous advice you mentioned seems in order.

__________________
\"You can\'t make a circuit fool-proof, cause fools are so ingenious!\"

panic mode

actually problem you describe is quite common. it is usually to be
traced to poor connection which might might be further eroded
by arcing and that's why you cannot reproduce it. this also happens
due thermal problems if chip overheats but in this case banging is
unlikely to help. i suggest resoldering all connections on and around
vertical osc. and cleaning contacts on the yoke connector.
vertical osc/driver is usually single chip so it should be easy to
replace. it might have gone by now after long strugle with arcing load.
power for vertical circut is normally derived from coil/tap on the high
voltage transformer used in the end stage of horizontal circuit.
i've seen such problems (loose connection or cracked PCB) near
the transformer. same suggestion as above - inspect for cracks,
check continuity and resolder.
make sure to give some time to capacitors to discharge before
getting inside tv. if you get it to work even briefly - great, this is
time to start some testing. normally in such case one would use
cold spray to freeze parts of the circuit. cold makes things shrink so
if the problem is not cured it will be easily found by applying directed
jet of cold gas from the spray can. be careful since this can only
yield results if performed on running equipment so don't go crazy,
don't make spils, don't toch much etc.
sometimes i had to use heatgun first to get to working condition
before using freezing spray to pinpoint problem.
again, all this thermal stress is not too good so use it carefuly, don't
blow heat on heatsinks (should be obvious...).
i would suggest hair dryer instead of real heatgun (much lower
chance of damaging something).