Help: Toshiba TV CM905C Vertical Fold Over

[Wally Chopyk]

I have an old Toshiba TV, model CM905C, with vertical fold over at the
top during warm-up only. The top of the screen has 6-8 lines fold over,
that gradually creep up and disappear behind the mask 8-10 minutes after
power on. Turning the power off, waiting for a while, then on again,
starts the same process over. I have checked voltages from the AC power
supply to the horizontal and vertical sections and found them to be
stable during and after warm-up. I have bridged various electrolytics in
and around the horizontal and vertical sections with no affect or change
in symptoms. I do not have a circuit schematic, so would welcome any
suggestions on how to isolate the fault. The picture is otherwise great,
good colour, good contrast, good focus. My concern is that something is
about to breakdown and I would prefer to fix it now. Thanks in advance
for any suggestions.

Wally

 

[Sofie]

Wally Chopyk:
You are... or at least, were, on the right track. The culprit is probably
is one or several faulty, high ESR electrolytics near and around the
vertical deflection circuitry and output chip. Without an ESR test meter
you can not easily determine which electrolytics are faulty..... at most,
there are only a handful ( 6 to 8 ) of electrolytics in that area of the
circuitry so you would be best advised to just REPLACE them all..... don't
screw around bridging them or just guessing regarding individual
electrolytics..
Your concern about fixing it now and about something is about to breakdown
is absolutely correct. Immediately STOP using the television until you get
it fixed. As long as it is "limping along" the repair should be fairly
straightforward and economically feasible at most repair shops. If you
wait until further problems develop the repair cost can easily be much more.
If you are at a loss about how to continue the repair of this television you
might consider taking it to repair shop, for at the very least, a repair
cost estimate so you can make an intelligent repair decision with facts
instead of internet or telephone guesses. If you take it to the repair shop
AFTER aborted or failed home repair attempts the repair shop price could be
more expensive.