D Yuniskis wrote:
Sylvia Else wrote:
D Yuniskis wrote:
Sylvia Else wrote:
I bought this on Ebay for $5.50 on the off chance that I could fix
it. It was described as having lost picture with a "pop", and with
the observation that a TV repairman said it sounded like it could be
a power supply issue.

I've determined that the sound works OK, as does the tuner and video
signal stage - it outputs the composite video on an AV out socket.

This is A Good Sign.

The diode *looks* OK. Though it seems like there
might be a wire or maybe some "glue fibers" draped
across it?

Presumably this diode shorted out. It's on a board close the EHT
circuitry.

I'd look at the switching transistor (HOT) first.

But what are the chances that that's all that's wrong with it? Just
getting the board out to gain access to the underside will be a
fairly major exercise.

grin You should see what a nuisance some of the high end
Sony monitors are (were?) to service! :

As far as I can see, and despite the numerous headers, it's impossible
to remove the circuit board from this TV without desoldering some
wires from it. I rather think it was never intended to be repaired.
However,

...like many *cars*! :-/

with some of the unpluggable wires unplugged, there is just enough
slack in the remainder to prop the circuit board up into a vertical
position.

Based on the described "pop" symptom, I was looking for something
showing physical trauma, but if there's any visible, I'm missing it,
and I've spent a good while looking.

I've established that the HT (190V) is present at the powersupply.

That's *mains* voltage (rectified and filtered?).

I'm in Australia, mains voltage 240V RMS.

Are you
sure the flyback is working?

At this stage, I'm reasonably sure that it's not, but due to a lack of
appropriate input signals.

I'm somewhat aghast at the sheer complexity of the board that's creating
the horizontal and vertical scanning outputs, and the anode voltage.

It has two LSI circuits, including one that contains a programmable
processor, and no less than six transformers (I don't think any are
chokes, but don't quote me), not including the EHT transformer.

OK, so it's implementing the functions of a multi-sync monitor (the set
has an XVGA input), but even so....

Whatever happened to circuits that just contained a couple of valves?

Sylvia.