Re: Magnavox FP5230 repair

In article <DLTAf.30586$SD1.9794@xxxxxxxxxxxxxxxxxxxx>,
rockobonaparte@xxxxxxxxxxx says...
> The original owners had the television inspected, and they were told
> "the board" is fried, due to the voltage regulator attached to it.
> They were told this is somewhat common for that model.

Sounds like "module jockeys". I wouldn't put much faith in that
information.

> What I have done so far is hooked up an external input. I managed to
> get audio out of it, but no video at all. Nothing comes up when I push
> the "menu" button. So it looks like I'm not getting anything on the
> screen at all.

If you get sound, the "regulator" is probably fine.

> I'm assuming "the board" is the "video processor board" that I see
> coming up on google.

More likely the large signal board (LSB), which has the power
and deflection circuits.

Unlike small TV's that most of us are accustomed to, the horizontal
deflection and high voltage circuits are separate. These sets also
have protection circuits that shut down high voltage or blank video
if they sense any number of error conditions like loss of scan,
excessive beam current, etc.

Having said that:
If the tube filaments light, you have horizontal deflection.
The buzzing you hear is probably vertical deflection.

A bad thing happened on some of these sets if connected to, say, a
VCR that goes to blue screen due to loss of signal. Blue tube after
being driven 100% for awhile gets so hot that it will actually crack
and lose vacuum. Sometimes you can see the crack through the lens,
sometimes it drips onto the LSB, which burns things up, but in either
case the blue tube now draws excessive beam current which shuts down
high voltage. Usually throw away when this happens.

If that hasn't happened, a common electrical failure is for the high
voltage transformer T900 to break down, which causes the HVOT transistor
Q906 to overheat and short out, which blows open 0.33 Ohm fusible
resistor R934. R934 is hidden in front of the heat sink on the right
front of the board. It's not easy to get at, but easy to test once you
do. If open, it usually means T900 and Q906 are both bad. Couple hun
to fix, but usually worth it.

If not one of the above, check back for more ideas.
.

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