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Magnavox Standby Transformer Testing

Hi I am new to Google Groups and this is my first post.

I have a Magnavox RM8341 projection TV. The tv does not power up and I believe the problem is with the standby power. The TV has a very small dc standby transformer.

Its kind of hard to describe ,but it here it goes.

The primary has 5 pins. The ground is in the middle (3rd pin). On both sides of the ground there are a pair of pins being the power input.

The secondary has 3 pins. The ground is on the end of the transformer. And the output are together.

My questions is exactly how do I test this transformer?

Can someone give me more specs on the transformer?

Here are two links for images of the transformer:

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THANKS FOR ANY HELP!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Reply to
media3d
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Would be nice if you could get your hands on some service literature. Have you tried that? Unless someone here in SCR has dealt with this identical chassis and remembers the test voltages (assuming this is even the problem), asking for the specs is just a crap shoot at best.

Reply to
Meat Plow

I have a service paper that came with the TV but its no help at all. All it says from my understanding is that 12V enters the primary and the next test point after the secondary indicates 9V.

Reply to
media3d

Transformers are a black hole in repairing, if you can find the service manual you could have the directions for checking ohms at the coils. Otherwise you must unsolder it and just check the continuity of the coils.

Good luck

Pixel

Reply to
gianluca.tovo

Hmmm, I think I would look into the proper service literature. Unless there was some manufacturer defect in the transformer, it's unlikely it could fail from another issue within the supply.

Reply to
Meat Plow

Thanks for th help I have removed the transformer from the board and tested for continuity and I get a good reading for both primary windings and the single secondary winding.

Could the problem be bad solder connections because someone had the same problem with a standby transformer and it ended up being bad solder connections.

I don't mean to be rude but does anyone have a copy of this TV's service manual.

Thanks again for all of those that helped. THANK YOU

Reply to
media3d

Like almost everything else in these sets, the standby supply is switch mode. It should be running all the time, check for 9V at TP12. If not, the problem is usually back on the hot side.

It's unusual for the transformer to be bad, but FYI pins 4 and

5 are the 177V primary winding, 1 and 2 are the 12V hot side supply, pins 7 and 9 are the cold side 9V output.

A common failure is for R416 to open up. This is a 56K 1W resistor that provides bootstrap voltage to start the standby regulator when the set is first plugged in. IC401, the hot side controller, has also been known to go belly-up for no particular apparent reason, and of course the associated drive and feedback parts can cause problems.

Yes I have the schematic and can maybe coax my old scanner to work if you need it.

Reply to
Bill S.

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Reply to
Bill S.

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