Westinghouse SK-32H540S "2 seconds to black" Darfon

[high-tech]

I found a transformer with shorted secondary and replaced with new, and the TV still shuts the backlight off after a couple seconds and it trys a second time but still no good. I checked the N channel mosfets feeding the primary side of the inverter transformers and they are good. I don't have a schematic for this board and wish I could find one...

Im hoping somebody here knows this problem inside out

im getting the necessary voltages on the ps_on and bl_on pins on the power supply board connector

[retiredcaps]

Re: Westinghouse SK-32H540S "2 seconds to black" Darfon

I found a transformer with shorted secondary and replaced with new,

I'm used to seeing the secondary transformer pins go open circuit, not shorted.

See

http://www.lcdparts.net/TransformerD...ProductID=2775

Measure the resistance between S1-S2 and S3-S4. Both readings should be within 3% of each other on all your transformers.

[budm]

Re: Westinghouse SK-32H540S "2 seconds to black" Darfon

Was one of the transformer burnt out so bad that it has big hole on the board?
How are those small ballast blue caps by the outputs of the transformer? Any of them has any resistance reading, specially the ones by the new transformer you put that has burnt hole on the board.

[high-tech]

Re: Westinghouse SK-32H540S "2 seconds to black" Darfon

I'm used to seeing the secondary transformer pins go open circuit, not shorted.

See

http://www.lcdparts.net/TransformerD...ProductID=2775

Measure the resistance between S1-S2 and S3-S4. Both readings should be within 3% of each other on all your transformers.

Im sorry, the Xformer did open up and the other 2 xformers all measure right at 1.8k on Secondary pins, thanks for your feedback, I'm not sure what to do next. Im not familiar with the control circuit for this inverter.

[high-tech]

Re: Westinghouse SK-32H540S "2 seconds to black" Darfon

Was one of the transformer burnt out so bad that it has big hole on the board?
How are those small ballast blue caps by the outputs of the transformer? Any of them has any resistance reading, specially the ones by the new transformer you put that has burnt hole on the board.

The board was burnt bad enough to eventually cause the secondary high voltage to leak so I decided to carve the hole out a little bigger to remove the semiconductive material left behind by the burnt xformer.

All the blue caps check ok, they all read open on the highest resistance scale on my meter.

[budm]

Re: Westinghouse SK-32H540S "2 seconds to black" Darfon

Well, you did that correctly to carve out the carbonized section of the board. The possibility still can be the driving circuits or can be bad lamps.

[high-tech]

Re: Westinghouse SK-32H540S "2 seconds to black" Darfon

Well, you did that correctly to carve out the carbonized section of the board. The possibility still can be the driving circuits or can be bad lamps.

I used a set of test lamps and they all light up for 2 seconds and go off again so my bulbs are ok im pretty sure.

[budm]

Re: Westinghouse SK-32H540S "2 seconds to black" Darfon

You are in the same boat as this one:
https://www.badcaps.net/forum/showthread.php?t=21240

[high-tech]

Re: Westinghouse SK-32H540S "2 seconds to black" Darfon

Just for giggles I measured the voltage at the main filter caps after the rectifier and I got 161 volts dc with the set turned off. While the inverter is on I got 148 volts, a 13 volt drop.

I think it should be up around 167 vdc off and im not really sure what the normal load is