LC-37D43U Sharp LCD, No power No standby lights

[tom66]

Re: LC-37D43U Sharp LCD, No power No standby lights

Found this on 'net:-

Dead - no standby:
Replace zener diode D7907. Diode is in the standby 5V primary side of the power supply. Zener is 150 volt 5 watt.

[Glitcher]

Re: LC-37D43U Sharp LCD, No power No standby lights

Ok, its rated 47uf at 50v. Doesn't seem to look bulged. Luckily using my new ESR meter I'm getting a measurement of 47.84uf and ESR = 0.18 ohms.

[tom66]

Re: LC-37D43U Sharp LCD, No power No standby lights

See above. That cap is probably not the cause.

[Glitcher]

Re: LC-37D43U Sharp LCD, No power No standby lights

Found it! D7907 I pulled it out of the circuit and took its measurement.

Its labeled:
PK
IN
5383B
0652

Using the Diode setting, I'm getting 72 ohms in both directions.

[budm]

Re: LC-37D43U Sharp LCD, No power No standby lights

That is the Snubber Diode to protect the 5V STBY SMPS IC, hopefully the IC is not damaged. You should take the resistance reading of that 7-pin SMPS IC between pirmary ground and all the pins.
Sharp uses a lot of this power supply setup.
http://s807.photobucket.com/user/bud...27804087715754

[tom66]

Re: LC-37D43U Sharp LCD, No power No standby lights

Replacement:
http://www.digikey.com/product-detai...GOS-ND/1474183

[Glitcher]

Re: LC-37D43U Sharp LCD, No power No standby lights

Nice photos budm! Were you able to repair it by replacing the diode?
I took some measurements of the 7 pin IC (with the bad diode still removed out of the circuit). Using black probe on the negative pin of the large capacitor as primary ground (from photo in post #2) and red probe on each of the pins.

I'm getting 0.04 ohms on the circled pins, and the other pins I'm getting a "1" i think out of range for my meter on the highest setting of 2M.

I just made the order for the diode. I'll let you guys know how it goes when I replace it. Thanks!

[tom66]

Re: LC-37D43U Sharp LCD, No power No standby lights

You can see those pins are connected by copper so they should appear shorted.
Test that island (isolated) pin to one of the ones you have highlighted.

[Glitcher]

Re: LC-37D43U Sharp LCD, No power No standby lights

which one is the island pin?

[tom66]

Re: LC-37D43U Sharp LCD, No power No standby lights

Bottom left on this image -- it's isolated from the rest.
https://www.badcaps.net/forum/attach...6&d=1364837410

[Glitcher]

Re: LC-37D43U Sharp LCD, No power No standby lights

Ohh okay. Measuring that isolated pin and one of the ones i circled, I'm getting an out of range "1" reading on all my range settings except the diode setting.

If I use the diode function setting "2K" I'm getting 546 ohms in one way and "1" out of range in the other direction.

[tom66]

Re: LC-37D43U Sharp LCD, No power No standby lights

It's good, then.

[Glitcher]

Re: LC-37D43U Sharp LCD, No power No standby lights

Well that's good news to hear! Well just have to replace the diode and see what happens

[tom66]

Re: LC-37D43U Sharp LCD, No power No standby lights

Remember to let us know if it works!

[Glitcher]

Re: LC-37D43U Sharp LCD, No power No standby lights

Will do! Just wondering tom, where did you find the information about the psu and diode?

[tom66]

Re: LC-37D43U Sharp LCD, No power No standby lights

Forget... I just googled the model number and it was on one of these "ask the expert" sites.

[Glitcher]

Re: LC-37D43U Sharp LCD, No power No standby lights

Just replaced the diode today, and the TV is back to life!

Thanks for all the help guys!

[tom66]

Re: LC-37D43U Sharp LCD, No power No standby lights

Nice one!

[budm]

Re: LC-37D43U Sharp LCD, No power No standby lights

Thanks for posting back the repair progress.

[Baileybum1234]

Re: LC-37D43U Sharp LCD, No power No standby lights

exellent