Question about Sharp LC-46D85UN Power Supply

[kevinm34232]

After opening TV, when plugging TV in a saw a part burning which turned out to be C7816 which goes across pins of D7806. I removed this burnt cap (it actually crumbled into dust), which I believe looked similar to the caps in the last pic.
Since I cannot identify it, does anyone have a schematic for this board, or can tell me if it is even necessary. The TV turns on now that the burnt cap was removed. Thank you.

[tom66]

Re: Question about Sharp LC-46D85UN Power Supply

It is the snubber for the diode. Without it, the diode will fail early due to higher peak voltages.

[kevinm34232]

Re: Question about Sharp LC-46D85UN Power Supply

Is there a way I can determine the right specs for it?

Diode is a STTH8R06FP
https://cdn.badcaps-static.com/pdfs/...2456fa105e.pdf

[kevinm34232]

Re: Question about Sharp LC-46D85UN Power Supply

Found some info on another site, replacing C7816 with
part # 561R10TCCT22 (Ceramic Disc Capacitors 1Kvolts 220pF 5%)

Hope this helps someone in the future.

[budm]

Re: Question about Sharp LC-46D85UN Power Supply

Found some info on another site, replacing C7816 with
part # 561R10TCCT22 (Ceramic Disc Capacitors 1Kvolts 220pF 5%)

Hope this helps someone in the future.

That is the snubber cap which has the same failure mode as in many Samsung power supplies board.
Good fix.

[kevinm34232]

Re: Question about Sharp LC-46D85UN Power Supply

It was completely burned to a crisp. I had an older Samsung with the same problem a while ago. I replaced with the best cap I could find.

[tom66]

Re: Question about Sharp LC-46D85UN Power Supply

I would use higher than 1kV rated as the cap may have failed due to low rating (maybe peak transients exceeding 1kV?)

[kevinm34232]

Re: Question about Sharp LC-46D85UN Power Supply

The part I ordered for replacement is this:

http://www.mouser.com/ProductDetail/...W5sIx2JA%3d%3d

This one is huge, did they send me the right part?

[tom66]

Re: Question about Sharp LC-46D85UN Power Supply

Lead Spacing: 9.5mm
What do you think?

[fzabkar]

Re: Question about Sharp LC-46D85UN Power Supply

I'm still downloading it (67MB !!!) but the following service manual has the same capacitor and diode circuit references:

[kevinm34232]

Re: Question about Sharp LC-46D85UN Power Supply

What is the difference in this part compared to the one I ordered, besides the size?

[kevinm34232]

Re: Question about Sharp LC-46D85UN Power Supply

I was looking towards the bottom where it said width 4mm.

[fzabkar]

Re: Question about Sharp LC-46D85UN Power Supply

I would use higher than 1kV rated as the cap may have failed due to low rating (maybe peak transients exceeding 1kV?)

I haven't seen the circuit, but if the capacitor is directly across the diode, then its rating should be related to the diode's own VRRM spec, which is 600V. Therefore ISTM that the capacitor's 1kV rating should be ample, and that a spike should kill the diode before the capacitor.

[tom66]

Re: Question about Sharp LC-46D85UN Power Supply

That's probably the thickness of the device.

[kevinm34232]

Re: Question about Sharp LC-46D85UN Power Supply

So this part will work then?

[tom66]

Re: Question about Sharp LC-46D85UN Power Supply

I haven't seen the circuit, but if the capacitor is directly across the diode, then its rating should be related to the diode's own VRRM spec, which is 600V. Therefore ISTM that the capacitor's 1kV rating should be ample, and that a spike should kill the diode before the capacitor.

Most likely. Although the rating of many types of capacitors has to be derated if the slew rate is very high. But yes, in theory, 600V should be ok, a higher rating will not hurt.

[fzabkar]

Re: Question about Sharp LC-46D85UN Power Supply

Most likely. Although the rating of many types of capacitors has to be derated if the slew rate is very high. But yes, in theory, 600V should be ok, a higher rating will not hurt.

I'm not suggesting that there is anything wrong with a higher rating. In fact it is preferable. All I'm saying is that 1kV should be more than enough, allowing for derating factors, as you have said.

[fzabkar]

Re: Question about Sharp LC-46D85UN Power Supply

FWIW, here is the APFC section from a different Sharp model:

[cprem]

Re: Question about Sharp LC-46D85UN Power Supply

Did replacing C7816 fix the problem of set having no power?