Samsung LN46D550 power board issue

[Malachi]

I picked this up today. The fuse by the power inlet is blow and so is the component CP820, assuming it's a capacitor.
Would replacing the fuse and cp820 fix it or is there most likely something else blown?
I will attach a pictures of the actual board and one from shopjimmy.

[Malachi]

Re: Samsung LN46D550 power board issue

Also I noticed that on the bottom side of the board, CM801 has one lead not soldered. Is that ok?

[diif]

Re: Samsung LN46D550 power board issue

Check DP802 for a short.

[Malachi]

Re: Samsung LN46D550 power board issue

Check DP802 for a short.

Excuse my ignorance. How exactly? Off the circuit board? Between the two legs?
It has a shorter leg between the two soldered ones.

[budm]

Re: Samsung LN46D550 power board issue

The burnt up cap is a snubber cap for the DIODE DP802, the cap is connected in parallel with DP802, so to check the DP802 you just use the two solder pads of cap CP820 (Removed) for testing DP802.
You should also check the resistance reading between the two legs of the main filter cap CP802, it should show low resistance at the beginning then the resistance should rise up as the cap is charged up by the meter, and of course no power to the board, report the result.

[Malachi]

Re: Samsung LN46D550 power board issue

The burnt up cap is a snubber cap for the DIODE DP802, the cap is connected in parallel with DP802, so to check the DP802 you just use the two solder pads of cap CP820 (Removed) for testing DP802.
You should also check the resistance reading between the two legs of the main filter cap CP802, it should show low resistance at the beginning then the resistance should rise up as the cap is charged up by the meter, and of course no power to the board, report the result.

DP802 is shorted then as I get no beep between the solder pads of CP820. I didn’t remove it as all that is left is the two legs sticking up out of the board.

Resistance on CP802 started at 44M ohms and dropped, if I did it correctly.

[budm]

Re: Samsung LN46D550 power board issue

DP802 is shorted then as I get no beep between the solder pads of CP820. I didn’t remove it as all that is left is the two legs sticking up out of the board.

Resistance on CP802 started at 44M ohms and dropped, if I did it correctly.

What mode did you set the meter to? Diode mode? Ohm mode?
Meter does not beep if it sees open circuit, you need to read your meter user manual.
Short your meter probes together and see what it does.

[Malachi]

Re: Samsung LN46D550 power board issue

When I touch my leads, the meter beeps. Now that I think about it that means it’s not shorted. Lol

[Malachi]

Re: Samsung LN46D550 power board issue

To read the cap, I set it to ohms, resistance.

[Malachi]

Re: Samsung LN46D550 power board issue

How would I find out the value of that snubber cap that blew since there is nothing left of it?

[budm]

Re: Samsung LN46D550 power board issue

220pf 2KV ceramic should be fine.

[Malachi]

Re: Samsung LN46D550 power board issue

Thanks budm.
These are ok?

[budm]

Re: Samsung LN46D550 power board issue

That should be good.

[Malachi]

Re: Samsung LN46D550 power board issue

Thanks. I had ordered them anyway.
Now as the fuse. It’s a
T 5A H 250V. I have some T 12A 250V from another set I fixed. I problem shouldn’t use the 12A in place of 5A. Right? Lol

I have to start saving boards for parts.

[Sk8dancer]

Re: Samsung LN46D550 power board issue

I found this thread particularly interesting because my mother-in-law's Samsung LN46D550 was not turning on. So I took the back off and replaced both fuses, which caused the stand-by light to blink 5 times when I turned the set on again. However, when I put the old fuse (with the purple line) back in FS8029, the set wouldn't come on. So I concluded that something on the power board had caused that fuse to blow.

After reading several posts on how to determine whether the power board was bad, I disconnected the main board, and found that the set would not turn on, and that no lights were coming out of the screw holes. So I then disconnected the T Con board and found the same thing.

I also noticed that the blue capacitor (cp820) on my board was bent over, and that the capacitor's legs, both above and below the board, were sloppily embedded in what I thought was a grey epoxy-like material. So I suspected that that capacitor was the problem, just as cp820 appears to have been in the OP's board.

I therefore PMed the OP and asked whether him whether he had solved the problem and if so, how. But he replied that he just couldn't remember how he solve it, or even if he had.

Anyway, as the TV was refurbished back in 2018 by a local repairman, I didn't think that the repair was still under warrantee. So, I emailed the attached picture to him and asked him if he would test the board and repair it for me — if I sent it to him, and the repair would be less than the app. $50 it would cost me to buy a used board on Ebay.

However, here's what he said:

“That grey silicone is from the factory. Contrary to what you read on the internet, capacitors rarely go bad. It is too difficult to repair a board like you are thinking because you need the main and sometimes other boards to trigger different voltages.”

Now, I don't have a great deal of knowledge about circuitry, but I've read enough in this forum and others to know that capacitors certainly do go bad. Moreover, I saw that the capacitor on the boards on Ebay were standing upright, and that none of them had silicon on them. So I have to suspect that the repairman was lying to me about both things for some reason.
I was therefore hoping that list-members would be kind enough to answer the following questions for me:

1) Is my suspicion that the repairman was lying to me warranted?

(2) Can a power board that was removed from a TV be tested without too much trouble?

(3) Does the blown fuse confirm that the power board is the problem?

(4) After I had changed the fuse, the first two times I plugged the power cord into the wall socket and then into the board – which I probably should have done in reverse -- the small transformer or voltage regulator TI805s (?), next to the label marked COLD) sparked. However, the set still came on, and the stand-by light blinked 5 times. Does this confirm that the power board is bad, and that I should replaced it, since I don't have the time, equipment or knowledge I'd need to repair it ?

Thanks very much for reading this post, as it ended up being a lot longer than I had anticipated, and thanks in advance any help anyone can give me on this.

Steve