Lg 60PK550 Problem

[fireproof710]

Re: Lg 60PK550 Problem

Any further conclusions about that mystery capacitor?

[freakaftr8]

Re: Lg 60PK550 Problem

Im still lost on it. 1800v seems rather odd for a capacitor in a SMPS. Im more thinking that 1.8KHP is a 10% tolerance notation. But the 223H may in fact be .022uf

Someone else needs to chime in on this one. A well known supplier of components buddy of mine is even lost on what that cap means...

[tom66]

Re: Lg 60PK550 Problem

I have heard of 1250V capacitors, it's not too much of a stretch to imagine a 1800V capacitor existing...

[fireproof710]

Re: Lg 60PK550 Problem

Would it be conceivable to consult a technical diagram of the power board to find the specs? We have a betacam deck at work from back in the day that came with a hefty manual that diagramed every board in detail. Would a similar document exist for a tv?

[fireproof710]

Re: Lg 60PK550 Problem

I had somebody tell me it was a 22uf 1800v. I emailed a few component supply places and asked if they could help ID it.

[fireproof710]

Re: Lg 60PK550 Problem

Digi-Key got back to me. They too think its a .022uf 1800v. They said the closest thing they had was a 2000v, but its leads are probably too short to install in the same location. Would installing a cap with a higher voltage rating screw everything up?

http://www.digikey.com/product-detai...235-ND/1532455

Waiting to hear back from Mouser and Jameco.

[tom66]

Re: Lg 60PK550 Problem

Higher voltage rating will be fine. You could break the leads off a resistor and solder them to the leads of that capacitor as replacements.

[fireproof710]

Re: Lg 60PK550 Problem

Cool, I'll give that one a try. In summary, I will be ordering/replacing:

1) The suspected faulty mosfet and the one next to it that is the same type.

2)The high voltage mylar cap.

3)The small caps near the heat sink and all of the other small caps on the board while I'm at it.

Before I place the order, is there anything else I should consider replacing?

[fireproof710]

Re: Lg 60PK550 Problem

Do the mosfets need thermal paste on them for contact with the heat sink? If so any recommendations?

[tom66]

Re: Lg 60PK550 Problem

Yes. Generic thermal paste hasn't failed me yet.

You should also replace the IC which drives those FETs, if there is one on that board, otherwise, they may fail immediately on power up. Picture of underside of board near FETs?

Consider building a lightbulb test jig: https://www.badcaps.net/forum/showthread.php?t=32748

[fireproof710]

Re: Lg 60PK550 Problem

I'll snap a pic of the underside when I get home. What exactly is an IC?

[tom66]

Re: Lg 60PK550 Problem

Integrated circuit -- will be in charge of driving the MOSFETs.

[fireproof710]

Re: Lg 60PK550 Problem

Ah, makes sense. I'll report back once I'm home and get a pic.

[fireproof710]

Re: Lg 60PK550 Problem

This is the nearest IC. All of them are pretty dang small and are all soldered straight to the board. I'd have to get a hefty magnifying glass to read the markings on it.

[tom66]

Re: Lg 60PK550 Problem

That would be a suspect, I would advise replacing it.

[fireproof710]

Re: Lg 60PK550 Problem

Okay. I'll order the other parts so I can get some soldering practice in. God knows I'll need it for those leads on the IC. I'll report back once I've gotten a magnifying glass I can use to read the markings on the IC.

[fireproof710]

Re: Lg 60PK550 Problem

Okay. Got the parts. Swapped them out. Still works intermittently. Still makes clicking noise (though more static/click hybrid sounding) from the same area. I got a loupe and looked at the numbers on the IC. It looks to be an "ST" brand circuit There are two rows of markings one at the top that I could faintly and not concretely make out as "L6591AU"
The other string of characters is below and to the right of the ST logo and is indecipherable. Nothing comes up in google for the numbers that I think are stamped on there. I'm wondering if I should just get a new board at this point. I found one on ebay here:

http://www.ebay.com/itm/LG-POWER-SUP...p2054897.l4275

It looks to be the same numbers except my PCB number is: EAX61432501/6
and the one on ebay is EAX61432501/10

Thoughts?

[fireproof710]

Re: Lg 60PK550 Problem

I found another one cheaper and with the exact number match. I think I'm going to go for it.

[tom66]

Re: Lg 60PK550 Problem

Missed your post, but L6591 is probably the part #. Did you replace that chip yet? It can be difficult, but if you can remove it, then you can put it back on. No harm trying if you're going to get a new board anyway.

[fireproof710]

Re: Lg 60PK550 Problem

Thanks for the reply. Googling L6591AU returned no results but leaving off the "AU" gave me what appears to be an AC/DC circuit with the same number of pins as the one on my board.

http://www.digikey.com/product-detai...art_dkc_buynow

I'll give it a go.