Lg 60PK550 Problem

[fireproof710]

Re: Lg 60PK550 Problem

Ordered. Thanks for walking me through this. I see the light at the end of the tunnel

[fireproof710]

Re: Lg 60PK550 Problem

As an aside, I'm simply stunned that just about any component on these boards can be readily ordered on a handful of suppliers. The overall catalog numbers at these places must be overwhelming.

[freakaftr8]

Re: Lg 60PK550 Problem

okay here's the deal when you heat up that Mosfet if it's only a 3 pin that's not a voltage regulator on the power supply that's a MOSFET and when you heat it up you're changing the value that called RDS on and what that is is a certain window that is built into the mosfet that that has a value that when it hits at threshold its turned on that must be that is either out of sync or tolerance from its original value or the driver circuit that operates the mosfet like tom66 had mentioned is faulty so it's looking for a different value than that much that yet essentially either the capacitors in the circuit the MOSFET itself or the driver circuit is fault and if you're going to go about that route its all these components you're probably cheaper just to buy a power supply

[fireproof710]

Re: Lg 60PK550 Problem

Yeah, like i mentioned before, this behemoth of a tv has been sitting on my dining room table for about a month and I need to get it back on the wall asap. I'll try swapping out that IC. I have already done all of the small caps on the board including the ones directly adjacent to that particular power circuit. Like tom66 said its only a couple of bucks more, so its worth a try to swap out the IC. If that doesn't work, then I'll just buy a replacement board and be done with it. My power board is out of stock at Shopjimmy but I may be able to find one elsewhere. What I'm attempting to learn at the moment is if the number after the slash in the EAX number is a revision number and if I can use a different revision board with my tv.

For instance my tv's EAX number is EAX61432501/6. I have found boards whose numbers are EAX61432501/8 EAX61432501/9 and EAX61432501/10. So I believe they are the same board number, just different revisions. I contacted someone at ShopJimmy to inquire about compatibility between revisions as they seem to have a good handle on which boards are acceptable replacements. If it is indeed acceptable to use a board with a different number after the slash then I'll just go for that. They seem to be priced at $130-180 which is a bit more than I'd like to shell out in case it still doesn't solve the problem, but I feel pretty confident that the fault lies in the power board.

[tom66]

Re: Lg 60PK550 Problem

If the boards all have same pin connections and all screw holes same, and both for 60", it should work just fine. Verify with shopjimmy pics.

[fireproof710]

Re: Lg 60PK550 Problem

A tech from ShopJimmy replied very eloquently: "rev number should work" after having been asked about differing numbers. The page for my part says that the same board is useable on several different size tvs so it would seem as long as the EAY# is the same and the EAX# is the same (allowing for a different revision) it should be a good fit.

[Allan Woods]

Re: Lg 60PK550 Problem

Hi Fireproof and friends!

I found this amazing thread in a Google search because as it turns out, I have an LG 60PK550 with the exact same symptoms as yours. I have been reading the thread for a week or so but have not yet made a visual inspection of the inside of my unit, nor have I opened your images because I have been on my mobile phone only over the summer holidays. Nevertheless I am following the thread with fascination to see how you fare.

I have a good basic understanding and skill with electronic repairs but have never undertaken repairs on a tv, so I will be taking detailed notes on your LG 60PK550 journey, and probably asking a few questions if that's ok, before I attempts the repair . I’m completely open to any pointers you want to offer, or things that you may have done differently.
Kind Regards, Allan

[fireproof710]

Re: Lg 60PK550 Problem

Welcome Alan. Isn't it amazing just how much info one can find on the web? Hopefully we'll be able to get your TV going too!

[fireproof710]

Re: Lg 60PK550 Problem

Well, I think the proverbial goose has been cooked. After a very tedious bit of surgery, the IC was removed and replaced. It started out well. I found that daubing the little legs of the IC in flux greatly helped to make the joints without putting excess heat on it. It makes me winder what the heat tolerances are on those little guys because even with minimal contact with the iron, it really heats up quick. I cooled it between passes with a damp sponge to alleviate the heat. All went well until the last pesky contact. The pad burnt up so there was nothing I could solder the leg to. Strangely there is no trace leading away from the pad, so I don't know where to jump it to. There is another identical circuit with the same IC nearby and upon examining it, there is no trace leading away from it either. Maybee it connects to another pad under the IC itself? Maybee it was a ground? I'm letting the caps drain at the moment. I'll attempt to snap a pic or two through the magnifying glass and show you what I'm talking about.

[tom66]

Re: Lg 60PK550 Problem

That could be a no connect, not all pins are always connected.

[fireproof710]

Re: Lg 60PK550 Problem

As per the spec sheet that particular pin is called "FGND"

Attached are 2 pics. The first one is my freshly soldered circuit. The second is the untouched identical one for comparison. I'll go back and check all of the legs to make sure they have good contact. and aren't bridged anywhere although I was checking them all with a loupe as I went. Any particular advice for working with ICs? Is it possible I overheated it? I did have the forethought to order two of them. So I could theoretically pop this one off and have another go at it...

[tom66]

Re: Lg 60PK550 Problem

Maybe remove it and see if that trace wiggles under the IC, get a picture too. Generally I tack the corners first in an ugly manner, do all the pins nicely and then clean the edges. Use flux! It's nearly impossible to use too much flux, so don't be afraid.

[fireproof710]

Re: Lg 60PK550 Problem

Okay. That's exactly what I did: pin the corners first to hold it in place. I think I got the alignment pretty decent. I'll unsolder it now and post back with a pic of the underside in a few.

[tom66]

Re: Lg 60PK550 Problem

Do you use solder wick to remove the devices? If not, you should do.

[fireproof710]

Re: Lg 60PK550 Problem

It aint pretty but there it is. After the second removal, several of the pads and traces have pulled up but are still attached. I don't have any solder wick, but I do have one of these desoldering irons that I can use to clean it up:

http://www.mcmelectronics.com/product/21-8240

Any additional thoughts before round 2?

[tom66]

Re: Lg 60PK550 Problem

Sorry for not mentioning it previously, but you -really- MUST use solder wick. Solder suckers like that cause too much damage to a board. I don't know if that is repairable. If it is it will take a lot of work.

[fireproof710]

Re: Lg 60PK550 Problem

Perhaps tomorrow I might try tinning some extra fine insulated wire to the leads of the IC, follow the traces on the board and solder them to the joints.

[fireproof710]

Re: Lg 60PK550 Problem

No luck. It's EXTREMELY difficult to solder leads onto the legs of the IC. They're spaced too closely and I keep accidentally undoing the completed joints. Also it would appear that my soldering iron has a cheap tip. It oxidizes awfully fast and refuses to stay tinned. Lesson learned. I'll buy a better tip.

On the good news front, I found a part recycling co. that has my part for $85 after shipping. I ordered it and they said it should come on Tuesday at latest. Fingers crossed.

After all this, I'm going to need to have a LOTR or Star Wars marathon once the dang TV is back on the wall.

[Allan Woods]

Re: Lg 60PK550 Problem

I wonder how Fireproof went with the new board?

[fireproof710]

Re: Lg 60PK550 Problem

Update: Still no board. I ordered it and now I haven't been able to get ahold of the seller for over a week to see what the deal is. if I can't get through today, i'm going to call my credit card co. and have them hopefully reclaim my $85 so I can order one from ebay...