Lg 60PK550 Problem

[fireproof710]

Re: Lg 60PK550 Problem

Update. Got a replacement Zsus board from shop jimmy. Installed it and the resistor still measures 15v instead of the 105 it should. Interesting find though, I kept the leads on the resistor and had someone toggle the power. The reading initially jumps up to 93V and then slowly drops down to 15.

SO. I'm going to test the power supply again. I did notice a faint ticking that sounds like it is coming from one of the heat sinks on the power board. What are those little 3 legged square components that are screwed to the heat sinks?

I'll report back after I re-check the power supply.

[fireproof710]

Re: Lg 60PK550 Problem

Attached is a pic I made that documents the voltages I get coming off of the power board going to the main board. I used a needle as my positive probe and probed the pins in the jack itself so I could leave it connected. Does any of this information tell you anything? the 2/3v on Error_Det indicates that it was flickering between 3 and 4 v. I also took similar notes on all the other jacks coming off of the power board going to the Ysus Zsus and logic boards if that information would be useful.

As an aside, while I was probing around on the Power board/Main board jack, The the relay clicked off and once I powered it back on the display worked. So I toggled it on and off a few times. After about 3 cycles, it went back to its dormant state. I may have accidentally bridged a couple of pins as I was probing, but not knowing what I did (if anything) I couldnt replicate the results. While the display was on, I measured the Zsus resistor on the board I had just swapped out and got a steady reading of 110v while it was on.

Does any of this make any sense? ShopJimmy is sold out of the power board I need, and it's $160 anyway. Being $50 into this with a likely unnecessary Zsus board. I'd love to be able to fix this cheaply.

Also...

MERRY CHRISTMAS EVERYONE!!!!

[fireproof710]

Re: Lg 60PK550 Problem

So, more interesting findings. If I leave the tv powered on, after 15 or so minutes pass, the auto-off feature activates. If I turn it back on right after this happens, the tv will turn on. After turning it on and off 3 times, it refuses to turn on again. THese results are reproducible and not random, so I'm starting to think that there's some weird goings on in the power board. As I mentioned before, I'm hearing a faint, rapid ticking sound coming from the board when it is malfunctioning, but when it is working properly, I don't hear it. Could this have anything to do with it? What components are capable making ticking noises if not working properly?

At this point I'm ready to start replacing components on the main board to try to fix this if need be. I listened for where the ticking was coming from and I have uploaded a picture of the power board with a red circle around the area I believe it to be coming from. I listened as close as I could, without risking touching the board with my ear. Could you imagine that? several hundred volts straight to the ear? That would not be a good time. I digress.

Can anyone recommend any further things to test? There's got to be some way to fix this thing!!!!

[freakaftr8]

Re: Lg 60PK550 Problem

Bet its a voltage regulator. Try heating the power board and power up

[fireproof710]

Re: Lg 60PK550 Problem

I took a heat gun and gently ran it over the board for a minute or two. Bingo. It powers on under the influence of heat.

I'm thinking a good idea would be to turn it on cold and test each regulator to identify the faulty one. If I understand correctly, to test a regulator, I need to ascertain the output voltage it's regulated for and check the output pin? I know that a good guideline when replacing capacitors is to just go ahead and replace others in the same product line just in case. Is it a similar deal with regulators? Or should I just focus on finding the faulty one and replacing it?

[newtothis]

Re: Lg 60PK550 Problem

yes

[tom66]

Re: Lg 60PK550 Problem

For a power board I'd look for cold solder joints and bad capacitors.

[fireproof710]

Re: Lg 60PK550 Problem

Awesome. Thanks for all the advice. I think I'll pick up a decent soldering iron tomorrow (i've got a junky one) and reflow any dubious looking joints. Hopefully it's just a bad joint. If not, I'll check the voltage regulators and take a closer inspection of the capacitors.

[fireproof710]

Re: Lg 60PK550 Problem

Update. I took the power board off and inspected the joints paying special mind to the voltage regulators. It was kind of difficult for me to discern which joints are good or bad, so I added a bit of flux and re-flowed a few of them. I also added some solder to a couple that looked a little skimped out. I plugged it all back in and nada. @Tom66 I also checked the capacitors closely and didn't see ANY bulging at all, nor did I see any of that brown goo that sometimes leaks from bad caps.

I proceeded to check the voltage regulators starting with the ones screwed to the heat sink where the ticking was coming from. I apparently have no idea how to check a voltage regulator. I was getting readings all over the place on both the input and output pins. One problem might be that my multimeter isn't auto ranging. I looked up the spec sheets on the 2 types of VR involved and both say that the input is +/- 30v but that didn't seem right to me when I checked it. I also may not be correctly interpreting the spec sheets.

Anyway...

When I checked the topmost VR, when I probed what I believe to be the input pin, the ticking noise sped up. Thinking that was fishy I tried heating up that VR by itself and after a minute or so of heating, I pressed the button and it turned on. I think I may have found the faulty component. @freakaftr8 does that sound probable?

So now I have 3 questions:

1) Is it legitimately conceivable that a voltage regulator could emit a ticking noise?
2) If I order a replacement should I also go ahead and replace the neighbouring VR that is the same type, just for prudence's sake?
3) What is the turquoise colored component to the right of the VR and heat sink? I fear I may have damaged it during my over zealous heating of the voltage regulator. There is a little tear in the casing that I didn't notice before that looks like I could have melted it. It was pretty hot to the touch.

[freakaftr8]

Re: Lg 60PK550 Problem

That cyan color component is a mylar non polarizrd capacitor. Can you take a close up pic of the voltage regulator? These LG power supplies are hard on these regulators. I have one here now with a shorted regulator. Different model same scenario.

[fireproof710]

Re: Lg 60PK550 Problem

Attached are 2 pics. One is of the regulator. One is of the adjacent capacitor I may have cooked.

The regulator appears to be a Toshiba K15A60U. Mouser doesn't carry them but DigiKey does:

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

Should I replace that capacitor just in case?

[vinceroger69]

Re: Lg 60PK550 Problem

that capacitor looks to have a crack in the casing yes i would replace it and while you are it i would change the small 2 in front of the voltage regulator just in case as your doing a order anyway imo.

[freakaftr8]

Re: Lg 60PK550 Problem

Agreed, replace all capcitors in that section to start, That mosfet is not a voltage regulator like I thought, instead it delivers the VS voltake to the sustain boards. I would more focus on the capacitors in the area to start.

[fireproof710]

Re: Lg 60PK550 Problem

Alright. I'll go ahead and replace all of the smallish capacitors on the board as well as the mosfets that are on that particular heat sink. Could anyone give me some guidance on what capacitors to buy? I need:

4x 50v 10uf
3x 50v 33uf
1x 63v 47uf
1x 25v 220uf
1x 10v 470uf
2x 16v 100uf
2x 50v 100uf

I know nothing as to what brand, type, series, tolerance etc. that would make for good replacements. also, I'm having trouble identifying that mylar capacitor. Attached is a pic of the only identifying marks on it.

[sam_sam_sam]

Re: Lg 60PK550 Problem

If I was doing this repair I would use the following part # from Digi-Key

4x 50v 10uf...> 565-1598-ND or 565-1702-ND
3x 50v 33uf...> 493-1895-ND
1x 63v 47uf...> 565-1855-ND or 493-1934-ND
1x 25v 220uf...> 565-1546-ND or 565-1674-ND
1x 10v 470uf...> 565-1501-ND or 565-1643-ND or 565-1902-ND

For these I would use the same part #
2x 16v 100uf...>565-1545-ND
2x 50v 100uf...>565-1545-ND

"Attached is a pic of the only identifying marks on it" I wish I could help you with this one I have no Idea ethier

I use these most often KY KZE LXZ and when I can not them in these series then I will use PW
or FM FC FR

I hope this helps

I fix so many TV and power supply lately that I have to order 1uf, 2uf, 2.2uf, 4.7, 10uf, 47uf @ 100 at a time

One LCD TV a week ago had a lot of 10uf and 1uf in it

[fireproof710]

Re: Lg 60PK550 Problem

Thanks for the advice on which caps to order. Hopefully if I can get this TV working, I'll continue to fix tvs as a hobby and may end up having to buy them in larger quantities like you.

I REALLY hope someone can help identify that mylar capacitor. Somebody has to know what those marks mean!!!

[sam_sam_sam]

Re: Lg 60PK550 Problem

One note about the one that I look up for you check the size to make sure they fit
meaning these


1x 25v 220uf...> 565-1546-ND or 565-1674-ND
1x 10v 470uf...> 565-1501-ND or 565-1643-ND or 565-1902-ND

If you have room for there size if there no other caps or other item that are in the way then these should work for you if there are other thing in the way then you may have find smaller size in diameter or some time the caps can be to tall

Here is a step by step how we find the caps that we need

Frist go to

www.digikey.com/

Then go to product search

www.digikey.com/product-search/en

Then go to capacitors aluminum capacitors

https://www.digikey.com/product-sear...acitors/131081

Then pick the voltage an uf value and ...> ( size if need )

[freakaftr8]

Re: Lg 60PK550 Problem

I'm stumped on that capacitor. I'm researching though.

[freakaftr8]

Re: Lg 60PK550 Problem

It may be a .022 if 1800v though don't quote me yet.

[fireproof710]

Re: Lg 60PK550 Problem

you guys are fantastic!

@sam_sam_sam: There are no other components crowding the caps I need to replace, so as long as the ones you suggested aren't inordinately large, they should be fine.

@freakafter8: Thanks so much for hunting that down for me, I anxiously await your conclusions.