Lg 50pk750

[tvtimmy]

Re: Lg 50pk750

Dont bake it!!! Remove the 4 spring loaded heatsink keepers. Peel off the rubber heat pad and save it. Use a heat gun(paint stripper) on low and go over the bga chip for about 45 seconds with the smallest tip you have. Apply some heatsink grease or compound to the chip and the rubber pad and put the keeper studs back in. Let us know if it worked(it should) and for how long. You have nothing to loose.

[frustrated plasma]

Re: Lg 50pk750

Ok, I will try this, but it will take a few days before I can get back with results. I'm currently living in Germany, so I don't have any of my old 110V tools. I'll need to source a heat gun and some thermal compound.

So, definitely don't bake it? I could easily do that in the next day or so, but if the heat gun is the better way to go, I can explore options of where to get one.

Thanks again!

[frustrated plasma]

Re: Lg 50pk750

Remove the 4 spring loaded heatsink keepers.

Where do I get the tool to remove the pins?

[tvtimmy]

Re: Lg 50pk750

I use a tweezers to pinch it together and my fingernail to pull it up. There is a spring under the head of it. You might use a needle nose to pinch the bottom side of it.

[rccrasher65]

Re: Lg 50pk750

+1 Other option, is to find someone in your area that will reball your BGA chip on main board. most computer repair guys can do this. A good chance board will work, thats the more permanent fix.

[tvtimmy]

Re: Lg 50pk750

+1 the problem is the tree hugger friendlly lead-free solder is too "stiff". No chance for the movement of things when they heat up and cool down. The solder balls under it loose their connections.

[frustrated plasma]

Re: Lg 50pk750

Ok, I got the heat gun, and I'm headed to a computer store for the thermal paste. I will ask if they can do a re-ball there. If not, what temp should I use the heat gun at? On the low-end is 130F, obviously way too cool, but infinitely adjustable to approx 900F. Where on the scale of "hair dryer" and "scorched earth" should I use? Give me C or F and I'll convert.

Thanks all!

[frustrated plasma]

Re: Lg 50pk750

Ok, it worked, tv appears to be fully functional! A couple things:
- Computer supply/repair place could not do a reball, so I did the heat gun method.
- I saw a video saying reball/reflow is BS, it's a chip quality issue. Stated that lead-free solder has a higher melting point, so the reflow/reball at the lower temp isn't really the fix, it's that you're heating the chip.
- Rather than high heat for a short time, I did low heat (250-300 F) for 5 mins, as measured by digital thermometer.
- Thermal pad + thermal paste is not recommended by another site. Says heat conductivity is actually worse. It says if you have a pad, replace the pad. Thoughts?

Anyway, thanks for the advice! Hoping to get another year+ out of this tv before replacement!

[tvtimmy]

Re: Lg 50pk750

Glad you fixed it!

[dick_barton]

Re: Lg 50pk750

You can find new thermal pads on Ebay. It's needed to remove the heat from the IC. The constant heating/cooling is what tends to break the solder joints under the chip. The fix however may only be temporary but will give you sometime to perhaps find someone local who does BGA reflows. Often people who repair Playstations.

[frustrated plasma]

Re: Lg 50pk750

I'm going to go to the same computer supply place and see if I can get a new pad. I'm also looking into adding a 5v fan as pictured in another 50pk750 thread.

Of course, a local store has a Samsung UN55ks 8000 on sale for $800. It would be a nice replacement if this repair craps out quickly.

Thanks again!

[KYBOSH]

Re: Lg 50pk750

Most of the boards in the LG PK range are transferable, it shares the same y&z and cntl board.
As Andrew says this board should work fine.

I hate to bring a thread back from the dead but there's some pretty good information in here and I'm experiencing the exact same issues with the TV I just picked up.

Rather than start a whole new thread I'd like to ask if anyone knows Which mainboards are interchangeable within the PK-series.

[KYBOSH]

Re: Lg 50pk750

To give a little more context i did the test pattern test mentioned above and found that the mainboard is the most likely culprit.

I looked over the board, testing, probing, looking for shorts amd found nothing. Everythjng looked good. I thought it maybe an EMMC issue but read about the BGA being the moat likely problem. I put some heat to the processor for a little while and tried it in thr set but no joy. I noticed the PCB was a little bowed around the BGA but i dont know if that was a result of me heating the chip or if it was always there (a result of the thernal pad and heatsink pressi against the chip for the last 13 years).

Anyway i wanted to see what the market for replacment boards while i continued troubleshooting. I came across this thread and saw that a nunber of board will work.

I also nocticed tbat the board that is in this TV, EAX61557904 (1)
, is not native to the 750 series but rather the 950. This is based on my googling.

This is why inwant to verify the compatibility of boards across the PK series. This board may actually be good but not compatible with thjs TV as i dont know what, if anything the previous owner has done with it.

Thanks in advance!

[lotas]

Re: Lg 50pk750

There is no eMMC here, NAND Flash here and the board matches the 750 model as well.

[KYBOSH]

Re: Lg 50pk750

Thank you for your response @Lotas. Always a pleasure getting correction from you.
Yes you are right... My mistake I meant to say a BIOS issue rather than EMMC issue. I think I had another TV on my mind when I wrote that.

Also I checked shopjimmy.com, tvpartstoday.com as well as a few others and they all had EAX61557904 (1) as belonging to a PK950 with no mention of any other compatibility.
ShopJimmy is usually very good about listing other TVs their parts are compatible with so I often trust them without question but now I will have to do more in-depth research on compatibility.

The TVPartsGuy webpage you reference is the only place that lists this board as compatible with a PK750. I dont know if that is a mistake but it is certainly an outlier which I have yet to verify.
Not saying it isn't compatible... Im I just want to be absolutely sure before I proceed to the next step. Even ordering another board would depend on this step as you should try to order the same board (part number) that came with the TV whenever possible.

But that's kind of why Im asking here.
To see what the hive mind might know or at least where to look.
Im not aware of an official LG parts supplier webpage that has in-depth information on LG TVs, parts and accessories like samsungpartsusa.com.

Edit To Add:
I just found the service manual incase anyone needs it in the future.
I will go through it and see what it says about different MBs and report back.