Lg 50pk750 help!!!!

[michael dranfield]

Re: Lg 50pk750 help!!!!

Thank You! Our TV went out 2 days ago same thing. I used Hamie's trick and got the test pattern. Could not find a replacement main board and could not see anything obvious on the old one sooo I put it in the oven (on wooden dowel rods) for 10 minutes at 390 degrees F. I let it cool before moving it and now my TV works! Thanks again!!

Well done !
This is more novel than my party trick with the black and decker paint stripper.

[2old2]

Re: Lg 50pk750 help!!!!

I would like to have seen the paint stripper episode but as a fly on the wall, I might have been a paint stripper fatality!

[LGinMD]

Re: Lg 50pk750 help!!!!

2Old2,


Im going to have to try this out!

I have 2 main boards so hopefully ONE of them works!

Ill update after trying this

[2old2]

Re: Lg 50pk750 help!!!!

It will only help if a cracked or cold soldered joint is causing the failure. Good Luck LGinMD!

[LGinMD]

Re: Lg 50pk750 help!!!!

Update,

Im sad to say that the first board I put in the oven didnt make it out alive.. While using gloves to pull it out I managed to literally wipe off the tiny resistors soldered to the bottom of the board...

On the second go around I learned from my mistake and didnt remove anything, however, it made no difference

So, Im still without a TV and am thinking I should just part it out and buy a new one...

[2old2]

Re: Lg 50pk750 help!!!!

Sorry to hear that LGinMD. Yeah you have to let it cool in place.

[capwizard]

Re: Lg 50pk750 help!!!!

I thank you all.

After a good patterns* tested , A Main Board** needed, but it's out of stock. So I use a paint stripper*** heat the main board and it worked. Saved $129.24+shipping.

*LG 50PK750 TRAINING MANUAL Service Manual free download.


** LG EBR60870105 (EAX61557903(0)) Main Board http://www.shopjimmy.com/lg-ebr60870...50pk750-ua.htm

***a paint stripper: harbor freight 1500 Watt Dual Temperature Heat Gun.

[JeffJ]

Re: Lg 50pk750 help!!!!

I know this thread is old, But add me to the list for Main board repair. Someone left this at our ewaste Depo, said some kid on Facebook charged them to fix it and it never worked after they got it home.

Used my rework statation, preheated the board to 125C, put on clean free liquid flux and flowed it into the BGA, then gave it 200C on the chip for 60 seconds then ramped up to 290C, for 30 seconds, then up to 385C for 30 seconds then backed if off slowly down to 125C and let it cool naturally after that.

I modified the heatsync to take a 12v fan that uses 130mA and once i find a proper source for the 12v for it i will post pics.

[JeffJ]

Re: Lg 50pk750 help!!!!

Ended up running the fan from 5V, Keeps the CPU heatsync at a consistent 25C before it was 40-50C

Should last a nice long time now.

[frustrated plasma]

Re: Lg 50pk750 help!!!!

Ended up running the fan from 5V, Keeps the CPU heatsync at a consistent 25C before it was 40-50C

Should last a nice long time now.

Do you mind telling us how you did this?

[tedj13]

Re: Lg 50pk750 help!!!!

Just to clarify for test Patterns.

On the control board disconnect the LVDS cable. This cable is labelled P31.
The 2 holes you need to connect together with a paper clip or bit off wire are close to P31 beside the 2 resistors marked R51 and R52.

If you get test patterns you have a faulty mainboard.
Unfortunately the board is usually quite expensive as it in high demand.

I know this is an old string, but I'm trying to troubleshoot my lg 50pk750. I have tried the control board test and when I disconnect the LVDS cable and then jum the r51 and r52, then plug the TV in and power it on, I do not get the test pattern. Does this mean the control board is bad, and if so how do I troubleshoot it?

[tvtimmy]

Re: Lg 50pk750 help!!!!

What are your symptoms? Relay clicking? Something else?

[tedj13]

Re: Lg 50pk750 help!!!!

My symptoms are when I turn on the TV the front red light turns Blue and clicks. after about 5 seconds the light turns red. after about 10 more seconds when I hit the on/off button the light goes blue and I hear a click, and then the light goes red and then off. I don't believe it is the mainboard because I have checked the voltage from it and it is all ok. I replace the voltage regulator on the main board and I get the same results. Thanks for any and all help.

[tvtimmy]

Re: Lg 50pk750 help!!!!

Check the 3 fuseable resistors on the power supply. Measure them in ohms and in continuity mode. I have a feeling one is bad. Should read 10 ohms and dead short in continuity.

[tedj13]

Re: Lg 50pk750 help!!!!

So I checked all three, and 2 of them read 10.1 and the third reads 10.3, so I assume that is the bad one. Any suggestions on where I can get a replacement, I can't find one on shopjimmy or amazon. The part says 5w10r0j, and I have one that says 5w 22ohmj. I assume the 22ohm is to big to use as a replacement. I also have a 5wr0j5, but I assume it is too small.

[R_J]

Re: Lg 50pk750 help!!!!

The resistors are ok, If they were bad they would measure open. They are well within tolerence.
Monitor the Vs voltage with your meter when you first turn on the tv and see if it comes up the drops down.
If it does not come up, disconnect the plug going to the Ysus board and try again.

[tvtimmy]

Re: Lg 50pk750 help!!!!

Yes, they are good.

[tedj13]

Re: Lg 50pk750 help!!!!

The resistors are ok, If they were bad they would measure open. They are well within tolerence.
Monitor the Vs voltage with your meter when you first turn on the tv and see if it comes up the drops down.
If it does not come up, disconnect the plug going to the Ysus board and try again.

I'm a novice at this, what is the Vs, and which one is the Ysus board, thanks for all your help!