LG 50PK350 Plasma

**freakaftr8** · 03-03-2014, 10:16 AM

Re: LG 50PK350 Plasma

I would certainly change the voltage regulator as well. It will short again. Right now its intermittent and will test good but it will go soon for good. They short temporary under heat taking.the diode out.

Ask me how I know. Lol

**PowerAmpFreak** · 03-03-2014, 12:30 PM

Re: LG 50PK350 Plasma

D304 is in parallell with R305 which is low resistance. So you have to take D304 out of the circuit to measure it properly.

**rigeback** · 03-03-2014, 01:34 PM

Re: LG 50PK350 Plasma

Thanks for the good advice, I'm glad I started the thread before going my own way. I'll remove D304 and wait on the repair kit before I put the board under load again.
Thanks again.

**rigeback** · 03-10-2014, 12:39 PM

Re: LG 50PK350 Plasma

D304 is in parallell with R305 which is low resistance. So you have to take D304 out of the circuit to measure it properly

.
Parts arrived today so removed D304 and measured R304, very low resistance 1.5 Ohms.
D304 on the other hand has a much lower reading than the new diode which seems suspect. The 3 ceramic resistors measure up the same as the old ones so will keep the old ones on the self.
I imagine that voltage regulator IC301 is on its way out so will replace it first since the solder area is tight.

**rigeback** · 03-12-2014, 04:53 PM

Re: LG 50PK350 Plasma

Installed the kit and its same as before, still clicking away and eventually coming on, watched TV this evening and the pictures okay once it comes on.
I'm going remove the SMPS again tomorrow and do a static test and check the optcouplers that were mentioned in Toms thread, the symptoms are identical to mine in many ways https://www.badcaps.net/forum/showth...50PK350&page=2

**rigeback** · 03-20-2014, 08:09 AM

Re: LG 50PK350 Plasma

This TV is starting the same frustrating clicking as before and its time to make a quick fix, the 5V stanby is dropping out to 3 .5V during the clicking and I would prefer to install a resistor

An alternative: Can you acquire a 1k ohm resistor? It might be possible to pull up the AC detect line. This depends on the main board having control over the power supply (which it might have, as it has an RL_ON line, and on the 42PC1D I worked on, the main board *did* control most power supply functions.) It also depends on 1k being sufficient - you may not be able to override the power supplies' signal so it *may* mean you need to cut a wire and splice in the resistor. I'm in favour of the AC detect optocouplers though

.

I would appreciate any guides regarding: The best point to install the resistor? AC_DET and 5V ? The PSU has RL_ON line

**tom66** · 03-20-2014, 09:14 AM

Re: LG 50PK350 Plasma

I don't think bypassing AC detect on this model will fix the problem.

**rigeback** · 03-20-2014, 09:27 AM

Re: LG 50PK350 Plasma

The problem is I'm not sure if I will be able to source the opto-couplers locally for this PSU and the timing, I already waited 3 weeks on the other parts that were a waste of time.
I will order the parts later but for the kids I just wanted a quick fix, I'll give the resistor a try.

**rigeback** · 03-20-2014, 10:48 AM

Re: LG 50PK350 Plasma

Originally posted by rigeback

The problem is I'm not sure if I will be able to source the opto-couplers locally for this PSU and the timing, I already waited 3 weeks on the other parts that were a waste of time.
I will order the parts later but for the kids I just wanted a quick fix, I'll give the resistor a try.

Got the board off and trying to see a part number for the opto-couplers but none of them have any clear part numbers just PC109 and PC103 printed on the board, is there a way to identify what part number to order, thanks.

**rigeback** · 03-21-2014, 05:01 AM

Re: LG 50PK350 Plasma

I don't think bypassing AC detect on this model will fix the problem

Yes you're right unless 220 Ohms is too heavy, might try with 1 Ohm resistor, what else could be causing the Standby problem?

**tom66** · 03-21-2014, 05:52 AM

Re: LG 50PK350 Plasma

Did you replace the regulator IC as Freak suggested above?
Do not use a 1 ohm resistor.

**tw2005** · 03-21-2014, 06:09 AM

Re: LG 50PK350 Plasma

Originally posted by rigeback

.............. the 5V stanby is dropping out to 3 .5V during the clicking ................

I would appreciate any guides regarding: The best point to install the resistor? AC_DET and 5V ? The PSU has RL_ON line

"Any time AC is applied to the SMPS, STBY 5V will be 3.46V and will
be 5.14V when the set turns on.
AC DET WILL NOT be present until set comes on.
If AC Det is missing, the TV will come on and shut off in 10 Seconds."

**rigeback** · 03-21-2014, 07:13 AM

Re: LG 50PK350 Plasma

Yes the IC and 3 2.2 Ohm ceramic resistors were replaced along with D304, the fuse was not replaced as the TV still works occasionally.
Yes the STBY 5V did indicate the 3.4V as it was trying to startup and there is no ACDET during startup, RL_ON line measures 2V.

D304 still seems suspect as it reads shorted on the board but good with one leg lifted as with R304 test to ground?

**tw2005** · 03-21-2014, 07:31 AM

Re: LG 50PK350 Plasma

Originally posted by rigeback

.........so I ordered a repair kit *LG Repair KIT [Power Board] EAY60968801* ...........I decided to remove the PSU and check the components that are on the way, I also removed the 3 ceramic 10 Ω resistors tested okay off the board 2.2 ohms set at 200 Ω.
.........

just trying to clarify some things that's confusing me.

You removed 3 x ceramic 10ohm rsistors and they tested ok at 2.2ohms?

So the 22ohm ceramics x 2 (R927 AND R929) were good too?

Is this picture your board and the components supplied in the kit which were replaced?

Attached Files

**tw2005** · 03-21-2014, 07:34 AM

Re: LG 50PK350 Plasma

Originally posted by rigeback

Yes the IC and 3 2.2 Ohm ceramic resistors were replaced along with D304, the fuse was not replaced as the TV still works occasionally.
Yes the STBY 5V did indicate the 3.4V as it was trying to startup and there is no ACDET during startup, RL_ON line measures 2V.

D304 still seems suspect as it reads shorted on the board but good with one leg lifted as with R304 test to ground?

if it tests good with a leg in the air, then it's good. A diode in parallel with a 1.5ohm resistor will always look shorted in cct if you meter it.

**tw2005** · 03-21-2014, 07:45 AM

Re: LG 50PK350 Plasma

Originally posted by rigeback

...... STBY 5V did indicate the 3.4V as it was trying to startup and there is no ACDET during startup, RL_ON line measures 2V.

sounds normal, they quote (2.43V) for RL_ON

**rigeback** · 03-21-2014, 07:58 AM

Re: LG 50PK350 Plasma

just trying to clarify some things that's confusing me.

You removed 3 x ceramic 10ohm rsistors and they tested ok at 2.2ohms?

So the 22ohm ceramics x 2 (R927 AND R929) were good too?

Is this picture your board and the components supplied in the kit which were replaced?

Yes this is the board its almost the same except mine has 3 X 2.2 Ohms ceramic resistors R927 - R928 - R929.

**rigeback** · 03-21-2014, 08:01 AM

Re: LG 50PK350 Plasma

I would like to run it on the bench here without a load but I've read it could do more damage without a load, on another model 50PJ350 which I have the training manual they indicate setting up a static load with 100W globes

**tw2005** · 03-21-2014, 08:12 AM

Re: LG 50PK350 Plasma

must be a variant then, so they're marked 2r2.

I'd be tempted to try running it without the mainboard and Placing two 100 Watt light bulbs in series from Vs to Ground and see if it remains stable.

have you got any training guide like 50PJ350? Virtually same design to get the procedure?

LG 50PK350 Plasma

LG 50PK350 Plasma

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