LG 50PK350 Plasma

[rigeback]

Re: LG 50PK350 Plasma

That's it the PSU don't boot anymore it just clicks away!
RL_ON is missing and seems to suggest IC701 has a problem. STB_BY is still present.
These test were performed;

A) Ground the Auto Gnd Line (Pin 18) will allow the supply to be powered up one section at a time.
(B) Add a 100Ω ¼ watt resistor from 5V Standby to RL_ON and the 17V
and 5V Run Lines on P813 will become active. Also AC-Det (4.06V)
and Error_Det (4.1V) become active.
(C) Add a 100Ω ¼ watt resistor from any 5V line to M_ON to make the
(Monitor) M5V, VS and VA lines operational.
P811, P812 (VS pins 1 and 2) and (VA pins 5 and 6).

M_ON is present on the board but RL_ON can't activate it.
Moral of the story its a big paper weight if I don't order a new PSU.

[rigeback]

Re: LG 50PK350 Plasma

This sounds promising and probably the way I'll go before forking out 100 bucks for ran old TV, https://www.badcaps.net/forum/showth...ighlight=IC701

[rigeback]

Re: LG 50PK350 Plasma

After re-reading https://www.badcaps.net/forum/showth...50PK350&page=2 and taking some readings I think Tom is right about the optocouplers as the AC_DET is dead unless pulled up from STD_BY 5V and even so it will not stop the relay closing (Clicking).
The Yellow circled optocoulpler has 105 - 300 V on one side and nothing on the other? The rest all have readings.
I would like to de-solder but I am not sure what to replace it with, in saying that I have a few from other PSU's but not sure they will work, I have not been able to locate a schematic for this board.
Any positive thoughts would be welcome.

[tw2005]

Re: LG 50PK350 Plasma

Mate, I've really got nothing for you I'm afraid.

[rigeback]

Re: LG 50PK350 Plasma

Yeh its a bummer knowing what to get here, new IC701 or new board,, or pull 5V on the optocoulpler instead of after the IC701, could be fun and games though!

[rigeback]

Re: LG 50PK350 Plasma

Another thing noticed is mossfet D352 is reading very high DC voltage on the ground side pins that connect to the alloy bar on the secondary side, this can't be normal and seems to me its shutting everything else down??? Although on the + pin there is 17-20V fluctuating.
Might go ahead and remove to see what changes.

[matyka]

Re: LG 50PK350 Plasma

hi, I have the same lg 50pk350 with the same fault.
I have replaced the IC701,IC301,D304,R929,R928,R927 all this with new parts
I have changed all the smd R108,R109,R110,R111,R103,R104,R105,R106,R107 somebody suggested and I have the same fault nothing changed .
I have stdby all the time .
I have 5.2v on AC_DET and it drops to 0v when clicking.
Could anyone help with this problem please.
PCB:EAX61392501

[matyka]

Re: LG 50PK350 Plasma

Could someone tell me what to do with this optocouplers as Tom said before .
Do you have to short them ? I have pull them out from circuit and they measure fine.

[niblettr]

Re: LG 50PK350 Plasma

As a guess, try attaching a 1k resistor from the 5.3v supply pin to AC_DET and see if that holds up.

[vinceroger69]

Re: LG 50PK350 Plasma

wrong thread ignore please

[matyka]

Re: LG 50PK350 Plasma

Hello,after I checked the board for soldering I notice EYS10 had dry joint.
I resolder on all transformers all pins and the tv is working with no intermittent clicking .

[niblettr]

Re: LG 50PK350 Plasma

Nice one.

[4evermetalhead]

Re: LG 50PK350 Plasma

Hi all,

I have the same issues as most of you people on my 50PK350.
My problem though is that the damn resistors (2 resistor configuration, i dont recall the boards model now), keep burning.
I had five of those laying around at work, i knew that those were from China, still that does not explain much as even chinese made does not necessarily mean bad.

Anyway, i originally found that one my resistors was blown. So i replaced it and that worked for about a week or two max.
Then the other resistor was blown that i did not replace. So i thought that makes sense, cause i should replace both in the first place.

So long story short it could remain working for a day and next die on me again or it could take up to a week to fry the resistors. Well now i am out of resistors so i ordered some more from UK (also made in UK). Hoping that this will fix the problem once and for all by using "good known quality ones".

Anyone though has any idea what is causing this? Keep in mind that this could last me a day or up to a week or so.

Thanks.

[Hamie]

Re: LG 50PK350 Plasma

Hi all,

I have the same issues as most of you people on my 50PK350.
My problem though is that the damn resistors (2 resistor configuration, i dont recall the boards model now), keep burning.
I had five of those laying around at work, i knew that those were from China, still that does not explain much as even chinese made does not necessarily mean bad.

Anyway, i originally found that one my resistors was blown. So i replaced it and that worked for about a week or two max.
Then the other resistor was blown that i did not replace. So i thought that makes sense, cause i should replace both in the first place.

So long story short it could remain working for a day and next die on me again or it could take up to a week to fry the resistors. Well now i am out of resistors so i ordered some more from UK (also made in UK). Hoping that this will fix the problem once and for all by using "good known quality ones".

Anyone though has any idea what is causing this? Keep in mind that this could last me a day or up to a week or so.

Thanks.

Yes you need to change out this capacitor here:
Check it with an esr meter, It will be through the roof.

I believe the purpose of the 2 resistors is to drain the caps on y and zsus.
When you turn off the tv this capacitor is used in that circuit.

Usually when I repair this power supply I change out the 2 resistors, the mosfet below them and that capacitor.

Also if you just change the capacitor and the resistors without changing the FET it tends to blow almost instantly.

[Hamie]

Re: LG 50PK350 Plasma

Pic

[tw2005]

Re: LG 50PK350 Plasma

Hello,after I checked the board for soldering I notice EYS10 had dry joint.
I resolder on all transformers all pins and the tv is working with no intermittent clicking .

good tip, lost count of how many bad or broken joints my board had. Was the whole issue.

[kthxbia]

Re: LG 50PK350 Plasma

Hello,

I have a 50" LG 50PJ550 TV that was displaying the following symptoms. It would run for 1-2 hours and after this time period it would turn itself off and then take approximately 5 minutes before you could turn it back on again. Sometimes it would shut off after 30 minutes of use and sometimes 2 hours. I took the power circuit board out and checked the 3 resistors on the top right of the board which all had approximately 10 ohms resistence (good). I checked the 3 fuses which were good and the diode that most people are recommending to check which was good.

So how did i fix this board?

A person on this thread commented that they found some bad solders in a particular area of the board. To me the solders looked fine but you could tell some of them were displaying symptoms of "dry solder". I found 3-4 that were displaying these traits and I re-soldered them. This completely fixed the problem and the tv has not shut off since.

I wanted to post this because many people say you need to buy kits and replace parts when it is very simple to fix this shutting off problem. PLease refer back to the wonderful person that previously commented on the area that the solders were failing because this was the area mine was failing in as well. Thankyou for commenting about this problem and I hope to help in posting this response as well.

[pat0te]

Re: LG 50PK350 Plasma




Yes you need to change out this capacitor here:
Check it with an esr meter, It will be through the roof.

I believe the purpose of the 2 resistors is to drain the caps on y and zsus.
When you turn off the tv this capacitor is used in that circuit.

Usually when I repair this power supply I change out the 2 resistors, the mosfet below them and that capacitor.

Also if you just change the capacitor and the resistors without changing the FET it tends to blow almost instantly.

Sorry for write on this old thread but recently I got an LG 50PK350 Plasma that I wanted to repair for few euros (Spain) and I can confirm about small capacitor. I have only a multitester to check capacitance, so I replaced this capacitor to stop burning ceramic resistance. Thanks Hamie!

[pat0te]

Sorry for write on this old thread but recently I got an LG 50PK350 Plasma that I wanted to repair for few euros (Spain) and I can confirm about small capacitor. I have only a multitester to check capacitance, so I replaced this capacitor to stop burning ceramic resistance. Thanks Hamie!

Well, unfortunately same failure come back after months of normal use. Tv try to start, flash lamps for less than a second and then, clicking noise for a couple of loops and red standby led again.
I will try changing every capacitor on the supply board.