LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

[Michale32086]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

So what does that tell you?

OK, looking at the diagram is a lot tougher than reading the process on page #50..

But one thing confuses me. Well a LOT confuses me, but one thing stands out..

The page talks about plugging in and powering on.. With this particular TV, they appear to be one and the same..

So, I am going to assume that they are the same, as when I plug the TV in, it appears to go into power up mode..

OK, as I read it, then the TV is powered up, the Microprocessor IC701 is energized and sends a signal (5v) to the RL-ON.. I think I am getting that.

The second signal by IC701 is sent to ML-ON which I am NOT getting..

So, based on that, I would have to conclude that IC701 is wanky..

Howz dat??

[CapLeaker]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

I meant to write

"Pop quiz, hotshot." What does that tell you?

From the movie Speed starring Keanu Reeves.

I'll be back!

Terminator - Arnold Schwarznegger

[Michale32086]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

I meant to write

"Pop quiz, hotshot." What does that tell you?

From the movie Speed starring Keanu Reeves.

There ain't hardly ANYTHING in this world that can't be addressed with a movie quote!!!

As to what it tells me??

It tells me that I need to study those manuals...

[retiredcaps]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

I meant to write

"Pop quiz, hotshot." What does that tell you?

From the movie Speed starring Keanu Reeves.

[retiredcaps]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

Just FYI, there is 0v on M_ON when the unit is plugged in...

So what does that tell you?

[Michale32086]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

Not a problem whatsoever, RetiredCaps.. I know that my ignorance is only surpassed by my eagerness to learn.

I'll review all the links and am downloading the manuals right now..

Just FYI, there is 0v on M_ON when the unit is plugged in...

Thanx again for all the great info and links..

[retiredcaps]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

There are so many things here I don't know where to begin. I know you are a beginner and enthusatic to learn, but you must have a bit of thick skin reading my comments/suggestions.

None of this is meant as malicious, only to help you. A bit of tough love.

1) When you don't know if resistance should be measured with power on or off and that your meter has a diode test function, it is back to multimeter basics 101.

You need to learn how to use and interpret readings on a multimeter before continuing. The manual is short and simple and that should be mandatory reading (yes, I read it).



More importantly, you need to know how to interpret the readings. Chapter 7 of this book



tells you the building block components. It tells you what they are, how they work, why they fail and how to test them. And yes I have read the book from my local library and it is excellent.

2) I know you have a new scope, but you should put that aside for now until you get more experience.

You should watch some youtube training videos and this one "EEVblog #279 - How NOT To Blow Up Your Oscilloscope!"

https://www.youtube.com/watch?v=xaELqAo4kkQ

3) If you are going to do more of this repair, you need a better camera with a macro mode and better lighting. You can get an used Canon digital camera with macro mode from craigslist or ebay for around $20. 4MP is sufficient. All my photos on badcaps are taken with a Canon A80.

For lighting, since you live in Florida, you have all the lighting you need outside in the sun.

4) A SB140a diode is a schottky diode.

https://cdn.badcaps-static.com/pdfs/...780a9a5308.pdf

As such, it has a low forward voltage drop (straight from datasheet). So a reading of 0.2V and 0L is okay. Most diodes fail shorted.

5) When you can't find a training or service manual for your particular TV, try the models below and above it. Since LG makes many 50PK series TVs, you would have found this training manual with a bit of looking around.



In it, there is a in-depth section with pictures, describing how the SMPS works and the sequence in which things turn on.

It may not be exactly the same as the 50PK540, but it should provide valuable clues.

6) So let's review and try to make sense of all the readings. AC detect is 4.66. You have 5V and 17V which means the microprocessor has finished step 1 (see attached pictures).

Step 2 is to turn on M_ON (around 3.28V) which supplies 3 voltages including the Va and Vs. This is the key question that selldoor has been asking.

If M_ON is not generated (i.e. 0V), then Va and Vs will be 0.0.

This is step #7 on page 49 of the diagram.

7) Note there is a way to turn on the power supplies automatically, but requires a load to see if the SMPS is good and the main board is suspect. This is described on page 48 under the AUTO GND section.

8) I'm not a plasma expert at all, but all SMPS and main board interaction work more or less the same for any consumer electronic device.

[selldoor]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

I don't know guys... if that SB140a diode has a voltage drop of 0.2, to me that is bad. It should have 0.5 to 0.7V drop. Now if that's the little diode that's next to that IC301, chances are good for the IC to be bad too. These sets are known for that to go.

We have seen that -it is one of the parts in the repair kit. My thinking was that the IC is part of the PFC circuit and as he is measuring almost 400vdc on the BIG caps then the PFC is working so it should be ok, would you/anyone agree with that?

What we really need to know is after the Big caps how the VS & VA voltage
processed?

[CapLeaker]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

I don't know guys... if that SB140a diode has a voltage drop of 0.2, to me that is bad. It should have 0.5 to 0.7V drop. Now if that's the little diode that's next to that IC301, chances are good for the IC to be bad too. These sets are known for that to go.

[Michale32086]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

Sb140a
1005g

[Michale32086]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

Oh DOH!!

Lemme pull it and I'll check..

[selldoor]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

[QUOTE=Michale32086;522819]hehehehehehe

Marking like burns or the like?? Nope... The board looks in really good shape...

Noooooo! part numbers on the D304 diode?

[Michale32086]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

hehehehehehe

Marking like burns or the like?? Nope... The board looks in really good shape...

It seems I have a penchant for TVs with funky voltage readings..

https://www.badcaps.net/forum/showthread.php?t=42835

That one the voltages were ALL good across the board.. Still haven't figured that one yet either. That's the one that prompted me to buy the Rigol..

I'm thinking I will just replace the power PCB..

But I really learned a LOT by going thru this one...

Thanx a bunch to all who replied...

[selldoor]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

Sorry to be distracted.. Had my TV Scrap guy come in and bring me some new toys..

ERROR!!! You should have got them to take this one away!!!

I dont trust/understand the results from your meter perhaps I will have a snooze and see if anyone else can decide if its good or bad - either way
does it have any marking on it?

[Michale32086]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

Sorry to be distracted.. Had my TV Scrap guy come in and bring me some new toys..

[Michale32086]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

OK So it's not the problem??

[selldoor]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

OK, I de-soldered the D304...

When I use the meter in DIODE mode, I get 0L v one way and .20 v with a tone the other way...

When I use the meter in OHM mode, I get 20K ohm one way and .568M ohm the other way...

Hooray!!! Id say it is definitely bad

Any marking on it so we can establish what it is

EDIT Oh No!!! it isnt I was so excited I misread the .568M ohms - missed the M out

[selldoor]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

Looks like a bubble...

That is ok its just heat - in the other pic the solder joints didnt look good but was just the flash. They look fine

[Michale32086]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

Looks like a bubble...

[selldoor]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

Look at at the stuff they change out and check yours.

We have done that using another kit???

Michale cant make much of the traces but it does confirm there is nothing else
on the VS VA sockets .
Can you look on the back of the board - this section. Maybe the flash but
one side of that transformer doesnt look good?