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

The output voltage of IC303 is 1.7v

The input voltage of IC303 is -3.3v

Lemme get the pics.. That 8.1MP camera I got from my wife takes worse pictures than my phone..

[selldoor]

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

Ok - you need to remove it to check BUT maybe try a voltage test first?
When budm said someone had written a test guide he meant his guide
see here.
https://www.badcaps.net/forum/showth...999#post300999

He also has an excellent quide for 2 seconds to black written for monitors initially
but lots of tests relevant to many things. see here
https://www.badcaps.net/forum/showthread.php?t=10419 start at post19

Also the "Please post multimeter results" means for a fail as well as a pass.
Shows how to post them in the guide

[Michale32086]

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

OK, I checked IC301, IC302 and IC303...

On IC303.....

(and based on this link:http://www.learningaboutelectronics....tage-regulator

...the INPUT is shorted to GND..

IC301 and IC302 don't appear to have that issue..

[selldoor]

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

Yes well I thought as well -just clutching at straws and if you can get at it and are trying RCs tests may be a very very very slight chance that the IC1 is sending the enable signal to IC701 but it is not working so there will be 5 in but no 5v out. Is there a pin labelled
M_on on the on the connector from main board to power supply? If so is there continuity from it to the Pin6 on the IC701.

[Michale32086]

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

If you can get to the IC701 when it is all connected up perhaps test the voltage on the pins relative ground screw or ground pin on the IC think 1 and 5 should be 5v and the enable pin 3.29?

I may have read RC wrong, but I think he is saying that IC701 isn't the culprit, but rather it's IC1, the big heat-sinked component that is the Microprocessor.. The equivalent to IC701 on the PK750...

Which is a shame because IC701 on the PK540 is a LOT easier to swap out!

[Michale32086]

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

Good point. It's important to note that this unit was the victim of a lightning strike. There might be a whole host of scrambled components..

[selldoor]

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

Wow retiredcaps that was a lot of digging!
Think we may be on a hiding to nothing if power rush has scrambled the main processor That could also be why it switches on on plug in?. If you can get to the IC701 when it is all connected up perhaps test the voltage on the pins relative ground screw or ground pin on the IC think 1 and 5 should be 5v and the enable pin 3.29?

[Michale32086]

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

Oh well, the theory was sound!

Thanx RC...

I'll check all those when I get to the shop....

Your time and efforts are VERY appreciated...

[Michale32086]

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

So close.

So let's examine why IC1 is presumably not outputting M_ON at 3.29V.

As an fun exercise for Michale32086, stop reading right now. Go away in quiet area for 15 minutes and try to think why M_ON is zero. Then go read the next post.

Two possibilities come to mind after studying the diagram..

1. IC1 is not getting the signal from the IR Board/Touch Keypad

2. AC-DET is not sending the signal to IC1

Let me open the envelope and see what I've won!

[retiredcaps]

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

1) If M_ON is 0V from IC1, then there isn't much you can do because there is no part number and this is pretty much a complete board swap. BEFORE ordering a replacement, read #4.

2) If M_ON is 0V as measured on the SMPS, there is a small chance that there is a break in the cable from the main board to the power board. If M_ON is 3.29V on the main board connector, then you found the problem.

3) If M_ON is 0V measured on the main board connector, there is a chance that IC1 is outputting 3.29V, but the circuit path and/or the components between IC1 and the M_ON pin on the main board is bad.

You will note that the main board to SMPS connector is labeled P301. This implies that any components in the 300-399 is likely to be part of the same functionality.

For example, IC303 is a 3.3V voltage regulator. Hmm, M_ON is supposed to 3.29 and the regulator is supposed to output 3.3V.

If it is shorted to ground and in the circuit path as described above, then you will see 0V at the M_ON main board connector. I recall someone writing a well written easy to understand "How to test a voltage regulator" FAQ here.

IC302 is also a 3.3V regulator. Q301 and Q302 could also be used somehow in this circuit.

It only takes a couple of minutes to see if IC302, IC303, Q301 and Q302 are shorted or not.

Resistors in the R3xx range should also be tested to see if they are open circuit as vinceroger69 alluded to in post #123. L3xx are inductors and should measure as a short circuit (less than 1 ohm). Of course, C3xx are capacitors and could be bad as well.

Please post your multimeter results and not "it tests good" because the regulars have seen those types of comments before and the person doing the tests was dead wrong.

To know what is actually part of the circuit path, you have to use the continuity function on your multimeter and start with the M_ON pin and work towards IC1 since there is no schematic and we have no idea which pin on IC1 is responsible for generating M_ON. For each component in the path, you need to test it (back to chapter 7 of the book). Budm is good at tracing this stuff remotely. For me, I need the board in front of me.

edit: There may be another LG PJ model that contains a schematic, but it could take hours to find something identical to the 50PK540 main board?

If you are lucky, one of those components is bad and not IC1 meaning the fix is $1 or less.

4) If M_ON is 0V as measured on the SMPS connector, there is a chance that IC1 is sending 3.29V, but something on IC7101 on the SMPS is causing it to go to 0V. Obviously, by testing the SMPS with a load separately will help rule out this possibility.

So as you can see, you can't assume that the main board is bad because M_ON is 0V.

PS. I hate those pay service sites. If you can't it on the Internet, it is unlikely they will have it. They just use bots to go copying content from others.

[retiredcaps]

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

So close.

It took me over an hour to research and write this...

As I mentioned in post #92, I used the term microprocessor and wrote "It may not be exactly the same as the 50PK540, but it should provide valuable clues." Well, I didn't think I would be so correct after reading the progress.

Now that we have clear focused pictures of the main board (which should have been part of post#1 regardless what the problem is), it is obvious the 50PK750 and 50PK540 are not the same main board despite both have the 50PK prefix.

So, the next obvious candidate for the microcontroller on the 50PK540 is IC1 as selldoor initially guessed. If you stayed on this path and followed the philips part website, you would have found that IC1 is used in multiple LG plasmas including the LG50PJ series. PJ could be the precessor to the PK series?

Searching for "LG 50PJ training manual" leads to a training manual that more closely resembles the 50PK540 main board.

Looking at this new service manual, M_ON is still generated by IC1 on the main board and needs to be 3.29V. Once M_ON is received by the SMPS, IC 701 on the SMPS (back side) turns on VA and VS.

So the PK540 and PK750 do operate similarly, but the location of IC701 has been relocated between the two models for whatever reason.

So let's examine why IC1 is presumably not outputting M_ON at 3.29V.

As an fun exercise for Michale32086, stop reading right now. Go away in quiet area for 15 minutes and try to think why M_ON is zero. Then go read the next post.

[Michale32086]

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

Here is the full pic of the FSAA chip...

And the top part of that area...

The chip is approx tween the 100 cap and the USB port.

[Michale32086]

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

Thy will be done..

[selldoor]

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

Yes, but perhaps a few tests? I was starting to extract the info from the datasheet but it takes too long the attached shows the pin out and the marking.
here is a better link - direct to the datasheet

Still not real easy to follow - only the sections re 2019 and SOT form apply

I cant see how it all connects double sided board - perhaps that new schematic will help ( I have not looked at the 750 one may try later) Also that last picture was good!!! can you do a similar one showing 4 inches round the IC and the same from the top side of the board.
PIN 1 is where the DOT is

[Michale32086]

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

This site https://www.buyphilipsparts.com/mode...40?language=FR
lists all the parts ic701 page6
from that lg part no is EAN60223701
This site
https://www.buyphilipsparts.com/item...,analog_Switch suggests it is not in the 750

This site
http://www.electronicmarket.com.au/i...0-p-81393.html

suggests EAN60223701 is one of these
IC,Analog Switch (IC900)
[EAN60223701]

MIC2019YM6 2.5 to 5.5V 1MSEC 700USEC 0W SOT23-6 R/TP 6P 1 MICREL SEMICONDUCTOR INC.

which is one of these
http://www.digikey.com/product-detai...5-1-ND/1821755

Datasheet here


Of course it may be all a trick.

SD, is that part you found the DIGIKEY part??

If so, I can just order a new one as they are only a buck..

[vinceroger69]

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

I would check if pssible the resistors etc feeding the ic pins just incase ones gone open circuit etc

[selldoor]

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

Hmm well we think we know where the matches are
Has it got a number on it FK1 or FK2 (how appropriate) or something else then I can
see what the pins are. There may of course be nothing wrong with it but we can see if
at least there is voltage into it.

Got it FSAA

[Michale32086]

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

Such a small device for causing such a big problem..

[Michale32086]

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

Once again, I'll be deeped in sheet!!!

Ya found it!!!

NOW we're cooking with gas!!!

[selldoor]

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

We have a saying over here

" Should have gone to specsavers!"