LG 60PG3000-ZA faulty, mal discharge?

[py3m4n]

Hi everyone, first post and new to plasma TV repair. Repaired some LCD's Xbox 360's,PS3's and other various electrical and electronic appliances over the years. Hoping you clever bunch can point me in the right direction in fault finding this set as it's information overload at the moment learning about Plasma repair!!

Model number - 60PG3000-ZA
PDP Model number - PDP60X70223

When you first power the unit up from standby it will display mal-discharge? and large vertical white bands that will appear randomly across the screen. Normally when you first power it up it will revert to standby but after a few try's it will display the picture as described (see picture below) for around ten minutes, then revert to standby.



With Z-SUS disconnected the unit attempts to display the large white vertical bands but these are essentially expanding blotches of mal-discharge (pictured below) that attempt to fill where the white bands were previously shown with both the Z-SUS and Y-SUS connected. The rest of the display other than these areas is black. The unit will sometimes revert to standby when in this condition, other times it will not.



With the Y-SUS disconnected the unit has a dark screen although the green power LED (on front of TV) remains steady and does not revert to standby.

Tried bridging the AUTO_GEN with the LVDS cable disconnected to see if the self test card would appear. Test card does not appear, symptoms remain the same.

Only tested one source and that was HDMI. Got sound, but picture essentially remained the same, except with vertical multi-coloured lines appearing across the width of the screen.

All voltages on the power board test good.

Voltage settings:

5v/Va:60/Vs:192
N.A/-190/115/N.A/100

Voltages read:

5v/Va:60/Vs:185

I realise that Vs reads 6v lower however when attempting to adjust the PSU Vs pot to 192 the unit will shut down, and I was not particularly keen to be messing around with this any further, as I don't see this playing a part in the current fault.

There is a resistor on the Y-SUS for testing the -VY voltage. When I attempt to check this I can not get a stable reading. I can not locate where to take the VSC voltage on the Y-SUS.



Seems to my like the Y-SUS is were the problem lies, going by the erratic reading on the -VY resistor check point. However, I have read that there are ROM firmware issues with these LG models, that when updated, can solve mal-discharge problems of this nature, and I would like to rule this out as a possibility before continuing, as getting the FW to update is not likely and would mean purchasing a new control board. Not wanting to do this if the problem is the Y-SUS...


That leads me neatly to why I have posted looking for any advice from some of you repair vets on further testing to locate which board (or potentially multiple boards!) that are causing me sleepless nights!

LG60PG3000 Service Manual.

http://elektrotanya.com/lg_60pg3000.pdf/download.html

[rayrod81]

Re: LG 60PG3000-ZA faulty, mal discharge?

The firmware has nothing to do with your problems and the Y-sus and/or Y-buffers are bad. The unstable -Vy pretty much confirms this. It could be a bad buffer causing this or it could be a buffer coupled with a bad Y-sustain. You will need to check the boards for shorted mosfets and blown resistors. It could be a simple repair or you will have to spend the money and buy replacement boards.

[py3m4n]

Re: LG 60PG3000-ZA faulty, mal discharge?

Thanks for the fast reply rayrod81, really appreciate it.

Done some more tests today with the Y-SUS.

I disconnected the the Y drive buffer boards individually and there is no change in the -VY or VSC voltages at the test points on the Y-SUS, they are still unstable. (I found the VSC, it was staring me right in the face the whole time, the usual...) My question here is from doing these test how sure can I be of ruling out the Y buffer boards?

I have checked the main fuses and all the 125v SMD fuses I can find on the Y-SUS and they all test good.

Can anyone point me in the right direction of what I should being doing next if I want to have a go at fixing this on a component level?

[rayrod81]

Re: LG 60PG3000-ZA faulty, mal discharge?

Did you test with both buffers disconnected? As for the Y-sus you are probably looking at a bad regulator, leaky diode, and/or bad caps.

[py3m4n]

Re: LG 60PG3000-ZA faulty, mal discharge?

Yup, tested with both disconnected, -Vy and VSC still unstable. Pulled the large blue capacitors and ones in surrounding area, all have acceptable uF and ESR.

My gut is telling me not to waste my time and energy pulling any more caps as a visual check shows no signs of deterioration, and concentrate on the six regulators that are under the center heatsink. There is a mild buzzing coming from both the Y-SUS and Z-SUS but around the center heatsink (as best I can tell) on the Y-SUS the buzzing is higher pitched.

[pecrie]

Re: LG 60PG3000-ZA faulty, mal discharge?

Just started to investigate on some lg plasmas.What I found was ,that Vsc ,set - up and set - down voltages ,and also the Z (board) bias ,must be adjusted (measured) ,with an oscilloscope of at least 200 Mhz.

So ,it`s normal ,that you don`t get a steady reading ,when connecting a DMM ,to these test points.


good luck

[tom66]

Re: LG 60PG3000-ZA faulty, mal discharge?

Just started to investigate on some lg plasmas.What I found was ,that Vsc ,set - up and set - down voltages ,and also the Z (board) bias ,must be adjusted (measured) ,with an oscilloscope of at least 200 Mhz.

So ,it`s normal ,that you don`t get a steady reading ,when connecting a DMM ,to these test points.


good luck

The Vsc voltage should be fixed as it is generated by an SMPS.

The Vscan voltage(s) are what need to be measured with a 200 MHz oscilloscope. That being said, I did have success using a 20 MHz analog oscilloscope (which is much cheaper than a 200 MHz one), but it was difficult to measure the exact timing.

[pecrie]

Re: LG 60PG3000-ZA faulty, mal discharge?

@tom66

you are right.But what do you call ,the Vscan voltage??

[tom66]

Re: LG 60PG3000-ZA faulty, mal discharge?

@tom66

you are right.But what do you call ,the Vscan voltage??

The Vscan voltage is what the sustain board generates. You need an oscilloscope to measure it as it is not fixed.

The Vsc or Vscn voltage is fixed and should be stable to within 1V, preferably 0.1V. It's usually marked on the board.

Is this a 60" set? In which case I would go ahead with replacing the sustain board entirely, as it would probably take a long time to track down the exact fault.

[pecrie]

Re: LG 60PG3000-ZA faulty, mal discharge?

yes ,I was referring to that ,which they say has the waveform (Y wave form) testpoint ,on the y driver board.But I did mixed it up ,with the Vsc ,which is on the Y - sus board.

No ,it`s just a 42" lg plasma.But I think ,I might have found it.Put in a new Y-sus board ,cause the repair man ,had taken out the IPM hybrid module ,from the Y-sus.He said it was the cause ,of no picture (black screen) with sound.

With the new board ,I get a bad picture.Mal discharge and dark areas.So ,I suspect that the Z-sus board`s IPM ,is bad also.

I did the test measurements on that IPM ,and it was not good.So ,I`m trying ,to desolder the IPM from the board.But it`s quite a job.Need a heavier soldering iron.
Bought the new IPM`s ,already some time ago ,on ebay.

So ,if I have it replaced ,I think it`s good to go.Bought this set from someone ,who didn`t wanted to repair it.

I also have another set ,but did not have had time ,to investigate.The seller told me ,that all of a sudden ,the picture was gone.On a first quick check ,I noticed ,that one of the fuses ,on the Y-sus board ,has blown.

Makes me suspect a defective IPM ,on that Y-sus board.If the Z-sus is oke ,I can put that in the set ,I am working on now.

They are a LG 42PC1R.Got the service and training manuals ,but no schematics.

We`ll see ,how it goes

[py3m4n]

Re: LG 60PG3000-ZA faulty, mal discharge?

With the above said, then I would be better off replacing the Y-SUS and both buffers to solve the problem I have? as I can't expect to get a stable reading with a DMM from the -Vy and Vsc test points on the Y-SUS, I need to use a 200Mhz oscilloscope. (always learning, wonderful thing the internet!)

[rayrod81]

Re: LG 60PG3000-ZA faulty, mal discharge?

You do not need an oscilloscope to check -Vy or Vsc. A good DMM will work. An oscilloscope is only needed to check and adjust the waveform coming off the Y-sus. There is a problem with the Y-sus if the voltages are not stable so it does need to be replaced. The buffers are also most likely bad based on your pictures of the problem.

[py3m4n]

Re: LG 60PG3000-ZA faulty, mal discharge?

That's what I was thinking when reading, going by a plasma fault finding flow chart I have. It made no mention of an oscilloscope, although it made no mention of an DMM, but it read like your just checking the voltages, not looking for waveforms. Cheers for clearing that up rayrod81.

Reading the posts back I think I can see how I got confused.

[pecrie]

Re: LG 60PG3000-ZA faulty, mal discharge?

@py3m4n


I`m not sure if you have a training manual ,of an lg plasma tv.In some there are images of the Y - sus waveform.

When I had replaced the Y-sus board ,I had a bad picture.So ,I thought that the Y-driver board was also bad.Ordered a second hand one ,from an (reputable) English repair shop.
He`s selling parts ,and advertising for tv repairs.At that time ,I didn`t had the second set ,so could not swap parts.

Put it in ,and still the same bad picture.That`s when I thought ,that the Z-sus board ,could be the cause.
So ,I measured with the DMM ,the resistance , on the IPM of the Z-sus ,according to the training manual.Still hasn`t got it desoldered.

Will check the Z-sus of the second set ,than swap it out.

You can measure and adjust -Vy ,Vsc and Zbias ,with DMM.According to the panel label

So ,it could be ,that only the Y-sus is bad ,in your tv.

[py3m4n]

Re: LG 60PG3000-ZA faulty, mal discharge?

@Pecrie

I do have a training manual for LG plasmas.

At the moment it's finding the time (isn't it always the case) to sit down and pull components to try and find out what parts on the Y-SUS are faulty, as you will all know yourself it isn't really something that you can do when you have a spare 5 minutes, as you tend to end up there for hours, lol. What I really need to do is get a better understanding of circuit design and following how the voltage/current is distributed across the board making it easier to fault find. With most LCD's I have repaired, finding which board is definitely at fault has been fairly simple and there have been a few where I have replaced components but for the most part they have been brought back to life by "board swapping".

I have looked into just buying replacement boards but even getting 'recycled' boards for the 60PG3000 is difficult here in the UK. I have seen them on Shopjimmy.com but getting the buffers and Y-SUS will be expensive and I will likely also get hit with import tax on them. I hate the thought of replacing multiple boards when all that I possibly needed to do was replace some bad regulators, resistors, diodes etc. or even some IC's. I am pretty experienced with a soldering iron and hot air gun at this point after the number of Xbox 360's I have repaired in recent times, be it either through reflowing them or reworking the BGA's, replacing FET's, ethernet IC's, or even replacing SMD's like capacitors (not fun!) So I am always up for a challenge.

I am pretty positive there is a fault on the Y-SUS itself, it's just tracking it down without pulling all the components that is my preference. So I am spending more time reading than anything else.

What I will say though, is either way, whether I replaced boards or happen to track down any faulty components (even if replacing them doesn't bring it back to life) I will keep this thread updated letting you all know how I get on.

edit - Also meant to say, let us know how you got on with your TV Pecrie and what exactly you did to bring it back to life!

[pecrie]

Re: LG 60PG3000-ZA faulty, mal discharge?

py3m4n

Well here`s an update.Still have to buy a heavier soldering iron ,or one for smd mounted devices.Anyway ,the Z-sus with the bad IPM ,is waiting for replacement.

So ,like you said ,it`s to find the time ,to get yourself to start troubleshooting ,on the set.I took out the Z-sus from the second set ,and it looks like new.
It could be ,that the second set ,is not too old.Checked the IPM for short ,or broken diodes.

It all measured ,according to the manual.So ,I put it in the first tv ,I am working on.But didn`t connect it ,to the power.Also all other connectors ,which go this board ,I left disconnected.

Then I checked Va ,Vs ,5.5V on the PSU.Checked -Vy and Vsc ,on the Y - sus board.Because it was a new board ,I didn`t expect ,very much different voltages.They were oke.

When I powered the tv ,of course ,only the right side half of the screen (when in front of it) ,showed some maldischarge ,with black areas.

Finally connected everything ,to the Z - sus board ,and I got a white screen.That is ,there was no input signal.Connected the antenne cable ,and we had a nice picture.

This is the first plasma set ,ever ,that I owned.Have never opened one before this.But like you ,I did a lot of reading in the manuals ,watching You Tube movies ,and reading on several forums.Which all have been a great help.

Only thing ,I noticed ,that when I hit the power button ,on the remote ,the set will not turn on.But it did ,some months ago ,when I was first fuzzling with it.I can switch it on ,with the power button ,on the set.

But everything else on the remote is working.Like changing channels ,volume up and down ,menu etc.A little strange.

Maybe someone knows ,what can cause this.I had the set on for several hours ,seeking channels ,and so on.All in all ,the picture quality ,isn`t bad.It`s not an HD tv.
Though it`s HD ready ,so I think it can play HD movies.

For a first time repair ,I think it is not too bad.Now find time ,for the second one.
Yes ,I understand ,that you want to get to the heart of it.But without any schematics ,I don`t have them ,it is gonna be long road.

As long as ,you don`t need the set ,to watch ,then that`s not a problem.By the way ,I bought the Y-sus board in Germany.

[py3m4n]

Re: LG 60PG3000-ZA faulty, mal discharge?

Decided to pull some more components and eventually found two bad FET's (see picture, circled in red) they read 27N25. After some searching around I am pretty sure their full title is FQB27N25TM, problem is they are now obsolete and I am having difficulty finding an equivalent. I have been searching around on Digikey and Farnell but I am not confident enough or sure enough of which ones would be a like for like replacement. Any help would be greatly appreciated!

[tom66]

Re: LG 60PG3000-ZA faulty, mal discharge?

Any of these will probably do: http://www.fairchildsemi.com/sitesea...t_number&text=

Just select the one you want or can get.

Make sure to match the pin outs but for most power MOSFET's they are the same.

[py3m4n]

Re: LG 60PG3000-ZA faulty, mal discharge?

Cheers tom66. Ordered some FQB34N20L today, hopefully have them soon.

[py3m4n]

Re: LG 60PG3000-ZA faulty, mal discharge?

Little update on this T.V. Recently got round to replacing the Y-SUS, Z-SUS, and main logic board (did it all in one go) and the problem still persists. Just wondering if those of you experienced with plasma repair would at this stage be assuming the panel itself is bad?

Cheers, Davie.