LG 42" Plasma Colored Vertical Lines and No Video, No Menus

[e079260]

Hi - see attached photo of LG model DU-42PX12X with vertical pinstripe lines across the full screen changing colors. No video, so no access to menus, so unable to test if sound works.

Can anyone tell from the attached picture if this is most likely caused by which faulty board:
* Ysus
* Zsus
* Control board
* LVDS board
* or some other most likely cause?

Fuses, caps, driver chips appear good and no signs of distress in the set.
I infer that that the slab panel is good from the bright full screen consistent picture, the driver chips are good, and the power voltages are probably good. What boards in what order should I replace?

Thank you for any advice you can offer,

Michael
(an electrical engineer, but little test equipment and new to plasma tv so limited to board replacements, but hopeful I can fix this TV

https://www.badcaps.net/forum/attach...1&d=1282249843

[PlainBill]

Re: LG 42" Plasma Colored Vertical Lines and No Video, No Menus

Hi - see attached photo of LG model DU-42PX12X with vertical pinstripe lines across the full screen changing colors. No video, so no access to menus, so unable to test if sound works.

Can anyone tell from the attached picture if this is most likely caused by which faulty board:
* Ysus
* Zsus
* Control board
* LVDS board
* or some other most likely cause?

Fuses, caps, driver chips appear good and no signs of distress in the set.
I infer that that the slab panel is good from the bright full screen consistent picture, the driver chips are good, and the power voltages are probably good. What boards in what order should I replace?

Thank you for any advice you can offer,

Michael
(an electrical engineer, but little test equipment and new to plasma tv so limited to board replacements, but hopeful I can fix this TV

https://www.badcaps.net/forum/attach...1&d=1282249843

It's a little early to be replacing parts. The first step would be to measure the outputs of the power supply. Most of them are identified by voltage. There is a label on the back of the panel which identifies the voltage which are specific for the individual panel. Check those too.

The next step is to do a little learning. Google scribd LG plasma training manual and also scribd DU-42PX12X service manual. These searches should bring up at least three manuals. There should also be a model number for the plasma panel, either on the panel or you can find it in the service manual. Google THAT number and service manual.

One little hint. If you can find the service manual for the panel, there may be a set of switches on the main control card (it's behind the signal panel) that allows you to put the panel in service mode. This bypasses things like tuner, video processor, etc.

PlainBill

[e079260]

Re: LG 42" Plasma Colored Vertical Lines and No Video, No Menus

Hi PlainBill - thank you for your advice. I have reviewed the available manuals. From the symptoms I think the voltages are OK and will confirm that. Another clue: maybe narrowed down to the Main LVDS board OR the Controller board, since if I disconnect the signal cable between these 2 boards (set unpowered) the colored vertical lines across the display do not appear and the plasma display still primes (comes on blank) upon power up. Also, this was a sudden one way failure i.e. not time or heat related, so I suspect a board failure. Can you tell from this added info which board is most suspect --- the Main LVDS board or the Control board? I think the signal flow is from the Main LVDS to the Controller, so logically it seems to me the bad signal is coming from the LVDS - do you agree?

Many thanks,
Michael

[PlainBill]

Re: LG 42" Plasma Colored Vertical Lines and No Video, No Menus

Hi PlainBill - thank you for your advice. I have reviewed the available manuals. From the symptoms I think the voltages are OK and will confirm that. Another clue: maybe narrowed down to the Main LVDS board OR the Controller board, since if I disconnect the signal cable between these 2 boards (set unpowered) the colored vertical lines across the display do not appear and the plasma display still primes (comes on blank) upon power up. Also, this was a sudden one way failure i.e. not time or heat related, so I suspect a board failure. Can you tell from this added info which board is most suspect --- the Main LVDS board or the Control board? I think the signal flow is from the Main LVDS to the Controller, so logically it seems to me the bad signal is coming from the LVDS - do you agree?

Many thanks,
Michael

Let's make sure we are using the same terminology. Some manufacturers seek to confuse everyone, others use distinct terminology.

I prefer Philips' terminology. They call the board with the HDMI, DVI, DB15, RCA connectors and the tuner the small Small Signal Board (SSB). LVDS (for Low Voltage Display System) would also be an appropriate acronym.

Usually hidden behind the SSB (or LVDS) is a card that takes the signal from the LVDS and routes it to the X, Y, and Z cards. This is sometimes described as the main control card or main logic card.

The primary signal flow is from the LVDS to the MCC (MLC). There may be some status lines; I'm not sure. Certainly if you disconnect the cable linking the two and the problem clears up you should concentrate on the LVDS. As an additional test, in some cases the MLC has switches or jumpers which can be set to put the display in test mode.

As far as the LVDS, the service manual by the TV manufacturer often covers this in exquisite detail. I would certainly go so far as to make sure all voltage regulators on this card are working properly.

PlainBill

[e079260]

Re: LG 42" Plasma Colored Vertical Lines and No Video, No Menus

Hi Bill, here are some results for your consideration and advice if you please:

The panel label is:
PDP42X2
Va: 60 Vs:200
80 / -200 / 120 /NA / 90

So, following are the (spec) voltages, the actual measured voltage, and V adjusted in some cases:
(12) = 11.9
(3.4) = 3.318 adj to 3.39
(5.0) = 5.1
(6.0) = 5.93
(19) = 18.81
Va (60) = 60.9
Vs(200) = 185 at power supply, unable to adjust up to min. spec of 195 using PS potentiometer. Also, why is there a separate Vs pot on the Ysus board?
Vzbias (90) = 99.6 adj to 90.1
-Vy (200) = 210 +/- 2 adj to 198 +/-3

Also, I had the oppor. to swap/try (presumed) good Ysus, Zsus, LVDS (front signal board), and MCC (Control Board between LVDS and the Panel) boards and the same maldischarge symptom persisted throughout, specifically:
* Well lit display with vertical multicolored pinstripes flickering (see photo attached above)
* There is proper sound
* Tuner does change channels using cable tv signal input
* There does seem to be menus and video behind the flickering pinstripes but not readable or watchable
* Remote control works to turn on/off, change channels, etc. but menus and video are barely visible through the pinstripes maldischarge

So, will a +10v higher Vs clear up this display? is the power supply board the problem?

Thank you in advance for your thoughts,
Michael

[PlainBill]

Re: LG 42" Plasma Colored Vertical Lines and No Video, No Menus

Hi Bill, here are some results for your consideration and advice if you please:

The panel label is:
PDP42X2
Va: 60 Vs:200
80 / -200 / 120 /NA / 90

So, following are the (spec) voltages, the actual measured voltage, and V adjusted in some cases:
(12) = 11.9
(3.4) = 3.318 adj to 3.39
(5.0) = 5.1
(6.0) = 5.93
(19) = 18.81
Va (60) = 60.9
Vs(200) = 185 at power supply, unable to adjust up to min. spec of 195 using PS potentiometer. Also, why is there a separate Vs pot on the Ysus board?
Vzbias (90) = 99.6 adj to 90.1
-Vy (200) = 210 +/- 2 adj to 198 +/-3

Also, I had the oppor. to swap/try (presumed) good Ysus, Zsus, LVDS (front signal board), and MCC (Control Board between LVDS and the Panel) boards and the same maldischarge symptom persisted throughout, specifically:
* Well lit display with vertical multicolored pinstripes flickering (see photo attached above)
* There is proper sound
* Tuner does change channels using cable tv signal input
* There does seem to be menus and video behind the flickering pinstripes but not readable or watchable
* Remote control works to turn on/off, change channels, etc. but menus and video are barely visible through the pinstripes maldischarge

So, will a +10v higher Vs clear up this display? is the power supply board the problem?

Thank you in advance for your thoughts,
Michael

I appreciate the confidence you have in my knowledge, but this is beyond my experience. I have the same model TV, but would face the wrath of wife if I suggested removing it from the wall and misadjusting the Vs voltage to see the results. My gut feeling is the power supply is not the cause; rather the panel itself is defective. Wizard would be much more likely to understand the problem and propose a solution.

PlainBill

[e079260]

Re: LG 42" Plasma Colored Vertical Lines and No Video, No Menus

Hi PlainBill - please do not incur any marital wrath over my LG plasma problem - LOL. Yes, anyone reading this forum knows of Wizard. I offered Wizard a note inviting him to visit this thread and to opine, so awaiting his expert input. Maybe you can let him know he is really needed here

Thank you again for your all your help to date. I am really stumped. Since the screen is bright with some video behind a bright random pinstripe image, I tend to infer the power supply and the panel must be good? If anyone can explain how a 10v (5%) deficiency on the Vs power or a bad tube could exhibit these symptoms please enlighten me.

Still learning,
Michael

[Wizard]

Re: LG 42" Plasma Colored Vertical Lines and No Video, No Menus

You diagnosed a bad mainboard. Philips is bit common with sneaky faults especially with mainboards.

You'll need to change the power supply if you can not raise the Vs as specified by the panel's sticker.

Once fixed, if you get sparkles, adjust either way very slightly on Vs and Va till sparkles disappears.

Cheers, Wizard

[e079260]

Re: LG 42" Plasma Colored Vertical Lines and No Video, No Menus

Hi Wizard - thank you, I will replace the PS and report back. I swapped main boards already and the same exact symptom persisted, so hopefully that means it comes down to the PS.

Cheers,
Michael

[Wizard]

Re: LG 42" Plasma Colored Vertical Lines and No Video, No Menus

Stop stop!!

PS is working properly to get far to that.

Cut your losses. Since you have swapped: LVDS cable, logic board, mainboard. The Y-SUS and Z-SUS is not the problem as you can see they worked.

Follow the logic do you? If you spot something you missed tell us.

Cheers, Wizard

[e079260]

Re: LG 42" Plasma Colored Vertical Lines and No Video, No Menus

Hi Wizard and All,

I am approaching wits end! You are right, the PS is OK, confirmed by swapping another (trial avail. at no cost, fortunately). I also swapped another LVDS main logic board with no change in the symptoms. Please note that I have not changed the LVDS CABLE as you may have thought, and I have not suspected the cable itself since it is mainly a mechanical part, and the failure mode was sudden.

However, when I unplug the LVDS cable between the main logic board to the control board, the vertical pinstripes go away and I get the mostly dark screen with some random sparkles as you described. Which is why I have mostly suspected the main logic board, but the original and 2 swaps all exhibit the same symptom!

All these boards seem to be confirmed good, at least no change in the symptoms: Power Supply, Main Logic board, Control board, Ysus, and Zsus. Since the panel itself primes and exhibits sparkles instead of pinstripes when the LVDS cable is opened (between the main logic and the control boards) I infer that the entire PS/panel/Y/Z high voltage and Control boards are all functioning properly?!

I am still in this a bit further for E&E (education and ego) so not quite ready to surender. So, what ELSE could be problem? I did find this info attached from Hitachi, which looks very similar to my display, except my "band" of digital noise is vertical instead of horizontal, and my band moves around and changes width when I toggle the menus, etc. The band seems to be where the text would normally display. The Hitachi info suggests a driver chip is bad -- could this corrupt the entire display with digital noise and noisy bands 4-6 inches wide? What else could be the problem?

In my set, the Y driver chips (on the left side of the panel facing the rear) all appear normal. I cannot access the X chips along the bottom of the panel since they are under heat sinks and some framing. Any ideas to narrow down this problem? Maybe LVDS cable? Or a driver chip -- Y or X?

Thank you in advance,
Michael

[mbates14]

Re: LG 42" Plasma Colored Vertical Lines and No Video, No Menus

one thing you have NOT replaced or tried to swap out. thats the Y buffers. ive seen Y-buffers do stupid crap like that.

however, its more "controllable" faults.

[Innov8tive1]

Re: LG 42" Plasma Colored Vertical Lines and No Video, No Menus

Any new progress? I have been working on a LG RU42PX11 (PDP42V6 panel) on and off over the summer. I too am a former TV tech with no plasma experience. I am finding the process of troubleshooting not only frustratingly slow but also not very precise. Perhaps with experience one would get good at diagnosing faults but as for me I will not EVER tell anyone I'll look at their plasma TV again! I did tell them when I started that I could not make them any promises as I had very limited knowledge.

Anyway, back to the story...........the set in question acts exactly as you describe the one you are working on. With cable hooked to the RF input there are vertical lines flashing all over the screen which seem to change with the video that is being input. The audio is fine and channels change like they should. In the space between show and commercial the screen goes blank and as soon as the commercial starts so do the flashing vertical lines. The fault mode for this set was also sudden and not related to heat or time as far as I can determine.
I have tried replacing the "digital board" ( I know there are millions of names used by different people) and the one behind it which I was calling the video or processor board. Both parts from E-bay (yeah, it's getting pricey!) but one I was able to return. Problem with used parts with unknown origin is that you are not sure if you have put someone else's problem into your set.
The power supply is making a pronounced humming almost a squealing noise like it is being loaded down but when I disconnect the LVDS to Controller cable the noise goes away.

I know I'm not helping much here with the original problem but I'm at my wits end. These folks want their TV back and if I don't fix it, I'm out the money for the boards I put in!

[PowerAmpFreak]

Re: LG 42" Plasma Colored Vertical Lines and No Video, No Menus

Any new progress? I have been working on a LG RU42PX11 (PDP42V6 panel) on and off over the summer. I too am a former TV tech with no plasma experience. I am finding the process of troubleshooting not only frustratingly slow but also not very precise. Perhaps with experience one would get good at diagnosing faults but as for me I will not EVER tell anyone I'll look at their plasma TV again! I did tell them when I started that I could not make them any promises as I had very limited knowledge.

Anyway, back to the story...........the set in question acts exactly as you describe the one you are working on. With cable hooked to the RF input there are vertical lines flashing all over the screen which seem to change with the video that is being input. The audio is fine and channels change like they should. In the space between show and commercial the screen goes blank and as soon as the commercial starts so do the flashing vertical lines. The fault mode for this set was also sudden and not related to heat or time as far as I can determine.
I have tried replacing the "digital board" ( I know there are millions of names used by different people) and the one behind it which I was calling the video or processor board. Both parts from E-bay (yeah, it's getting pricey!) but one I was able to return. Problem with used parts with unknown origin is that you are not sure if you have put someone else's problem into your set.
The power supply is making a pronounced humming almost a squealing noise like it is being loaded down but when I disconnect the LVDS to Controller cable the noise goes away.

I know I'm not helping much here with the original problem but I'm at my wits end. These folks want their TV back and if I don't fix it, I'm out the money for the boards I put in!

I agree, besides there must be some kind of warranty of repair from the customer's point of view. If you get a broken plasma into the shop, you find a faulty Y-SUS. Replace (perhaps getting one from E-bay with unknown status and history) finally get the TV up and running. Back to customer for one week, screen black again, customer not satisfied, return to shop. You find the Y-SUS blown again, AND now also the Y-buffes seems toast. What will you do? Search for another E-bay board? Replace the IPM which is hell of a work without the proper tools, search and pay for new Y-buffers...
The story can be quite costly for the poor repairman without *exact* knowledge about specific PDP panel/chassis he's working on.

[modmom32]

Re: LG 42" Plasma Colored Vertical Lines and No Video, No Menus

I am not a repair person, intact I am only a stay at home mom. I did take ITT course for electronics and graduated even but still, just the same, I have forgotten most of that.... I have a RU 42PX11 ED plasma with the same issue. I just replaced the y-sus board no change. So my board is ok I guess and so is the one I bought. However..... I did nothing to buffers. Or x-sus board... Off top of your heads though you would agree ysus , right?

[Innov8tive1]

Re: LG 42" Plasma Colored Vertical Lines and No Video, No Menus

I replaced the Ysus on the one I was working on too and no change. I don't think it's Y-sus related. With Ysus faults I think you would get horizontal lines, not vertical ones.
I did some playing with this one as I really had nothing to lose and when I disconnected some of the ribbon cables on the lower side, I got corresponding vertical blank spots.
I was always thinking of it in terms of CRT sets where your horizontal deflection would cause side problems and vertical deflection would cause mostly top but sometimes shrunken picture top to bottom but the way a plasma set works is completely different!
I have come to the point where I'm done throwing money away trying different boards. It may even be a problem with the panel I don't know. I metered the Ysus driver boards as well as the MCC boards as described in one of the plasma troubleshooting/service manuals that was mentioned above and found no fault in any of them. For me, I'm done with it, I can't spend any more time and money on it. Unfortunately I will chalk it up to a very complicated and unreliable technology that is designed to fail. I have a very low opinion of plasma TVs because of this and as such I will never buy one. There are too many stories of 3-4 year old sets cooking themselves to death and causing catastrophic failure. Limited (and often expensive) parts make these non HD sets completely impractical to repair unless you have a parts donor set with a broken panel or other known fault.
If someone on here does find a fix for it or can confirm what the fault is, I might consider trying again but as for now I have a really bad taste in my mouth. I have an 18 year old CRT set in my shop that still has a killer picture (panasonic superflat that hasn't been run to death) and even though it's not high def I still consider it a worthwhile tv. How many plasma sets will run that long? My guess is not many. Sad that so many CRTs are going into the landfill and being replaced with newer technologies with shorter life spans.
Rant off.........I know this isn't productive to the cause of fixing sets but it feels good to get it off my chest.

[PowerAmpFreak]

Re: LG 42" Plasma Colored Vertical Lines and No Video, No Menus

I couldn't say it better myself and couldn't agree more. I've not dealt much with plasma, but the 6 months I've been involved with quite a few. Repair rates increase, but I'm on a point where I must make a decision. I'm the curious guy who like technologies and could waste some time from time to time, just for curiousity to fix a problem. Even if this exceed all limits in work time.
My question is: If I take in customer's plasma TV in my shop I must have reliable sources of spareparts. This is to have the ability to give my customer a repair warranty which usually is 3 months. This means, I cannot search for boards on E-bay with completely unknown status and history. This may really end up where I don't want to be. I place the big bucks in spareparts without getting the thing up and running. I cannot suck this out from my customer either. But plasma repair, is basically a module swapping paradise, if working modules on hand, it's very easy to repair. It's made to repair fast under warranty period, even by home repair visits. Just bring a set of modules for that particular set. If the panel is OK of course.
It's a different story for us trying to earn some money doing "after warranty" repairs. Then it appears the spareparts has gone out of production, no longer available and all that horrible story. This is not only about plasma, I've two identical Samsung LCD TV's in need of a new mainboard both of them. They are three and a half year old, the mainboard is no longer available. What a joke. The market has changed so much since our CRT repair period. The producers of plasma and LCD TV's must do this way to survive, the prices are pushed down so much that a customer must replace the TV often.
I bet there are NO plasma or LCD on this earth which will survive for 18 years.
Just stick your nose close to a running plasma TV, the electronics works really really hot. This will of course, limit the lifetime of power semiconductors and capacitors on the board. Recently I got a Philips 50" model 50PF7320/10 (see another thred in this forum) repaired and actually put at home. My kids are happy and my wife loves it. But each time I power it on, my heart beats an extra beat. With increased knowledge about Plasma technology, I cannot help to feel this is quite unreliable stuff.

[monkeybytes]

Re: LG 42" Plasma Colored Vertical Lines and No Video, No Menus

Anyone come up with a solution? I have an RU42 with the exact problems....havent been able to run down the solution to this problem anywhere...