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Old 01-17-2012, 05:12 PM   #1
tom66
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Default A guide to fixing/troubleshooting some common plasma TV problems

This guide will attempt to help you diagnose some common problems with plasma TVs. It applies to most manufacturers of plasma TVs.

Some background about plasma TVs (feel free to skip)
Most plasma TVs are made by three major manufacturers. Samsung, LG, and Panasonic are the most common. There are some older manufacturers, including NEC, Hitachi, Pioneer, etc. which are no longer in the business of manufacturing of PDPs.

A PDP is essentially a module sold to a manufacturer. The PDP comes with the glass panel which contains a mix of noble gases. It is vital that this panel is not damaged as a crack may lead to the gases escaping, making the panel a very expensive and very heavy paperweight. (It is NOT possible to re-gas a PDP module, at present at least.) The PDP also comes fitted with the Y-buffers, Y-sustain, Z-sustain, control board and X drivers. In some cases, it may come with a power supply.

The PDP is manufactured by one of the larger manufacturers. If, for example, you buy a store-brand plasma TV, the retailer has made a contract with a company somewhere in the Far East (probably...) to make a Plasma TV for them. This manufacturer will buy the PDP module from the PDP manufacturer (LG & Samsung usually sell modules - Panasonic doesn't usually) and put some other components with it such as the main board and a power supply, and put it in a case, then ship it off to the retailer.

If you buy a plasma TV from one of the bigger manufacturers that make their own PDPs, then the manufacturer has supplied their own boards and put their name on it.

Boards in a plasma TV
A plasma TV contains at least:
  • Y-buffer (sometimes in two parts, a Y upper and Y lower). This connects to the Y-sustain.
  • Y-sustain (Samsung call it an Y-main and Panasonic call it an SC board). This is almost always on the left of the screen when you look at it from behind.
  • Z-sustain (Samsung call it an X-main and Panasonic call it an SS board). This is almost always on the right from behind.
  • Control board (sometimes called T-con and not to be confused with LCD T-con boards). Often buried under a main board.
  • X driver - sometimes fitted to the control board or integrated on it.
  • Power supply
  • Main board / AV board / Tuner board - the board with the input connectors, antenna etc. on it
From now on I will be using LG terminology as it is more familiar to me.

Tools of the trade
I highly recommend you have at least:
  • A digital multimeter. An analogue multimeter will not suffice.
  • A Phillips-head screwdriver
  • Patience
If you have an oscilloscope with a rated minimum of 400V inputs and a 10X probe that is also very useful.

DANGER: A plasma TV has voltages in excess of 380V on some connectors. The capacitance on the Vsus bus (>4,500F) is easily enough to jump-start your heart and can power the TV for half a second with a fully white picture, that's over 200 joules. UNDER NO CIRCUMSTANCES TOUCH ANY PART ON THE BACK OF THE TV WHILE IT IS RUNNING OR SHORTLY AFTER POWER OFF! I highly recommend you have someone around you watching you while you service your TV in case you do make a mistake.

Identifying the fault
The first step is to identify the fault in question. Does the TV power up? Is there a picture? If there is a picture, is it clear? Are there any signs of "sparklies" or image retention on the screen?

Were you using the TV when the fault occurred? Was it gradual, or did it suddenly happen? If the TV doesn't give a picture any more, does something smell like burning plastic? Was any smoke emitted from the back of the unit?

[Continued below.]
Attached Images
File Type: jpg DSCN6915.JPG (97.3 KB, 1850 views)
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Please do not PM me for help and support. Questions belong on the public forum.

70 LED/LCD TVs, 5 monitors, 26 plasma TVs, and 2 AVR 6.1 amplifiers saved from the dump!
Totally free service manuals database: http://www.toms-service-manuals.com/ (Contact me for requests or contributions.)

I have successfully fixed (from best --> worst build quality):
1 Pioneer KURO 9G, 10 Panasonic LCD/Plasma, 1 Sony LCD, 1 NEC Plasma, 2 Yamaha HTS, 5 Sharp LCDs, 5 Toshiba LCDs, 7 Philips Plasma/LCD, 1 Hitachi Plasma, 10 LG LCD/Plasma, 16 Samsung LED/LCD/Plasma, 1 Thomson Plasma, 1 Atec LCD, 1 Hanspree LCD, 1 Xerox LCD, 1 Harwa LCD, 2 Proview LCD, 2 Hyundai LCD, 1 "Onn" LCD, 1 Grundig LCD, 1 Dell LCD, 1 iiyama LCD, 1 Acer LED, 1 Logik LCD, 1 Baird (China) LCD, 6 Bush LCDs, 19 Vestel LCDs

Last edited by tom66; 01-17-2012 at 05:20 PM..
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Old 01-17-2012, 05:15 PM   #2
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Default Re: A guide to fixing/troubleshooting some common plasma TV problems

List of problems and potential solutions
(I assume you have already disassembled your TV)

The picture is slow to update (motion blur) and has a purple or lilac tinge to it. When first turned on, it may look like a lava lamp that has not yet warmed up. The screen may not be evenly lit - it may look a bit "foggy". Half of the screen may be more distorted than the other half. When running, it may look like this (excuse the camera shake). This is in about 95% of cases the Z-sustain.

There is usually at least one fuse on the Z-sustain. First, unplug the TV and give it 5 minutes to discharge the capacitors. Then, set your DMM to the 200 ohm range. Touch the red and black together. Note the reading, it should be around 0-2 ohms. Now, touch one probe on one end of the fuse, and the other probe on the other end. If your DMM reads "1" on the left hand side, or "OL", the fuse is blown. If you get the same value as when you touched the probes together, the fuse is not blown, and the board is okay.

You should replace the fuse. Should that then blow again, you need to repair or replace the Z-sustain. Diagnosing a particular fault is tricky and requires considerable experience. Unless the Z-sustain is very expensive, or difficult to repair, I would advise a simple swap of the board.

If the fuse shows as okay, open a thread - the problem is more complex.
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Old 01-17-2012, 05:15 PM   #3
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Default Re: A guide to fixing/troubleshooting some common plasma TV problems

The picture has lines going from left to right in fixed positions. The Y-buffer is faulty or the Y-driver connections are loose. In rare cases, it can be the control board. If on dark scenes the lines are lit up with the rest of the screen, then it's most likely a control board problem.

Unplug the TV and give it 5 minutes to discharge. Locate the Y-driver connection responsible for the lines in question. (The position on the Y buffers is approximately the position on the screen.) If you're not sure, disconnect what you think might be the connector that is at fault. If you then get a fat black bar in the middle of the screen and you can't see the lines any more then it is that connector or buffer IC. First, try reseating the connector and using a small amount of contact cleaner, if available. If that fails, it's likely the buffer IC for that group of rows has failed. This means the buffer itself needs replacement. The buffer is often inexpensive and easy to replace.

Last edited by tom66; 01-17-2012 at 05:23 PM..
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Old 01-17-2012, 05:16 PM   #4
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Default Re: A guide to fixing/troubleshooting some common plasma TV problems

No picture. Big one, lots of causes, lots of problems. First, check if you have sound when you plug in a source. If so, it's probably not a power supply fault. Does the set respond to the remote control or side buttons? Is it stuck in standby? There are too many power supply faults here to debug - create a thread.

However, if it doesn't seem like a power supply fault - if you have sound and the TV will respond normally - then it's likely a Y-sustain or Z-sustain fault.

If you don't have sound: First, turn the TV off and unplug it from the wall. Give it 5 minutes to discharge the capacitors. Then, unplug the connector going to the Z-sustain. Now plug it in, do you have sound? If so, the Z-sustain is failed. Now, give it another 5 minutes and then disconnect the Y-sustain and re-connect the Z-sustain. If it now powers up with sound, then the Y-sustain is faulty. With a Y-sustain problem, it can also be a buffer problem. If your TV has two buffers (upper and lower), disconnect the upper buffer (wait 5 minutes before doing so), and see if you get a picture on the lower of the screen, then swap around. The board that when removed gives a picture is faulty. If your TV has only one buffer, remove that and see if it comes on with sound.

If you have sound: This is often a Y-sustain fault. There is usually at least one fuse on the Y-sustain. First, unplug the TV and give it 5 minutes to discharge the capacitors. Then, set your DMM to the 200 ohm range. Touch the red and black together. Note the reading, it should be around 0-2 ohms. Now, touch one probe on one end of the fuse, and the other probe on the other end. If your DMM reads "1" on the left hand side, or "OL", the fuse is blown. If you get the same value as when you touched the probes together, the fuse is not blown.

You should replace the fuse. Should that then blow again, you need to repair or replace the Y-sustain. Diagnosing a particular fault is tricky and requires considerable experience. Unless the Y-sustain is very expensive, or difficult to repair, I would advise a simple swap of the board.

Last edited by tom66; 01-17-2012 at 05:19 PM..
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Old 01-17-2012, 05:17 PM   #5
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Default Re: A guide to fixing/troubleshooting some common plasma TV problems

To be continued.
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Old 01-17-2012, 05:17 PM   #6
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Default Re: A guide to fixing/troubleshooting some common plasma TV problems

stash point #2 for more stuff
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Old 01-18-2012, 01:54 PM   #7
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Default Re: A guide to fixing/troubleshooting some common plasma TV problems

[Oops. Looks like I can't edit after time has expired.]

Picture sparklies on some scenes. If in dark scenes or sometimes even in light scenes a subtle flickering of red, green or blue (or a combination of all three) is visible, then you have the "sparklies" problem. It may look like this, a green mist on the sides of the screen. This affects LG the most, but some Samsung TVs have the problem too. I have never seen a Panasonic with this problem, but I would not rule them out.

Sparklies are the bane of plasma TVs and are caused by numerous problems, including, but not limited to:
  • Power supply voltages
  • Sustain sub-voltages
  • Timing settings
  • Control board firmware
  • Panel aging
The first three can be fixed in 95% of cases. The fourth is more difficult to fix but can be done by some people with the right equipment (reprogramming the firmware.) The fifth is not possible to fix, without replacing the panel, which is too expensive to justify replacement in most cases. Luckily, the fifth is usually correctable and is a result of the first three not being in specification.

Power supply voltages
The power supply voltages are different and unique to each panel, due to manufacturing variations and model specific parameters. They are always indicated on the panel with a sticker like this.

You will need to get out your DMM.

If you have a manual ranging multimeter (with, for example, 200m, 2000m, 20V, 200V, 100V for the DC range) set it to the 1000V DC range (or closest range above 200V, e.g. 500V or 600V.) Some Vs voltages can exceed 200V on some TVs.

If you have an auto-ranging multimeter, set it to DC volts.

Then find the test points on the power supply. In my limited experience the best place to test these voltages is on the output connectors of the power supply, which are usually labelled, with the positive stuck next to one of the pins (jammed in there) and the negative in a spare screw hole in the frame. Here I am probing the Vs voltage on this TV. As can be seen in the image, the voltage measures 187.9V. It should measure 186V. This 1.9V difference can make a substantial difference to the performance of the PDP.

Even if the voltage is less than 1V out, adjust it down to meet the sticker rating as close as you can. (I adjust to within 0.2V.)

The adjustment is usually near the output connectors and is labelled. SLOWLY turn it one way or the other to meet the required output voltage.

Also check Va, which is around 60V. Adjust it in the same way.

Now the voltages are in spec, check the picture. Has it improved? Don't be afraid to say it hasn't - this doesn't fix all sparklies. Sometimes it can improve them slightly, but not completely. If so, on to sustain voltage adjustments.

Sustain sub-voltages
On the Y-sustain, there are sometimes additional voltages. These are generated from the main Vs and Va voltages by one or more voltage converters. They look a bit like these. Samsung PDPs tend to put the converters on the board itself and not on little daughter-boards.

Sometimes there are also converters on the Z-sustain for the Zbias voltage.

You are looking for the potentiometers (indicated by the red arrows) to adjust the voltage settings. You are also looking for the test point for each voltage. You may need to refer to the service manual to find the test points - as they are often in obscure places. The sticker indicates the correct voltages; sometimes they are written in a strange order so you may need to refer to the manual for what each number indicates.

The method of adjustment is the same as for the Vs and Va.

Still not looking great? Sometimes this is caused by timing settings... I will discuss that in another post in this thread shortly.
Attached Images
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File Type: jpg DSCN6905.JPG (145.5 KB, 1633 views)
File Type: jpg DSCN6907.JPG (189.7 KB, 1218 views)
File Type: jpg DSCN6909.JPG (211.8 KB, 1813 views)
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Old 01-20-2012, 01:44 AM   #8
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Default Re: A guide to fixing/troubleshooting some common plasma TV problems

Its a good guide for plasma TV's which might help me one day as I have 50" LG working fine so far, maybe you could write another guide for LCD's
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Old 09-22-2012, 04:57 PM   #9
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Default Re: A guide to fixing/troubleshooting some common plasma TV problems

Tom! This is awesome! You should get this out there a little more, share the link with people looking for information on plasma TVs. Again, GREAT job on this. By the way you have me hooked... do you intend on adding anything else to this? I'm subscribing in the event that you do!
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Old 09-22-2012, 05:03 PM   #10
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Default Re: A guide to fixing/troubleshooting some common plasma TV problems

I've considered using the new 50" Panasonic to show how I diagnose a fault on a plasma. But I've covered most of the main faults with plasma TVs. Power supply faults belong in a more general thread (usually covering both plasma and LCD), but there are -so many- to list.
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Old 09-22-2012, 07:05 PM   #11
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Default Re: A guide to fixing/troubleshooting some common plasma TV problems

I hear you! You did such a good job on this I was ready for more! lol! I don't know if you would be willing to take a picture of the back of the TV and label what components are what. I'm not asking for myself, but for someone who is just starting or has no clue how to ID the components, they can get a better idea of what a z-sus at least looks like or whatever they may be in question of.

I'm just throwing that out as a suggestion. Again, I think you did a GREAT job (big understatement) on this thread. To a novice or beginner this is going to be a big help! Hell, I learned some stuff off of it and I'm going to break out the TVs that I lost it on and go back to check it over again. I have had an issue when it comes down to figuring out what component had failed in the first place other than the fuses being the indicator. Again, thank you for this post, it is an example of what truly sets Badcaps forums apart from the rest, along with members like you! Thanks again!
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Old 09-24-2012, 04:31 AM   #12
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Default Re: A guide to fixing/troubleshooting some common plasma TV problems

Great guide Tom I'm thinking of getting a few broken tellies and giving this repair hobby a go. I know where I screwed up on my Sammy so looking forward to following your advice on to experthood.
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Old 11-16-2012, 11:08 AM   #13
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Default Re: A guide to fixing/troubleshooting some common plasma TV problems

Awesome write up.

Having trouble identifying what most abbreviations are like Va Vs are for and what exactly do the sustain and buffer boards do?
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Old 11-16-2012, 11:14 AM   #14
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Default Re: A guide to fixing/troubleshooting some common plasma TV problems

Nice job Tom. Thanks for putting this together. It should help a lot of people.
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Old 11-16-2012, 11:37 AM   #15
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Default Re: A guide to fixing/troubleshooting some common plasma TV problems

Va/Vda/Vdata = Horizontal Data Voltage. This is used to "write" to the pixels on the display and store the image during the addressing phase. Failure is very rare, but can happen. If it did fail, the panel would likely still glow, but you'd have no picture. Most likely the failure is due to shorted COF chips, on the panel, which writes off the TV.

Vs/Vsus = Sustain Voltage. Main power bus in the TV. Used to make the written pixels glow due to electron excitement, which causes UV emission, which is then converted into visible light using the phosphors. Failure causes no picture. Low voltage causes maldischarge (purplish look, uneven brightness, flickering pixels, etc.)
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Old 11-16-2012, 01:33 PM   #16
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Default Re: A guide to fixing/troubleshooting some common plasma TV problems

This is very good information Tom thank you very much.
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Old 11-16-2012, 02:09 PM   #17
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Default Re: A guide to fixing/troubleshooting some common plasma TV problems

This is just great Tom , now everybody can fix there own TVs, we are obsolete.
Just kidding, You are doing an awesome work here, though I'm skipping on these TVs.
I agree with rigeback, it would be nice to have one for the LCD TVs too, maybe together with monitors.
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Old 11-16-2012, 02:15 PM   #18
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Default Re: A guide to fixing/troubleshooting some common plasma TV problems

If I get the time, I will create an LCD guide, but there are vastly more problems with LCDs than plasmas. Especially as tab bond failures are more common nowadays.
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Old 01-08-2013, 08:16 AM   #19
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Default Re: A guide to fixing/troubleshooting some common plasma TV problems

Hi Tom, this is a really nice thread and so well written!

Do you have any suggestions for a problem I have with my old 42" plasma TV which is an NEC PX-42VP4G/S. The symptoms are thin vertical lines which seem to move occasionally and vary in colour. Other than these lines the display is fine but they are obviously distracting. I took the TV to a local electronic service shop and they say that because the lines are spread the entire width it can't be the Y-Driver but is most likely the chemically bonded connections to the screen itself which can't be fixed and would cost about 1000 to replace the screen. Does your guide referring to horizontal lines apply to vertical lines that I have? As you can tell I'm pretty stubborn with fixing things and like you I hate scrapping this sort of thing unless I am convinced there is no other option. Any advice would be greatly appreciated!
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Old 01-08-2013, 08:33 AM   #20
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Default Re: A guide to fixing/troubleshooting some common plasma TV problems

budm guide is good on lcds and monitors
http://www.fixya.com/support/r509388...shooting_guide
http://www.fixya.com/support/r615007...roubleshooting
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