Plasma 42V7 problem - please help!!!

[tom66]

Re: Plasma 42V7 problem - please help!!!

Great to hear. But, usually when an LG gets sparklies, it means a firmware update is necessary. The panel has aged, new timings need to be loaded onto the microcontroller.

Some people have reported that -increasing- the Vs by 5V can help in this case. Be careful when you do this.

[scokljat]

Re: Plasma 42V7 problem - please help!!!

Great to hear. But, usually when an LG gets sparklies, it means a firmware update is necessary. The panel has aged, new timings need to be loaded onto the microcontroller.

Some people have reported that -increasing- the Vs by 5V can help in this case. Be careful when you do this.

Well Tom I'm affraid you're probably right. I did some testing today, I have some interesting results. I adjusted Vs, Vsc and -Vy plus/minus 5 volts, I didn't make it much better. Acctually it make it worse when decreased Vs for 5 volts. I tweaked VsetUP and VsetDN and couldn't get it 100% ok but it's now as good as it can possibly be in this condition. There are random sparkles all over the screen noticeable mostly on black areas or light to dark transitions. Most of the time picture is vivid and bright, but when it comes to full white picture there is some lack of brightness, screen burns are visible from subtitles and channel logos in the corner as well as bars left and right from usage of 4:3 conversion. When full white screen is displayed IPM's and/or other parts inside produce more buzzing noise which is I suppose normal.

In menus I found "White Wash" option and tried it few times for few minutes. I don't see any difference and acctually I don't see why and how should full white screen "wash" screen burns?! Eh?

I also found and turned on "Eco mode" which decrease brightness little bit while conserves energy. Important thing is that TV still has lot of brightness (acctually for me it's too bright in normal mode), BUT I noticed IPM modules run lot cooler in "Eco mode", especially Y-SUS IPM. I believe it can prolong life of TV a lot.

One thing is peculiar, if there is full white screen, screen burns are visible and there is some lack of brightnes like there is lack of power, BUT, if there is only full white part of the screen, screen burns are not visible and there is no lack of brightness, even on areas with severe burns it's 100% white and uniform.

TV is obviously well used. It looks very clean inside, I suppose it was used in a clean, non smoking place.

Finally, I got automatic test patterns from CTRL board. The CTRL board is capable of generating its own video test patterns. There are two possibilities, both based on jumper positions R406 and R407. Problem is that patterns change every second and I don't know how to stop it or choose which pattern to display. Pressing buttons on TV make no difference, and I don't have remote control. Test signals just confirmed screen burns like with "white wash" and lot of sparkles on full white to full black transitions. There are some patterns with thick full white bar going across screen and no burns were visible.

About the firmware upgrade, I don't know where to find ROM image, and I don't have JIG to program the CTRL board flash. I only can desolder flash IC and try to program it on a PC with proper programmer.

And finally, I believe it could still be a capacitor issue. There are some post about people fix random sparkles with Y-SUS recap. There are several 10u/350V and 150uF/250V Samwha caps near IPM heatsink that get quite hot. It's obvious when TV displays full white image there is lack of power. ..or could it be because I used Sanyo STK IPM and not original LG IPM?!


Guys, what do you think?? Please, I really need some suggestions.


Take look at the pics...
and movie:
http://www.youtube.com/watch?v=soZ9j...ature=youtu.be

This post describes it well:
http://www.electronicspoint.com/re-l...e-t243746.html

Thanks and cheers!

Suad

[tom66]

Re: Plasma 42V7 problem - please help!!!

I think it's fairly normal for the older plasma TVs to struggle with full white, because that means drawing close to 400W, and the power supply is starting to struggle because it is made very cheap. You will sometimes see Vs drop by a couple of volts when on full white.

I had an LG with the same issue as yours and in normal content the sparklies were essentially invisible from a 10 foot distance. It was 720p, so the dots were less visible, but it was still annoying.

[scokljat]

Re: Plasma 42V7 problem - please help!!!

I think it's fairly normal for the older plasma TVs to struggle with full white, because that means drawing close to 400W, and the power supply is starting to struggle because it is made very cheap. You will sometimes see Vs drop by a couple of volts when on full white.

I had an LG with the same issue as yours and in normal content the sparklies were essentially invisible from a 10 foot distance. It was 720p, so the dots were less visible, but it was still annoying.

Well, this set is obviously well used. I'll check some caps when I get ESR meter. Actually, it's watchable even with dots/sparkles and slow white-to-black transitions. I can live with that, but if possible I would like to make it better.

What about the firmware update? Do you think it will solve my problem and TV will get rid of sparkles and visible burns on full white screen?! Service manual says ti should.

Btw, I tested Z-SUS output with oscilloscope. Wave looks ok, but it is around 200V peak-peak?! Service manual says it should be 165V and it's non adjustable. Did I do something wrong oscilloscope settings or readings? See pics.

Cheers!

Suad

[tom66]

Re: Plasma 42V7 problem - please help!!!

Remember your scope and probe probably have a combined 5% error.

The Z sus only drives between Vs and Ground and handles the energy recovery portion of the sustain cycle ("stealing" energy from the panel's integral capacitance, the energy of which would otherwise be dissipated as heat.) So if Vs is around 200V, getting a peak-to-peak of 212V is about right...

[tom66]

Re: Plasma 42V7 problem - please help!!!

PM muskin regarding getting your board reprogrammed if you decide to do it - he has the jig he bought for his TV.

[scokljat]

Re: Plasma 42V7 problem - please help!!!

The Z sus only drives between Vs and Ground and handles the energy recovery portion of the sustain cycle ("stealing" energy from the panel's integral capacitance, the energy of which would otherwise be dissipated as heat.) So if Vs is around 200V, getting a peak-to-peak of 212V is about right...

So what does mean this 165V on this picture of Z waveform form service manual?

I noticed there are to possibilities on 42V7 regarding ZSUS board. One has adjustable trimmer for Vzb and other does not have it and Vzb is non adjustable. I also noticed there are two versions of maldischarge ROM. One is "With VZ" and other is "W/O VZ". I suppose it maybe refer to which ZSUS board is installed and proper CTRL board and/or maldischarge ROM have to be used in conjuction with type of ZSUS board. What do you think, am I right?!? There are also new voltage settings for Vsc and -Vy after maldischarge ROM installation...

Cheers!

Suad

[tom66]

Re: Plasma 42V7 problem - please help!!!

As far as I know, Vzb on the older boards is just for getting the gate drive waveform correct to the IPM's internal MOSFETs; so it shouldn't matter if you can't adjust it, because it is probably automatically set on the newer boards. Strange though, LG would usually release a whole new panel e.g. 42V8 (which I don't think exists) if they were to make a change like that.

I think 165V is a mistake. Also consider that your scope is probably including the ringing on the waveform, try and measure it using the cursors feature.

[scokljat]

Re: Plasma 42V7 problem - please help!!!

I did some testing and "tweaking" of SetUP and SetDN controls on YSUS, this time just looking at the screen, without oscilloscope ;-)

Well, finally I got very nice full white screen. It's white, uniform, without visible screen burns. There is no drop in brightness, PSU bears it very well.

However, there are still sparkles mostly on bright-to-black transitions and there is very noticeable "memory effect" or ghosting when something bright stays for some time and then disappear. Eg. when subtitles disappear, there are subtle sparkles slowly disappear on it's place for a second or two. ..or on credit roll at the end of a movie, black background with scrolling white text, text leaves ghosting trail with some sparkles...

I noticed some caps get very hot on YSUS and ZSUS. One even electrified me little bit when I touched it's top!! I can't wait my ESR meter to arrive so I can test caps.


If I tweak SetUP and SetDN to have less sparkles, then full white screen look little bit worn with visible screen burns.

If I tweak SetUP and SetDN to update faster so there is less ghosting, I get sparkles all over the screen no matter what is displayed.

I wish I have JIG to try firmware updates...


Stay tuned...

Cheers!

Suad

[scokljat]

Re: Plasma 42V7 problem - please help!!!

Look at my Y-SUS output wave. Isn't right part of the wave incomplete?! It doesn't look like on picture from service manual. What do you think?!

Cheers!

Suad

[tom66]

Re: Plasma 42V7 problem - please help!!!

I noticed the same thing on my 42" LG, but I never quite figured it out - maybe the new ROM adds those timings to minimise the sparkling?

[scokljat]

Re: Plasma 42V7 problem - please help!!!

I noticed the same thing on my 42" LG, but I never quite figured it out - maybe the new ROM adds those timings to minimise the sparkling?

Next thing I don't understand is why I need to connect the oscilloscope triggering probe to trigger point VS-DA on the Control board as they say in service manual?? What it is for and how to adjust oscilloscope to use this extra signal? I connected second probe to ext. trig. input of my oscilloscope and I tried several options but can't find any benefit of the triggering probe. Perhaps I'm doing something wrong...

When I measure Y-SUS output wave I connect a probe to B39 test point and then manually adjust all knobs and trigger level to display a clean steady wave.

About the ROM upgrade, I got all ROM files from Barry :-) Now I have to figure out how to flash the EPROM without a JIG. I had in mind to buy new flash chip (cheap) and to put it (or solder) in TSOP 48pin adapter and than program it with standard programer (which I don't have), desolder it out and finally solder new programmed chip on it's place on control board.

Sometnihg like this:

http://retrohacker.info/viewtopic.php?f=13&t=6

http://www.ebay.com/itm/180723399914...=p5197.c0.m619

http://www.ebay.com/itm/120929078072...#ht_2234wt_946

..sounds easy ;-)


Cheers!

Suad

[tom66]

Re: Plasma 42V7 problem - please help!!!

Next thing I don't understand is why I need to connect the oscilloscope triggering probe to trigger point VS-DA on the Control board as they say in service manual?? What it is for and how to adjust oscilloscope to use this extra signal? I connected second probe to ext. trig. input of my oscilloscope and I tried several options but can't find any benefit of the triggering probe. Perhaps I'm doing something wrong...

My guess would be VS-DA is one of the signals going to the IPM. However, if the video signal has large variations in brightness across the screen, it may cause issues with a normal edge trigger - you really need a delay trigger for this. Have you played around with the hold-off control?

About the ROM upgrade, I got all ROM files from Barry :-) Now I have to figure out how to flash the EPROM without a JIG. I had in mind to buy new flash chip (cheap) and to put it (or solder) in TSOP 48pin adapter and than program it with standard programer (which I don't have), desolder it out and finally solder new programmed chip on it's place on control board.

Looks fun. Never done it myself, be careful not to damage the board as it will be very difficult to repair.

[scokljat]

Re: Plasma 42V7 problem - please help!!!

Can't find any of my friends with a decent eprom programmer capable of programming 32mbit 48pin flash chips even if I use TSOP-DIP adapter.

Anyways, I'm testing this TV in "real world" environment for few days. It's switched on few hours a day, I watched few series. Actually, it is quite watchable. I did fine tuning of setup and setdn, sparkles and ghosting are visible if you stare at the screen from 0.5m, but when you relax and watch TV from 3-4m it looks quite good. Colors are good, contrast is great, only thing that sucks is that when picture is near all white it looks little bit worn with visible screen burns.

I'm still waiting for ESR meter to arrive. I'll test saome caps on YSUS and PSU and probably replace some of them anyways.

Cheers!

Suad

[tom66]

Re: Plasma 42V7 problem - please help!!!

Looks quite nice! You have learned a lot about plasmas too. Very good educational experience to take an old plasma display and get it working.

Would you be interested in an original LG remote which should be compatible with this TV? PM me if so - my dad has one left over because the only thing it doesn't do is the digital TV guide feature on LG LCDs so he had to replace it.

[Th3_uN1Qu3]

Re: Plasma 42V7 problem - please help!!!

I have to work on this same plasma today. I have no picture.

It powers on and all voltages on the PSU (Va, Vs, Vcc, 6v, 12v) check out okay. No bad caps (visually at least). Z sus is mildly warm. On the Y sus the only heatsink that gets warm is the one with the two TO-220 transistors, others are cold. All fuses in sight check good. Y sus buzzes, a bit loud for my taste.

I tried disconnecting each board, no change. However, i get some random colored dots and small lines on the display when i unplug either or both buffers from the Y sus.

This is my first plasma repair so i need some pointers here.

[tom66]

Re: Plasma 42V7 problem - please help!!!

Probably best to put this in a separate thread -- his problem was intermittent flickering picture then sparklies whereas yours is no picture. May get confusing otherwise.

You probably have a bad IPM on either SUS and you will need a scope to test the output of each SUS. The voltages compare to panel sticker OK? Check -Vy, Vsc and Vzbias, too.

[Th3_uN1Qu3]

Re: Plasma 42V7 problem - please help!!!

I'm here at a GSM service centre, which just happens to have laptops and TVs brought in, and i like those more, so that's what i picked to work on. We don't have a scope here so i'll bring mine in tomorrow.

Haven't checked Vsc, -Vy, Vzbias, will do so now. 5v and 3.3v are good.

[tom66]

Re: Plasma 42V7 problem - please help!!!

Voltages on sticker separated by five slashes usually

[N/A] / Vsc / -Vy / [N/A] / Vzbias.

The others are for older modules using Vset and Vset2... or for stupidly big 71" 1080p prototypes (gold plated... they made one that was gold plated...)

[tom66]

Re: Plasma 42V7 problem - please help!!!

Panel information
http://www.tgohome.com/ServiceManual...42V7&typekey=0

42V6 may help too
http://www.tgohome.com/ServiceManual...42V6&typekey=0