LG 60PX950 ~ Vertical Pixelation Issue

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

Sorry for the extra detail. There was a audible buzzing/pitched tone coming from both the YSUS and the ZSUS before I took the YSUS board off and the set was powered up.

But, no sound was audible as I was working on the board once it was off.

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

Is there a specific way I should be touching the triangular leads on the back in order to either produce a continuous beep (i.e. ... produce evidence of a short), or to produce this buzzing sound you are referring to?

When I got the readings in the pic above, I had the black probe on the top of each triangle, and the red probe on the lower-right hand corner of each.

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

Some new information, but I need some help in this testing process.

I tested under the smaller of the two thermal pads (see image), and got similar results to before (in the 366-368 range with my DMM set on Diode/Continuity mode).

I am getting a continuous beeping when I touch the two particular leads under the heatsinks (see where the two red arrows point), but this is happening only on each of the triangular leads that I've indicated in the black circles. There are ten of them (so, picture 20 red arrows instead of just the two I placed into the image mark-up), and they are obviously in a pattern that indicates that they should be beeping.

Can someone walk me through how to test these properly to look for shorts as related to the heatsink-related leads? I am apparently not doing it in the proper manner.

[Hamie]

Re: LG 60PX950 ~ Vertical Pixelation Issue

They are probably tied together.

I'd say that if none are testing short then youd need to go through the top half of the board and see if you can find something.

With no schematic it would be tough narrowing down your fault.

The best option may be replacing the board, and using a working board to troubleshoot your faulty one.

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

Resistor Testing on YSUS results:

So, I was trying to find patterns and pattern anomalies, and I think I may have found one as I was testing the board's resistors. All of the information below was tested at the 200 Ohm setting on my DMM.

As you can see in the picture below, I found six resistors that all had the same markings (red band, red band, gold band, gold band).

The first three I tested, marked in yellow in the image, all had the same reading of 2.5. The next two I tested (marked in blue) had a lower reading of 1.3. I thought that odd, but the most pressing problem may lie in the fact that the resistor I tested up near the VSC and VY resistors (this one I marked in red), had NO READING at all.

Could this resistor be defective, then, and could it be responsible for the far too low voltage readings on the VSC that I documented in the earlier posts?

I tested this same problematic resistor at other Ohm level settings and only got a reading when I set it at 2,000K. There, it slowly climbed and then it topped out when I had the probes one way, then I reversed the probes and it stopped at 868. Again, odd. But I think the more informative fact is that I got no reading at all on 200 Ohms whereas the other five all easily produced and then reproduced the same readings of 2.5 and 1.3 you see in the image below each and every time I tested them.

Any insights would be appreciated. Trying to track down a logical starting point for repairing this board.

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

Just saw your latest post, Hamie. Thank you.

I think I ended up doing exactly what you had suggested, meaning going through the board and looking for anomalies/issues. Do you think I'm on the right track with this seemingly problematic resistor that sits so close (right underneath) the VSC resistor?

Also, when I tested the VSC resistor itself along with the VY, I expected to get the same results .... because they have identical markings. However, that too was a strange result because the VSC tested at 59.7 and the VY topped out at 43.4. I had to go to 200K Ohms (as opposed to the 200 only you read about in the previous post) when testing the VSC and VY because they gave no reading at all when set at 200 or 2000 or even 20K.

Shouldn't they have given me the same reading, since they are both marked with a gold, blue, yellow, gold pattern?

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

Been teaching myself about these resistor color codes, and it seems like all of the Red, Red, Gold, Gold resistors on this board should be testing at about 2.2 (and anything between 2.1 and 2.3 would be acceptable).

Red = 2 (first digit)
Red = 2 (second digit)
Gold = Multiplier is 0.1

and the last Gold is +/- 5%

so ..... this is 22 x 0.1 which equals 2.2, and therefore anything around 2.1 to 2.3 reading is in the correct range. On the three I marked in yellow back up in post #45, the ones I had said were 2.5, they are actually 2.3 and therefore reading properly. When I held the probes on for about a minute, it dropped from 2.5 to 2.3.

The other two, marked in blue, originally read 1.3 but dropped to 1.2 when I held the probes on for that same minute length. These seem too low, being only about 1/2 of the correct reading.

But, as I mentioned before, the real problem seems to lie in the Red, Red, Gold, Gold resistor up on the top half of the board, and just under the VSC and VY resistors themselves, that continues to give NO READING at all @ 200 Ohms no matter how long I hold the probes onto it. From everything I can tell, this one should be giving a reading in that same 2.1 t0 2.3 range.

Does it make sense to start the repair operation by replacing that particular resistor with either a new one I order online or with a working replacement taken from another board that I may have lying around from a different television?

[dick_barton]

Re: LG 60PX950 ~ Vertical Pixelation Issue

Remove it from circuit and measure it again and replace it if still reading open circuit.

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

Will do.

Thanks.

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

UPDATE:

Advice needed for this YSUS board.

I took the 2.2 Ohm resistor that appeared to be problematic (see Image #1 below) out of the circuit board, as dick_barton had advised. It must be shot, as I am getting no reading whatsoever no matter how high or low the Ohm setting on the DMM. Will order and replace that one.

I have a couple of other questions, though, as I'd like to place all orders simultaneously. I am confused about the readings I am getting on other resistors and on one of the fets under a heatsink as well. Will document along with the pictures below.

-----------

1) There are 5 other 2.2 Ohm resistors (Red, Red, Gold, Gold) on this board. I am getting 2.3 on three of them, but only 1.2 on the other two. Does this mean the other two need to be replaced? It seems unlikely, because I found two more exactly the same (Red, Red, Gold, Gold) on the ZSUS board on the opposite side of the set and those also tested at 1.2. Is that really odd, or commonplace?

It would make sense if the rings were colored (Brown, Red, Gold, Gold) for the 1.2's, but I examined them very closely many times under magnification and they are rather clearly all (Red, Red, Gold, Gold); therefore, I thought, they should all be reading 2.1 to 2.3 range. Any insights here would be helpful. Perhaps it's normal for some of them to read lower in circuit but without the voltage applied, maybe? For, I did not measure them with for resistance a couple of days ago with any voltages applied.


2) I am also concerned about the viability of the VSC resistor and the VY resistor. The VSC (Brown, Black, Yellow, Gold) should be reading, I believe, @ 100K. I only get a reading of 59.7 (should be between 95 and 105 with the +/- 5% tolerance), no matter if the black probe is on the top or bottom.

The VY is an even stranger story. It too is (Brown, Black, Yellow, Gold), and so should also read right around 100K. It reads only 43.4 when the black probe is placed on top, and only 27.2 when the probes are reversed. I found another (Brown, Black, Yellow, Gold) on the bottom half of the board, and that one does indeed read 100.3K. Furthermore, it's odd because when I tested the VY for voltage a few days ago to start this process, it read correctly off the resistor at -VY equaling -179.5 (should be -180, according to the sticker on the back panel). So, almost exactly a match.

Do these need to be replaced as well? Or, given the fact that the VY is passing correct voltage should I just leave that one (or both resistors, VY and VSC) alone?


3) Finally, I think one of the fets under a heatsink might be defective, but it's hard to say. I added a picture (Image #4 below) of the affected area. When touching the black probe to the bottom-left of the triangle, and the red to the bottom right, I get a reading of about 1800 on every other triangular set of leads that has a circle around the bottom left lead. But, on this one fet in particular (inside the star in the image below), and only this one, there is no reading with that same configuration of the probes.

Does that mean it needs to be replaced, or is that a normal result given the configuration pathway of the circuitry itself as show in Image #4 below?


Thanks for reading all of this. I know it's a lot, but maybe I can solve everything at once with help from all of you.

[dick_barton]

Re: LG 60PX950 ~ Vertical Pixelation Issue

When reading resistor values in circuit you must ensure the probes have a good connection with the resistor. The resistor legs can be oxidized. The reading can also be affected by other components around them for example transformer windings / diodes or even if it's across capacitors.

When testing low value resistors remember to subtract any reading obtained when shorting the meter probes together and remove that value from the resistor value read.

So if a resistor does not match the value it should be then it is best to lift one end to make the measurement.

Mosfets generally when faulty go short circuit.

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

Thank you. That's helpful information for me to know and to understand.

So, I think I'm going to assume that the mosfet is okay. And, since all of the "undervalued" resistors have the exact same reading (1.2 Ohms), I'll lift one end on those and test again with the working assumption that they are all okay as well.

Do you think, then, that this single resistor that showed no reading at all (see Images #1 + #2 below) could be responsible for the mass green, sparkling pixelation I always see upon startup of the set? When I try to access the tv's menu by using the remote control, this green pixelation covers almost the entire screen (as a reflection of how much screen the menu itself normally occupies). You can see something similar in Image #3 below where I popped in a DVD. Same type of mass failure.

Apparently, this clear failure to initialize the screen is rooted in the lack of voltage passing through the YSUS, as evidenced and read by only 17V (as opposed to what should be 150V) measurable across the VSC resistor.

So, wondering if it makes sense to you that this one, singular resistor sitting only about 1 cm away and underneath the VSC resistor could be the lone culprit for a screen initialization failure that is so widespread?

[dick_barton]

Re: LG 60PX950 ~ Vertical Pixelation Issue

Unfortunately my working knowledge of plasma's is very little but I would think it worth your while waiting until you have replaced the resistor and then see how the set is running.

If the resistor is open circuit then it would have an effect on the operation of the set (definitely not put in to increase component count or cost) but to what extent without a service manual to study is uncertain.

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

Thanks d_b ~

Going to pick up some of those 2.2 Ohm resistors today up in San Jose. And get a few of the 100K's that govern the VSC and VY resistance as well just in case.

Will start with the 2.2 only, as you advised, and see what happens. I'll post again with the results. Thanks, everybody, for your help so far.

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

UPDATE:

Some good news, and some bad.

Replaced the problematic 2.2 Ohm resistor that sits underneath the VSC and VY resistors. I have only replaced this one so far.

Good news is the green pixelation upon startup is gone. Bad news is there is now nothing but a black screen.

Here are the details:

1) After the board fix and the new resistor in place, with the boards still off the tv, the new resistor read 2.3. Near perfect.

2) The VSC resistor still read 59.7 ohms (DMM probes placed on either lead) and the -VY still read 43.4 ohms (and 27.2 with the probes reversed). So, no change on either one before the board went back on the tv. All looked relatively good. Still wondering if both of these should be reading 100, though, or maybe they are meant to add up to 100? 59 + 43 = 102, so .... very close. Is that possible?

Then, I put the board back on, exactly as it had come off, except that I purposefully didn't hook up the buffer boards yet. Didn't want risk them immediately.

3) Green pixelation was still there at this point. However, I was now getting the full 150 Volts on the VSC reading!!!, and still the -179 on the -VY. So those two voltage readings were great!

I figured I had to hook up the buffer boards at this point to see if doing so would allow the voltage to flow properly through the whole system. When I did, the green pixels were gone, which was and is great, but there was nothing but a black screen upon startup. Completely black across the whole screen, up and down and left to right. There was a momentary flash of white, but it only lasts a fraction of a second (the same as was happening before when the green pixels would follow).

No remote control buttons (Menu, Input, Energy Saver, etc .....) had any effect whatsoever on the black screen. Nothing got fried or started smoking, so I ran it for several minutes this way. Next, I hooked up the DirecTV satellite box to HDMI #1. Still black screen. Hooked up a DVD player next, still black screen. Tried the other 3 HDMI ports. No luck. No menus or anything, and no recognition of the new component inputs which, I read in the owner's manual, this tv is supposed to do automatically.

4) Went to take readings again, with the set still running, and now the VSC Ohm reading was non-existent (just reading either 1 or -1, depending on the probe placements), and so was the -VY (again, just 1 or -1 as far as Ohms go). The new resistor, the 2.2 Ohm, was fluctuating wildly and would not settle on any particular value, though tried to keep returning to 6.8 Ohms.

At that point, I shut it all down, waited a few minutes, and took these same Ohm readings again. With the set powered completely down, the results were:

VSC = 35.5 now, whereas before it had always been reading 59.7

-VY = 43.4 and 27, so virtually the exact same readings as before

and

the new 2.2 Ohm resistor was reading properly once again, meaning 2.3 (just the same as immediately after I soldered it in).

So, the Ohm readings (i.e., resistance) now with the set running are essentially gone when measured on the VSC and -VY, but they are there, albeit seemingly incorrect on the VSC and -VY) when the set is powered down.

The Voltage readings were as follows, with the set running:


VSC = fluctuating wildly between 15V and 35V (was a stable 17V a few days ago, but it should be at 150)
-VY - also fluctuating wildly between 15V and 42V (this used to be stable at -179, with the proper value at -180)

That might help to explain the black screen, but leaves me wondering if:

A) The buffers killed the voltages and disallowed the VSC and -VY resistors to work (which kind of makes sense, except for the fact that the VSC resistance reading was continually and repeatedly coming up as 59.7 Ohms with the set running a few days ago, when hooked up to these same buffers ~~~ only now is it reading 1 or -1 Ohms)

or

B) If only the VSC resistor needs to be replaced (because it has never given me a reading of near 100K), and now appears even more compromised than before ~~~ reading only 35 Ohms when the set is off as opposed to the "traditional" 59.7 Ohms

or

C) Are these far to low and far too wildly fluctuating voltages a result of a faulty capacitor or capacitors? Again, seems kind of unlikely because none of this was happening in such a wild manner two days ago when I was running the same tests


Does anyone have any ideas as to why all of the above would be happening, and the source/origin reason as to why the voltages are so askew now and there is only a black screen with no picture functionality?

Note: I measured the voltages coming into the YSUS board from the PSU at the connector, and they are still perfectly fine. Meaning, Vs still equals 202 and Va still reads 59.


What's the next logical step to take?

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

UPDATE to the UPDATE

Great News!

Got up this morning and decided to disconnect the Y=Buffers one at a time. The result was that the lower buffer is the only thing that now seems compromised (see the 5 images below). The top half of the picture is now seemingly flawless. I ran it for several minutes with only the Top Y-Buffer connected and was able to see NO green sparkling and NO artifacts of any kind on the top half.

Took a short video and posted it on YouTube, showing the same. Here's the link:

https://youtu.be/ycYKw0a9YJo

Bottom half, as you can see, now displays a more traditional "horizontal, green and black pattern", that stretches from left to right all the way across the entire screen, indicating the Lower Y-Buffer is defective.

My question is, has anyone had experience in testing / troubleshooting a singular Y-buffer board (particularly for an LG plasma)? I just want to make sure I can't easily fix this lower Y-Buffer with some approach or a tweak I might be overlooking before shelling out $40 or $50 for a new Y-Buffer board.

Other info:

• All voltages on the VSC and -VY look great, as one would suspect with the Upper Y-Board now functioning and the upper half of the set's picture now flawless.

• The error code (green, blinking LED on the Logic Board) is now reading ...
  
  • LONG, SHORT, LONG, SHORT and then a 3 second pause and repeats
  • (LONG is about 1 second, and the SHORT is a fraction of a second)
    
  • That's a new and different code from anything I saw happening before. I assume it is correlated with the lower Y-Buffer (only).

[freakaftr8]

Re: LG 60PX950 ~ Vertical Pixelation Issue

There you go. Order a lower y buffer. It's shorted and severely dragging down the scan voltages. Most likely why the 2.2 ohm resistor took the brunt of the load.

Most likely one or more scan IC' shorted and if you do not have the equipment to remove 100 pin icees it would be cheaper in the long run to replace that board. Can you snap a picture of the lower scan board. Possibly a diode or something has shorted on that board and it could be an easy repair but highly unlikely. Most likely scan drivers shorted which would render replacing the board other than repairing

[freakaftr8]

Re: LG 60PX950 ~ Vertical Pixelation Issue

Hold on a second was that lower board completely removed when you had half a picture with the green sparkly lines on the bottom side?

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

The lower scan board was not completely removed when I was getting the top half of the picture to come through. It was only disconnected from the YSUS Main Board, while the upper scan board remained connected.

[kca]

Re: LG 60PX950 ~ Vertical Pixelation Issue

Here are some pics for you to analyze. Let me know if they are not large enough or need to be taken from a different angle. All the pics are labeled.