Vizio VX42L Pop then Screen blurred - LCD Problem

[stauffercaps]

I picked up a Vizio VX42L LCD TV that was not working for nothing. It would work fine for a few minutes then you would hear a POP and the picture would get all blurred. Once this happens the TV power buttons on the side would not respond nor would any of the input, volume, or channel buttons. Removing the power cord is the only way to get it back to normal function. It will only work for less than a minute before popping again.

I removed the back cover to check the power supply and invertor boards for visible defective caps but did not find any that visually looked bad. When the tv was laying face down on the kitchen table the TV worked fine all day but as soon as the cover was put back on and standing upright it would pop again. This made me think it might be heat related? I uploaded a YouTube video of the pop and screen display when it messes up.

Vizio Pop Problem:
http://www.youtube.com/watch?v=wXZ_lt0vmpA

Thanks in advance for any troubleshooting tips or suggestions.

Adam

[Th3_uN1Qu3]

Looks like a logic board issue, however that pop sounds like arcing in the inverter or CCFLs... when that happens it's like a small scale EMP, it could easily have enough energy to confuse the hell out of the logic board, hence the artifacts you're seeing.

[stauffercaps]

I uploaded some images of the components.

[retiredcaps]

Originally Posted by stauffercaps

I removed the back cover to check the power supply and invertor boards for visible defective caps but did not find any that visually looked bad.

There are a number of caps "hidden" underneath the heatsinks/shields. If you search this forum for "VX42L" you will see 2 other posters who found bad caps hidden away.

[stauffercaps]

Thanks for the responses. I did read the other posts that had bad caps on the slave and master invertor boards and the C241 Cap that was bulging on one members power supply. None of my caps appear to look defective on any of the boards, which from what I have read in this forum doesn't really mean that they are good since they do not look leaky or bulging.

Would you recommend replacing all the caps? Should I start one board at a time? Is a cap what is most likely to be making the "popping" sound?

Thanks again for the advice.

[shovenose]

Well caps can pop only once

[stauffercaps]

I guess I will proceed with replacing the Master and Slave Inverter Caps just to try something since another poster had bad caps on these boards.

Ordered 4 replacement caps from DigiKey on Monday and got them yesterday just 4 days from ordering to my door is pretty quick.

Uploaded a pic of the Master Inverter board to show the caps I plan on swapping. More to come. Thanks for the direction from those that have replied so far.

[Quasar]

Pop sound is high voltage arc. Look for pinched wires, loose or bad connector (burn marks?), blackened marks on or across PCB traces, blackened spots on metal near any connections from inverter to CCFL's including at the tube ends. Look for dust in and around HV connections. Has this occurred with a change in humidity levels (rainy day).?

May have to pull panel apart to get to all of those spots.

When the tv was laying face down on the kitchen table the TV worked fine all day but as soon as the cover was put back on and standing upright it would pop again.

Look for what might be happening when you put the cover on that could cause it. Stand unit up while cover is off and see if it happens. Or, lay it down with cover on and see if it pops.

Going right to cap replacement is just fishing for an answer. It doesn't make sense.

[retiredcaps]

Originally Posted by stauffercaps

I guess I will proceed with replacing the Master and Slave Inverter Caps just to try something since another poster had bad caps on these boards.

I agree with post #2 and post #8 regarding the arcing for the popping sound. I only suggested looking underneath the heat shields for bad caps if you didn't see them in your initial inspection.

[stauffercaps]

Quasar and retiredcaps-

Thanks for the helpful suggestions, I will do a deeper inspection hopefully tonight and see what I can find. I will update you on my findings.

[retiredcaps]

Originally Posted by stauffercaps

Quasar and retiredcaps-

Thanks for the helpful suggestions, I will do a deeper inspection hopefully tonight and see what I can find. I will update you on my findings.

If you do this test in a very dark room with the back cover off, it might be easier to find out where the popping is.

If you have safety glasses, this would be good time to use them.

[Quasar]

Checkout this thread last post today

http://www.badcaps.net/forum/showthread.php?t=10816

Could be burnt inside a connector that looks fine from outside.

[stauffercaps]

Before tearing down the TV again I recreated the problem standing upright which it did. I layed it facedown on the table to tear apart and tested again. The problem repeated two times so I thought lets tear down.

Sadly once I got everything torn apart I could not get the TV to mess up. Urgghh. So I thought maybe it when the back cover was on it trapped more heat inside causing a fault to occur. Couldn't get it to mess up. BUMMER! Next i thought maybe it would mess up in the upright position so I leaned the tv with the back cover off against the kitchen wall. Talk about frustrating!

I did look at the Power Board, Both Invertors, and LCD controller carefully and did not smell any burnt smells nor did I notice any outright burn marks, etc. I visually un hooked the cables and connectors non of which looked burnt like that other post Quasar suggested, although that Corona Effect was very interesting.

Couple Questions:
Do I need to tear the TV down to the LCD level to see the CCFLs?

Are there two CCFLs, one on each side? One inverter board for each CCFL?

The LCD Controller at the top had two hard flat ribbon cables that go to a PCB on the top of the TV which is hidden under the black bezel. Any idea what these are?

Disappointed but I'm not giving up despite suggestions from the wife to get that TV off the kitchen table!

[Quasar]

Have you replaced the caps on the inverters yet?

Time to move on to the power supply. Yes, heat might be the issue, and is typical of these sets in general, but failed caps could be too. If you have no way of checking the ESR of the caps, then "shotgunning" (replace them all) may be your only choice. You might spend ~$20 for them total.

I think one of the other VX42L threads list them too.

[Quasar]

Also, keep an eye out for threads with the RCA L42WD22 like this one:

http://www.badcaps.net/forum/showthread.php?t=11240

It uses the same 2 inverters as yours. One MASTER one SLAVE joined by the wider of the 2 blue ended ribbon cables. Never know what info you might discover.

[stauffercaps]

Originally Posted by Quasar

Have you replaced the caps on the inverters yet?

I have not replaced any caps but did purchase the four caps from digi-key for the inverter boards. I have no way to test caps either so I guess I might be ordering a bunch of replacement caps and blasting these PCB's with some caps.

Good catch on the other thread going for the RCA with no picture. It has the same inverters and LCD controller as my Vizio does.

I cant say thanks enough for all the suggestions...

[crtfool]

Is any part of the inside of the back cover metal? If it is, maybe you should cover all the exposed metal with something to completely insulate it before reattaching it. Also, install a minimum number of screws to secure it safely - maybe 4, 1 in each corner - and then operate the TV in the upright position to see if it still fails.

Also, another thought - I just looked at the pictures that you posted - it may be possible that one of the boards attached to the metal frame might be flexing enough for the bottom of the board to touch the metal underneath it when the back cover is closed and completely secured. Try slipping something like a thin sheet of plastic, rubber, or even cardboard under each board to act as an insulator to prevent any possible arcing.

By the way - You are a BRAVE man to ignore your wife's "SUGGESTIONS"!

[Quasar]

Originally Posted by stauffercaps

I have not replaced any caps but did purchase the four caps from digi-key for the inverter boards. I have no way to test caps either so I guess I might be ordering a bunch of replacement caps and blasting these PCB's with some caps.

I would get those inverter caps done. From the other post, they seem to be a problem, even if they don't look like they are bad.

Do them and try it. If it works, then you've solved the problem. Then you can do the power supply as insurance against future problems.

[stauffercaps]

Ok, I got the 4 caps on the inverter boards replaced. The replacements are a little longer than the originals so they don't fit in the cutouts on the PCB as well. I hope it will be alright. I have the tv all assembled and running so we will see how long it will run without messing up.

Again, sorry about the quality of the pictures (iphone) but you can get the idea.

Also, I hear a slight "buzzing" or "humming" from the power supply board. Is that normal? You can't really hear it unless you get close to it and even less with the back cover on. I was just wondering. Thanks.

[Agent24]

I have a recapped LCD which makes a buzzing noise, though the original owner doesn't know as it was used in a noisy office, and it's a quiet noise anyway.

However on Newegg that exact same monitor has several reviews stating that some people get a buzzing noise when the brightness control is set to anything other than 100%.

I found that if I turn my brightness onto 100% the noise greatly diminishes. Probably just someone didn't apply enough glue to something in the factory. So I guess from that at least that my monitor is "normal" to make that noise (in some cases)


But that is just my theory, probably better to see what someone else has to say about it !!