Panasonic 50" VT20 arcing at edge of panel to frame

[tw2005]

Re: Panasonic 50" VT20 arcing at edge of panel to frame

Well I have to say I dont live anywhere near the sea or salt that I know of. The TV was not that dusty either.

I understand the idea of insulating the metal bezel of the TV. However before I try that idea out I have a couple of questions.

Why is this metal in the first place? Secondly the metal has a pad on it that rest against the glass. I guess this is to make sure the metal doesnt directly touch/scratch the glass. This pad is conductive. I've used a meter to check and its a fairly low resistance from it to the frame. Why is this conductive if its not meant to discharge the panel in some way? Also wouldnt the electricity thats arcing just flow through this pad? Why the arcing in the first place if this is in contact with the glass/screen nearby where its arcing?

Second question is if I insulate the metal and/or remove that pad where would the charge that builds up go? Would it cause damage to anything else possibly or arc to me if I put my finger near the glass (or rather my kids to be exact) ?

I might try out the idea mentioned about trying to measure the voltage of the spark. Even if it doesnt help anything the idea seems interesting

Does anyone know the voltages I'm meant to measure the test points on the power supply /other boards to see if its perhaps over voltage or something like that?

I just lifted the front bezel away from this V20 for a look. There is nothing conductive under that. Just a plastic frame with an aluminium fascia. Under there is thin non conductive tape.

Along that edge where you see arcing is a metal strip, under the metal strip against the glass is EMI shield tape / foam. Yes it is conductive and meant to be.



Now I'm just wondering if it's static discharge and that tape has broken down because if the tape is conductive and it's stuck to the metal plate why would it jump and discharge at a point further away?

Just throwing that one out there.

also be aware as you pull bits away from the frame or panel it may loose rigidity , flex and crack the panel.

Maybe keep an eye out for a 2011 model with a busted SC board and fix it. Probably easier to do that than to work out this one.

[budwich]

Re: Panasonic 50" VT20 arcing at edge of panel to frame

you are not trying to measure the voltage of the spark. you are trying to check / measure any voltage difference appearing at the panel frame (not the bezel... which is removed for testing) to ground. There should be no sparking at this point according to your previous statements which said that once your remove the bezel, the "arcing" stops. Once you know 1... if there is any voltage potential there and 2... if its AC or DC based, you then might be able to determine the source / reason.

[maxvalutech]

Re: Panasonic 50" VT20 arcing at edge of panel to frame

Referring to post #35 by flocko worth looking at your earthing rod for house. Usually near/under meter box check green wire good connection and give area a good soaking. In one house we rented wife was getting small shocks from washing machine and poor earth was cause.

[infrag]

Re: Panasonic 50" VT20 arcing at edge of panel to frame

Measured voltage between the glass and the metal frame of the TV with part of the metal frame off. Theres 26V AC there which stays pretty stable. There is DC there too but most of the time low voltage e.g 3-8volts. However it does spike higher but the auto-ranging meter cant keep up with the jumps so I dont know how high it gets. I'll try later this evening to get more info with the other part of the metal removed and see how high the voltages go with it off.

[infrag]

Re: Panasonic 50" VT20 arcing at edge of panel to frame

I can check the earth spear. Pretty sure the area is wet enough though as I've had the sprinklers on nearby.

[infrag]

Re: Panasonic 50" VT20 arcing at edge of panel to frame

Should I just try and replace the emi tape ? If so any suggestions on where to get it from or should I just try ebay?

[flocko]

Re: Panasonic 50" VT20 arcing at edge of panel to frame

I am more at a loss now with you saying you have 26v AC between PDP glass and frame. Have you measured the the AC mains neutral to earth this should show Ov, as the neutral should be tied to earth and your line voltage should read the same between live and earth and live and neutral.I have found that TV faults can be related to the last thing that was watched , farty sounds coming from the speakers after viewing Blazing saddles, you have not been watching Ghost busters and the PDP has something or someone trapped inside. I am of course joking but do try the mains test

[infrag]

Re: Panasonic 50" VT20 arcing at edge of panel to frame

OK I've taken a few pictures to show the 'solder blob' things. Please give your analysis on this thanks

[infrag]

Re: Panasonic 50" VT20 arcing at edge of panel to frame

Also I've remeasured the voltage on the front of the panel to the frame. From the silver kind of layer (just off from the black part of the glass) to ground there is ~ 34V AC and ~ 3-8V DC.

The symptom I described earlier in the thread has now also returned. I'm not sure if this is a result of me taking the shielding off but the once the TV has been on I turn it off but it stays in 'hot standby mode. It never switches the relay off and goes properly to sleep. USB devices that are plugged in remain powered on. (Ive tried with them removed and it makes no difference.)

[infrag]

Re: Panasonic 50" VT20 arcing at edge of panel to frame

I've also taken a short video with just the bottom metal shield on. It looks a bit crappy because it needs to be dark to see the sparks. I've also used a screwdriver to apply a real little bit of pressure which makes it arc heaps.

https://drive.google.com/file/d/0B-d...ew?usp=sharing

Also after adding this bottom metal bar my TV entered standby again properly. Might be because it was unplugged for a bit while I checked my earth and neutral potential.

The check between the earth pin and the neutral showed up less than 1v.

[infrag]

Re: Panasonic 50" VT20 arcing at edge of panel to frame

I dont know if this helps anyone explain anything but I thought it may hold relevant information. Sorry if you already knew about it... Also I realise its information from a patent which probably isnt the best idea.

https://www.google.com/patents/US20110133640

[budwich]

Re: Panasonic 50" VT20 arcing at edge of panel to frame

i don't actually know how a panel works, especially with respects to "filtering". Your link shows some info assuming the patent or some form is implemented. It appears that is like crt displays where one could cause a slight "discharge" by running your hand across a screen if it was on and even after shut down.

Your measurements are interesting. I am not actaully sure of where / what you are measuring from your word description... maybe a picture showing the measuring setup would clear that up. Further, in your pictures (the two showing the brown / orange tab cables with the little "dot" on what appears to be some form of "rivet"... if I am seeing correctly. Have you measured the resistance (tv off / unplugged) from the "dot" to ground?
Ultimately, I wouldn't expect 30 something ac to arc but the "spike dc" might be an issue... depending on the value. To me, this means that some form of capacitor which would normally filter out /block dc is failing some where.... assuming that dc is normal but not the spike.

[budwich]

Re: Panasonic 50" VT20 arcing at edge of panel to frame

it appears that possibly you have an over voltage condition on one of your boards such that it is imparting sufficient induced voltages on the upper mask. You might have to check some of the voltages generated on the x / y boards to see if anything is strange.
have you checked any video test patterns closely to see if there are display issues that may be hidden by "random video" watching?

[infrag]

Re: Panasonic 50" VT20 arcing at edge of panel to frame

any chance anyone knows what the voltages should be on those boards? Its easy enough to test but I dont have anything to compare it to. If it wasnt working then I'd see power wasnt going somewhere..

[infrag]

Re: Panasonic 50" VT20 arcing at edge of panel to frame

There is 15V I believe thats meant to go to the A board.
It start off at about 14.7-8 volts in Standby mode but goes up to 16V while on. Not sure if that is normal. The other 5V and 3.2/3.2/3.0 voltages all seem normal.

I've checked some voltages at the screws on the Vsus board that are marked high voltage. They have a minus 120-180V on them which scales depending on brightness of the screen. Stable and I dont see any issues there.

The vsus test pins show stable voltages 100-200ish volts DC.

On the Buffer boards there is stable 60V.

I've checked the voltage on the front of the screen again. When arcing the AC voltage does actually jump around but goes UP not down. The low level DC voltage i measured is actually a minus DC voltage or polarity reversed. Not sure if that helps.

[infrag]

Re: Panasonic 50" VT20 arcing at edge of panel to frame

i don't actually know how a panel works, especially with respects to "filtering". Your link shows some info assuming the patent or some form is implemented. It appears that is like crt displays where one could cause a slight "discharge" by running your hand across a screen if it was on and even after shut down.

Your measurements are interesting. I am not actaully sure of where / what you are measuring from your word description... maybe a picture showing the measuring setup would clear that up. Further, in your pictures (the two showing the brown / orange tab cables with the little "dot" on what appears to be some form of "rivet"... if I am seeing correctly. Have you measured the resistance (tv off / unplugged) from the "dot" to ground?
Ultimately, I wouldn't expect 30 something ac to arc but the "spike dc" might be an issue... depending on the value. To me, this means that some form of capacitor which would normally filter out /block dc is failing some where.... assuming that dc is normal but not the spike.

I cant measure to the dots or blobs or rivets as they are either encased in the glass or under the outside layer of the ribbon. I guess the ribbon I could take the outside off it but that kind of feels like danger territory for me. (as in dangerous to damage the TV)

[tw2005]

Re: Panasonic 50" VT20 arcing at edge of panel to frame

There is 15V I believe thats meant to go to the A board.
It start off at about 14.7-8 volts in Standby mode but goes up to 16V while on. Not sure if that is normal. The other 5V and 3.2/3.2/3.0 voltages all seem normal.

I've checked some voltages at the screws on the Vsus board that are marked high voltage. They have a minus 120-180V on them which scales depending on brightness of the screen. Stable and I dont see any issues there.

The vsus test pins show stable voltages 100-200ish volts DC.

On the Buffer boards there is stable 60V.

I've checked the voltage on the front of the screen again. When arcing the AC voltage does actually jump around but goes UP not down. The low level DC voltage i measured is actually a minus DC voltage or polarity reversed. Not sure if that helps.

Vsus should be pretty steady high 190 to low 200Vdc

[infrag]

Re: Panasonic 50" VT20 arcing at edge of panel to frame

Vsus should be pretty steady high 190 to low 200Vdc

OK sorry about that.
I remeasured and VSUS is stable at 208.7

[infrag]

Re: Panasonic 50" VT20 arcing at edge of panel to frame

So then there is the VDA voltage that from what I've read is fine at 60V?
Then the other voltage like i mentioned before that should be 15V starts off at 15.3 and goes up to 16V DC when its on.

[infrag]

Re: Panasonic 50" VT20 arcing at edge of panel to frame

Does anyone know where the ~ 30V AC gets produced that I find on the strip on the front of the TV?