LG 60PA5500-UG Plasma, No Picture

[mouuse25]

Hello everybody, I really need this TV fixed. Any and all help is greatly appreciated

-I tried using the search engine but no one else's problems seem to line up with mine

-I know my screen is good because I have seen the LG logo come up since the issues started

-If I leave the set unplugged for days the sounds works for a little bit, just no image

-I replaced the Y-sus board, and logic control board (because is was cheap)

-checked the Va: 55, Vs:205, VZB: 120 and the main is 5 volt

-disconnected the upper and lower Y- buffer boards, the upper does nothing and when I disconnect the lower I got some funky lines and now I cant get them to show again for a picture

-I want to check the Vy, and Vsc but I can't find clear directions on how to set them or check them I assume I need to solder a resistor/inductor to check this maybe?, (when I set my multimeter to dcv 1000 and set the probes on the board at the assumed location it just gives me scattered readings. I tried both chassis ground and spot marked (-), I posted pictures of assumed location for visual referencing they are the bottom 2 pictures)

-On the logic control board there is a green light that blinks but I can't figure out if its a code, also I can't find reference to any codes

-On the main board there is a red light that stays on but I think that maybe normal

-Any suggestions on what to check next? or what this could be?




















I assume this is where the Vy is checked?


I assume this is where the Vsc is checked?


Again I really appreciate all help Thanks!!!

[freakaftr8]

Re: LG 60PA5500-UG Plasma, No Picture

If you got something on the screen with the upper disconnectedCheck and see if you have vs voltage with the upper buffer board disconnected. It's so it sounds like your typical damaged plasma panel top ribbon cable because of an inherent design manufacturing problem. Others have had this problem also including myself. If that's the case this TV is not repairable most likely. I have not seen anyone successfully repair a broken ribbon cable

[mouuse25]

Re: LG 60PA5500-UG Plasma, No Picture

Thanks freakaftr8, I pulled the upper buffer and it showed 206 vdc it actually went up a volt might be might common but it did show voltage...Im sure the screens fine when the issue started i could get the LG logo to come up it just went away after a few minutes...Thanks for the help this has me clueless where to go from here

[Nick's Tvs]

Re: LG 60PA5500-UG Plasma, No Picture

My guess is a bad Z-sustain. Check the fuse on the Z it should be blown. If it is not, check the transistors that are screwed into the heat sink for shorts. I have just gotten 2 of these 60" models with no picture issues and the Z was the problem both times. Just in case you don't know/to save time take a multi meter, put it on the continuity setting and or ohms, place both leads on either side of the fuse. If you get Zero ohms/no resistance on your fuse then its good, but if you get O.L reading then its blown. Do the same with the transistors, however with those if you get a short or 0 ohms then that's bad.

[mouuse25]

Re: LG 60PA5500-UG Plasma, No Picture

Thanks Nick's Tvs, well you may be correct with out taking the board off the tv I did a quick test and it seems that I do have a shorted transistor but the fuse seems fine...I'm going to remove the board to do further testing...would you recommend replacing the whole board or just the individual transistor/s?

[Nick's Tvs]

Re: LG 60PA5500-UG Plasma, No Picture

What is the part number of your Z-sus? It should be an EBR number on the sticker.
Also what is the exact location of the transistor? Could you take a picture of it?
I just want to make sure you are not measuring a diode that may look like a transistor. That's an easy mistake to make.

[mouuse25]

Re: LG 60PA5500-UG Plasma, No Picture

Pn: EBR73733601

After removing the board I couldn't get transistors to short out so it may have been a error on my behalf that I thought they were shorted out...I used this method to test them

https://www.utm.edu/staff/leeb/mostest.htm

and to determine the diodes from the transistors I assume the transistors have a board location number that start with "Q" and the diodes start with "D" such as the example below where Q241 and Q404 would be transistors and D242 would be a diode

[Nick's Tvs]

Re: LG 60PA5500-UG Plasma, No Picture

what kind of voltages are you getting between your Y-sus and your buffers?

[mouuse25]

Re: LG 60PA5500-UG Plasma, No Picture

How do I test that?

[Nick's Tvs]

Re: LG 60PA5500-UG Plasma, No Picture

The white connectors between the Y sus and the buffers. Can you get a close up picture of them. Those pins are the ones you will want to measure.
Have you used a DMM before and measured live DC voltage?

[mouuse25]

Re: LG 60PA5500-UG Plasma, No Picture

Yeah I've used a DMM live before I have 600v gloves to protect myself

[freakaftr8]

Re: LG 60PA5500-UG Plasma, No Picture

Dumb question but are all the screws on the y and Z sustain boards in and tight? Lgs don't like having some screws missing. Learned the hard way once on a 60 inch infinia model.

[mouuse25]

Re: LG 60PA5500-UG Plasma, No Picture

That's actually a good question being that it's such a easy thing to over look... I just checked all the screws and cable connections then attempted to power it on but nothing changed...thanks for the mind set since I tend to overlook the obvious rather easily lol

[Nick's Tvs]

Re: LG 60PA5500-UG Plasma, No Picture

Ok so lets measure the VSC pins between the Y-sus and buffers, what do you get on that voltage with the buffer boards connected in and the panel connected in as well. Make sure that all ribbons from the buffers are connected, and all ribbons from the Z-sus are also connected in properly.
be very careful not to short out the pins between one another with the DMM lead as it is easier to do than you think since there is no plastic separation between these pins.
Use chassis ground.

[mouuse25]

Re: LG 60PA5500-UG Plasma, No Picture

I can't get a clear reading it just keeps changing the voltage between -5 to 12 volt I tested each vsc pin I could and tested the vsc test point

[Nick's Tvs]

Re: LG 60PA5500-UG Plasma, No Picture

if your numbers are fluctuating like that then we have an issue with the Y, the buffers or the panel. Just for fun, lets make sure voltages going from the X-sustain/main to the panel are around 87 vdc or so. Not sure what your exact voltage should be on this model, but most plasmas flirt around that numbers for X-sus/main to panel.
If voltages are good and not fluctuating on the X-sus/main side, I would like you to take voltage readings again on those y-sus/main pins but this time with the panel disconnected from the buffers and the X main.
If you still get the same readings, try it one more time with the buffers disconnected from the Y. Make sure to give it at least 5 minutes between each test and to unplug the set every time in order to allow voltages to drop down to a safe level prior to touching stuff in there.
Once you get a reading that no longer fluctuates, what ever you disconnected prior should be the cause of the issue.
Let me know if you have any questions.

[mouuse25]

Re: LG 60PA5500-UG Plasma, No Picture

Okay I just discovered something strange that may be able to help to track down the issue

-I disconnected the X-sus completely and left it disconnected

-Then disconnected the Y-buffer boards from the Y-sus main panel

-Then before plugging the tv in I placed my dmm (+) probe on the vsc test point and (-) dmm probe to chassis ground

-When I plugged the tv in the the dmm showed 65 volt...Then is slowly dropped to zero across about a 2 minutes span

- I let the tv sit unplugged for about 10 minutes and then connected the Y-buffer boards placed (+) probe on vsc again and plugged the tv in and it did the same fluctuation as before

-If I disconnect just the upper Y-buffer the vsc is around 65 volt fluctuates 1 to 2 volt up/down, If I disconnect just the lower its around 85 volt but fluctuates 1 to 2 volts up/down

Is it safe to say my Y- buffer boards are bad?

[Nick's Tvs]

Re: LG 60PA5500-UG Plasma, No Picture

Plug your x main back in completely, and plug your top buffer back in. Turn your set on and check to see if the top half of your set primes. If it does then for sure your lower buffer is bad. If not disconnect the top buffer and check voltages on y-sus going to buffers. If you still get fluctuation then something else is going on. If no fluctuation then I would say replace both buffers.

[mouuse25]

Re: LG 60PA5500-UG Plasma, No Picture

sorry about my hiatus I ordered all new boards to prevent me from taking up to much of the board members time ..and as everyone who has ever ordered anything off ebay soon find out that it turns into a complete mess trying to receive packages 3 out of 6 packages came in broke had to reorder more etc..etc..

I tried what Nick's Tvs said and I get nothing at all even with new buffers the set does not prime at all, I am getting no VSC to the buffer boards it just fluctuates

so here is where I stand now...

I have no VSC or VY reading with or with out the buffers connected...My VA, VS and VZB are all still remaining consistent and in spec...I honestly believe I have received 3 bad Y-Sus boards so I have one more coming

My question now is what controls the VSC and VY voltage?...is it the logic or mainboard by chance?