Zenith Plasma Z42PJ240 sound but no picture

[Clydeuk]

Re: Zenith Plasma Z42PJ240 sound but no picture

If I can just jump in quickly, sorry I haven't followed the thread right through but I have a set with an LG PDP that was suffering sparkles (maldischarge). I flashed in a new ROM on the CTRL board as advised by the LG documentation, and ended up with an identical fault to what you have, no menu's, very faint glow from the display. When I enabled the test patterns (moving a resistor on CTRL board in my case) they displayed perfectly (sparkly still but all working and correct). I knew the main board was ok as I hooked it up to another PDP I had been working on. I tried both ROM files LG provided, the other one gave me nothing at all.

When i flashed the original file back in it worked as before. Is it possible your CTRL board is faulty? A scope would help here as you could check for LVDS signals.

[Bamakc]

Re: Zenith Plasma Z42PJ240 sound but no picture

Thanks for the info. I dont have a scope or access to one. Is the CTRL board the one that has all of the inputs on it? If i replace this boad will i have to have the ROM flashed with different firmware?

[Clydeuk]

Re: Zenith Plasma Z42PJ240 sound but no picture

Hi bud, your CTRL board is the one attached to the panel, the one you used for running the built in test patterns, connecting to both sustain boards each side and also the bottom drivers. It will have the LVDS input connector as well that comes from the main board. I wouldn't be too bothered about firmware at this stage, if you are going to replace it try and get one of the same part number. I'm wondering whether the ROM got corrupted considering you thought it may have had a surge trauma.

I can't be certain here obviously and wouldn't want you spending out unnecessarily. If you wiggle the LVDS connector when the set is powered up do you get any response from the screen? It's safe to pull in and out while the set is powered up as it's only carrying low voltage data.

[tom66]

Re: Zenith Plasma Z42PJ240 sound but no picture

While it is possible for a power surge to damage the control board and still leave it able to output test patterns, it is unlikely. And corrupting the firmware would be even more unlikely; if it's going to damage something, it's going to damage the LVDS input port.

It's very hard to determine whether the problem is with the main or control when you have sound. I'd personally be leaning towards the main, but I make no guarantees. You'd have a similar issue with an LCD TV, being unable to determine if it is a main board or T-con (control) board fault.

[Bamakc]

Re: Zenith Plasma Z42PJ240 sound but no picture

Thanks for your info. I ordered a main board yesterday morning and i should receive it by this weekend. If this dont fix it, i will order the control board. I am having too much fun to quit now. This is a summary of my first Plasma TV repair. When i first got the set it would come on and have a bright white raster just like an old CRT type tv with no antenna connection, then in about 3 seconds the picture would go dark but the audio would still be there. I had all of my voltages on the Y-sus, power supply and i thought the Z-sus as well. When i disconnected the cable going from the Y-sus to the Z-sus while the set was powered up, then reconnected it, it arced and that's when i found shorted components on the Z-sus. I replaced the Z-sus and put it in test mode and had a very distorted and incomplete picture, so i replaced the Y-sus and Y-buffer and now have an awesome picture in test mode. Whenever i take out the resistor, i have a dim lit screen with no response to the menu. I am positive that i will only try to repair TV's as a hobby. I would starve trying to do this as a business. lol

[Bamakc]

Re: Zenith Plasma Z42PJ240 sound but no picture

Tom66, You have been 100% correct from the beginning. I received the Main Board and installed it and the picture looks great except for one thing, the picture is off center when i display the menu. I couldn't find any adjustments in the menu or the board to correct this so i removed the board to look on the back and noticed that there was an EPROM with a lable that had Z50PJ240 and a version and date code on it. I looked at the back of my old board and it had Z42PJ240. After doing some searching i found that the board that i had ordered is for a 50 inch TV. The only part number that i could see on both boards was the same. So i guess that would explain the picture being off center. Is the EPROM on the back of the board the only difference and if so can i swap it from my old board? If not i'll order the correct board and this will be fixed.

[tom66]

Re: Zenith Plasma Z42PJ240 sound but no picture

Brilliant to hear!

The 50" plasma panel is 1366x768 and the 42" is 1024x768. So, the panel resolution is different and some of the picture is missing because the 42" can't display it all. You will need to order the 42" board. While it could be a simple EEPROM I wouldn't take the chance of mucking up a good board such that you can't return it.

There's no need to order the Zenith board. You can also order the equivalent LG board. As long as it was used with a PDP42T1 panel, there should be no issue.

[Bamakc]

Re: Zenith Plasma Z42PJ240 sound but no picture

Tom, again many thanks for your guidence and training in repairing this tv. You have given me a basic understanding of Plasma tv's and what each circuit board is designed for. I bought all of my boards off ebay, so i guess i will try and sell it for the $28 that i gave for it. At least i can positively say that it's a good working board. Thanks again. Keith