Zenith Plasma Z42PJ240 sound but no picture

[tom66]

Re: Zenith Plasma Z42PJ240 sound but no picture

Possibly, do remember that a bad Y-sus can kill the Y-buffer too.

[Bamakc]

Re: Zenith Plasma Z42PJ240 sound but no picture

Is the Y-Buffer the long green board to the left of the Y-SUS that is vertical to the screen? If you think the Plasma panel is ok then I will go ahead and order the Y-SUS and Y-Buffer. At this point I only have $25 in this TV and I have really enjoyed this project. Thanks to you it's been like attending training except with my own personal instructor. You have re-kindled my interest in TV repair. I'm very greatfull.

[tom66]

Re: Zenith Plasma Z42PJ240 sound but no picture

Yes, that is the Y-buffer board. It has the small delicate orange ribbons going to the panel on it, and it connects to the Y-sus.
BTW, if you want to get back into LCD/plasma repair a scope is a very useful device to invest in (especially for plasma repair.)

[vinceroger69]

Re: Zenith Plasma Z42PJ240 sound but no picture

tom would a 20 meg scope be ok for basic plasma repairs as been offered one very very cheap.

[tom66]

Re: Zenith Plasma Z42PJ240 sound but no picture

Yeah, as long as it is rated 400V minimum and you can get a 10X probe with it. I used a 20MHz scope on a Panasonic 42" 1080p and it worked fine.

[vinceroger69]

Re: Zenith Plasma Z42PJ240 sound but no picture

great will find out more about it thanks

[tom66]

Re: Zenith Plasma Z42PJ240 sound but no picture

Make sure it's dual channel or quad channel. While you may not need dual channel for some repairs, having it is essential for other stuff like tracing faults in audio amplifiers.

[vinceroger69]

Re: Zenith Plasma Z42PJ240 sound but no picture

ok thanks.

[Bamakc]

Re: Zenith Plasma Z42PJ240 sound but no picture

This afternoon i installed the Y-sus and Y-buffer board that i had ordered. The picture came on with an awesome display running the test patterns. I only let it play for a few minuets. Tomorrow i will apply the power again and let it play for a longer amount of time. This had the sharpest and most vivid picture that i have ever seen on a tv. I have not checked the voltages since replacing the defective boards. How long should i let it run with the test patterns? Is is safe to leave it in the test mode for a long period of time? If this is repaired, then i am extremly pleased with the picture quality and the amount of time and money invested ($80). Thanks Tom66 for your guuidence and assistance in repairing this set.

[tom66]

Re: Zenith Plasma Z42PJ240 sound but no picture

Test patterns can be run indefinitely, however, you should put the case on (even if just 4 screws) as the case is used to guide the warm air through the heatsinks, without that the boards will run hotter than usual. Glad to hear it's working!

Even a budget plasma TV like this will produce a nice image, better than most LCD TVs. I've always thought LG PDPs weren't too bad, but they're losing out to Samsung and Panasonic. In particular, LG PDPs can be tweaked to get a really deep black level from the factory default, if that matters to you.

[Bamakc]

Re: Zenith Plasma Z42PJ240 sound but no picture

When I remove the resistor to stop the test pattern should I have some kind if picture without a video source? The menu doesn't show all I have is a slight glow. I'm sorry about the dumb questions as this is my first Plasma tv ever. Do I need some kind if video source to see even the menu?

[Bamakc]

Re: Zenith Plasma Z42PJ240 sound but no picture

The tv turns off after about 20 to 30 mins when running the test pattern.

[Bamakc]

Re: Zenith Plasma Z42PJ240 sound but no picture

But it will immediately turn back on

[tom66]

Re: Zenith Plasma Z42PJ240 sound but no picture

Power cycling might be part of the test.
However, you should have an image with the test pattern disabled, e.g. "NO SIGNAL".
Have you plugged in the LVDS connector?

[Bamakc]

Re: Zenith Plasma Z42PJ240 sound but no picture

Yes i did. When i first turn on the set the screen lights up with a dim white picture not a bright raster like before then it goes to a dim glow. When i press the menu button i get no image. The volume will increase and decrease. I was expecting a blue screen with no signal or something like that. The test pattern shows all images including full screen red, green, blue and white. The color bar is very vivid and correct. Do you think it could be the board with all of the inputs on it? Thanks, Keith

[tom66]

Re: Zenith Plasma Z42PJ240 sound but no picture

It is looking like it, though I'm not sure why it and the Y-sus/Y-buffer would both fail. Can you show me all the connections around the main board and control board?

[Bamakc]

Re: Zenith Plasma Z42PJ240 sound but no picture

I will take pics this afternoon when i get home from work. Initially i had all voltages on the Y-sus but i think the Z-sus was bad. I think i killed the Y-sus by disconnecting and reconnecting the cable going from the Y-sus to the Z-sus while the tv was on. When i did i heard a snap like a power arc and one of the pins on the connector was black. The lady that gave me this set thought lightning might have came in on it and she just bought her a new on. I dont know what kind of video source she was using at that time.

[tom66]

Re: Zenith Plasma Z42PJ240 sound but no picture

It is normal to hear a pop from the Y-sus after connecting it if the system is still energised, but it is not recommended to do this. The reason is, it may damage the bottom panel drivers which are bonded/glued to the plasma panel, so if they failed, it would be game over... that being said, it's quite rare, and this isn't your problem because you've got good test patterns.

It's funny how prevalent storms are in the US, they seem to kill TVs very easily, yet in the UK, I have only ever seen one device definitively damaged by lightning. I guess it's a difference in intensity. But a surge of high current can easily find its way through the power supply into the signal processing, as well as the Y-sus and Z-sus.

[Bamakc]

Re: Zenith Plasma Z42PJ240 sound but no picture

In my past expierence with tv repair, most of my repairs were either the power supply or the rf module. Lightning would either short the diodes in the full wave bridge rectifier or kill the board that the video source came in on. I have only repaired one LCD ( replaced one open inverter transformer) and i know nothing about Plasma tvs. All my experience was with CRT type sets. And two way radios.

[Bamakc]

Re: Zenith Plasma Z42PJ240 sound but no picture

Here is a pic of the board