Zenith Z42PX2D - plasma - audio, no video

[whitejohnny71]

Hi Folks, looking at a Zenith 42" model Z42PX2D. The unit powers on with a black\blank screen. Tiny little sparkles of red and green can be seen randomly around the screen. I hear open channel static and the volume controls work. The channel button cause the audio to mute for a moment so it appears to be working. (I don't have cable tv or a signal source at the moment so I haven't tried to verify that further). So it seems the power supply and the mainboard are ok.

I measured all regular and smd fuses visible and all are good. All power supply output voltages measured correctly.

I have some tools - hot-air rework tool and soldering iron, 20meg scope and voltmeter. I routinely repair laptop motherboards with and without schematics as well as lcd monitors and other consumer electronics (car stereo amps, etc) so I'm not clueless, but I just don't do enough plasmas to know what I'm looking for.

So all help appreciated! Where do I start?

I have attached pics of the boards and the overall set...

[whitejohnny71]

more info

Also, on the left side, the 3 metal plate power connectors between the y-sus and buffers measured -32, +17 and -32 to ground. I've circled them in the attached pic.

[whitejohnny71]

Re: Zenith Z42PX2D - plasma - audio, no video

I have the service manual. Is it possible for this symptom to occur if the voltages are out of alignment?

Hmm, ok, aligned at Va=65 and Vs=184, off then on, no change. Hit power button, green led blinks 5 times, 3 seconds later, hear audio static but no picture.

[whitejohnny71]

Re: Zenith Z42PX2D - plasma - audio, no video

From what I've read, can I pull the lvds feed to see static like with an LCD or should I net do that? Def not trying to make anything worse.

[Alastair E]

Re: Zenith Z42PX2D - plasma - audio, no video

Set off--pull the LVDS cable from Control-board, locate the test-points (depends on whether LG or Sams. panel,where and how, Looks like a 42V6 LG to me) and short the two.

Power-up, panel should display various test-patterns on a continuous loop.

If not, you have either a control, X-sus, Y-sus or PSU fault.

--Looking at that set, it has IPM's These are the most likely cause of problems. Scope-tests will indicate which is faulty, as well as the condition of the Vs fuses....

[whitejohnny71]

Test points - LG panel

Hi, thanks for your help Alastair. Yesterday after reading about the test points in another Zenith thread, I checked but couldn't find anything in the service manual.

The panel is an LG PDP42V7. I had to remove it from the table for lunch (my office workbenches are full at the moment) but I will check the last digits later. I've attached a pic of the stickers.

Any idea where the test points are?

[Alastair E]

Re: Zenith Z42PX2D - plasma - audio, no video

Oops--Sorry, Its a 42V7.

Same advice applies though....

[whitejohnny71]

Re: Zenith Z42PX2D - plasma - audio, no video

I'll prob not be back to it for a day or so (i normally do laptops and desktops; gotta keep the flow going) but if anyone is familiar with this model or the 42v6 if you could let me know where the test points should be I'll try that as soon as I can get to it. Its my understanding anything between 100 and 470 ohms between the points is ok right?