Static/Snow Picture on Hitachi Plasma P50X102A

[glutton4punishment]

Hi!

I'm trying to fix this TV (duh!), thanks for your help!

The image has an overall white cast to it with purple and green areas of hue, and lots of snow when there's no input. With input, the image looks like a blend of the image and the the white/green/purple/snow background.

The menus and error message ("no input signal") appears on the screen very clear without problems. The menu and error message appear in a navy blue box with yellow letters, or a black box with yellow letters and a red exclamation point.

All caps/components look good visually, I don't see any burnt out buffers, etc.

What I've done so far is measure voltages:
The values on the sticker say it should be Va=66.7 and Vs=181.7.

Using the pots on the pwr board, I was able to lower the voltages to
Va = 67.4
Vs = 183.4

I couldn't get them any lower, and I understand that we should try to get within 0.2V of the target. The Vs was as low as I could get them to go. I had my daughter watch the screen as I adjusted the values, and she said she didn't see any difference before and after my voltage adjustments.

I pulled a 680uF 100V cap from the power board that was near the adjustment pots, and it read within the 20% tolerance (607 uF), but the ESR was 0.3.

I'll post pics in a few minutes.

Really hoping I can save the day with this one with your help!

[glutton4punishment]

Re: Static/Snow Picture on Hitachi Plasma P50X102A

some pics

[glutton4punishment]

Re: Static/Snow Picture on Hitachi Plasma P50X102A

bump

[R_J]

Re: Static/Snow Picture on Hitachi Plasma P50X102A

It looks like there are 2 damaged resistors near C652 on the power supply board, or is that just markes on them?

[glutton4punishment]

Re: Static/Snow Picture on Hitachi Plasma P50X102A

It looks like there are 2 damaged resistors near C652 on the power supply board, or is that just markes on them?

Thanks RJ, but it's just black magic marker marks

[R_J]

Re: Static/Snow Picture on Hitachi Plasma P50X102A

It does look like a z-sus problem, Check the Y & Z boards for any open fuses (they might be small green pico fuses)
Hitachi plasmas were not very popular, (expensive compaired to other makes) so there is not much information on them, the boards are also very complex using discrete components.
The power supply might have a problem as you should be able to adjust it lower. or it could be due to not being under proper load because of a z-sus problem.
What meter are you using as some meters don't like checking the VS & Va voltage on plasmas.

[glutton4punishment]

Re: Static/Snow Picture on Hitachi Plasma P50X102A

It does look like a z-sus problem, Check the Y & Z boards for any open fuses (they might be small green pico fuses)
Hitachi plasmas were not very popular, (expensive compaired to other makes) so there is not much information on them, the boards are also very complex using discrete components.
The power supply might have a problem as you should be able to adjust it lower. or it could be due to not being under proper load because of a z-sus problem.
What meter are you using as some meters don't like checking the VS & Va voltage on plasmas.

thanks, RJ!

To help me hunt down the fuses on the Y&Z boards, am I correct that they will be marked with an "F" on the circuit board?

I have 2 DVMs, a newish one, a Vichy VC97, and an old Radio Shack (I lost my analogue VM). I pretty much use only the Vichy nowadays.

[R_J]

Re: Static/Snow Picture on Hitachi Plasma P50X102A

It could be the meter reading the voltage wrong, any high frequency signal present on the Vs line can throw off the reading. This may not be the issue but it could be.
I have a similar LG/goldstar meter does not like reading plasma tv Vs. it often shows OL even on the 2000v scale. My fluke reads the voltage correctly.
I do see a couple over heated electrolytics (covers have shrunk) on both the Y and Z boards

any fuses should be marked "F". Are you sure about the model number? I can't find anything on that model.

[glutton4punishment]

Re: Static/Snow Picture on Hitachi Plasma P50X102A

It could be the meter reading the voltage wrong, any high frequency signal present on the Vs line can throw off the reading. This may not be the issue but it could be.
I have a similar LG/goldstar meter does not like reading plasma tv Vs. it often shows OL even on the 2000v scale. My fluke reads the voltage correctly.

I do see a couple over heated electrolytics (covers have shrunk) on both the Y and Z boards

any fuses should be marked "F". Are you sure about the model number? I can't find anything on that model.

Thanks for putting in the effort, RJ!!

But yeah, I'm sure that's the correct model #. Nothing on any of the boards or stickers on the frame gives any indication of being manufactured by somebody else.

I went through some the power supply board, and although the ESR's of the caps seem to be high, I'm not sure where the problem is.

WOW! I guess I have A.D.D.! Your comment about the caps with the "missing half of the shrink wrap label" went right by, and it didn't even register! I was WONDERING why some of the caps looked like that! OK, I guess they're next on the list to check out.

Once I put the PS board back in, I'll take another picture, maybe that will help the diagnosis......

[glutton4punishment]

Re: Static/Snow Picture on Hitachi Plasma P50X102A

I put back in the power supply board and took pics of the screen with input from a laptop.

(Before I get to the pics, I pulled the caps from the Y-sus board that had shrunken labels on them. The values were within specs, but the ESR's read around 0.5.)

I guess I want to make a couple of comments about picture quality that may give you guys clues.

1. There seems to be a burn in at the top right and left corners, and towards the bottom in the middle. Once we get the big picture fixed, we'll work on that.

2. When the menu screen or error messages are displayed, it seems as if the picture is great.....maybe b/c of a black background? Maybe because the source of the signal is a different board??

3. On the screen, where there should be white, there is a shade of purple, and the purple carries on in a horizontal direction to the left and right of the white area.

4. If you look at the display control panel pic, it looks good. Aside from this, there seems to be a purple/lilac snow/static across the whole screen.

Again, when the screen displays Hitachi menus/etc. the image seems very good.

4. This may be something new b/c I don't remember it, but the bottom left has horizontal black lines. It could be b/c I re-seated a ribbon cable on the Y-sus board.

Thanks, as always, for your help!

[R_J]

Re: Static/Snow Picture on Hitachi Plasma P50X102A

The thin black lines at the bottom of the screen are likely a result of the flex cable from the panel to the buffer board not seated properly. Reseat the lowest cable, If this does'nt change the black lines you likely have a bad buffer ic.

[glutton4punishment]

Re: Static/Snow Picture on Hitachi Plasma P50X102A

yeah, I'm sure it's the flex cable seating.

any other ideas about the purple and purple banding?

Or why the menu screen looks good?

[R_J]

Re: Static/Snow Picture on Hitachi Plasma P50X102A

There is very little information on this model, I would be concerned about not being able to adjust the Vs and Va. low enough. You should be able to adjust the voltage lower than the panel sticker. If you have access to another meter, ie: fluke, recheck the voltage. Also check that your meter battery is good, and not low, if it is low you could get a wrong reading.
If the voltage is indeed high, that is likely the problem.
One thing you can try is measure the Vs voltage on the power suply board, then measure the Vs voltage on the plug on the Y-sus or X-sus board. It should remain the same, and does'nt read higher near the y,x boards

The picture will look better with a low intensity image like the menu, the more intensity (bright white) will usually show up that way. The voltage setting is important in plasma's

[glutton4punishment]

Re: Static/Snow Picture on Hitachi Plasma P50X102A

Thanks again, RJ, I'll do as you said.