Hitachi plasma intermittent ghosting

[Cornboats]

Hitachi plasma 42PD4200

I've got an intermittent picture fault. Full sharp colour picture goes to blur and ghosting for 5 seconds and then back to full colour.

I thought it was LVDS board but swopped and no difference made.

VA & VS voltages spot on.

Any ideas would be welcome.

[tom66]

Re: Hitachi plasma intermittent ghosting

Cold solder joint for Vs on Z-sustain. Does picture get dim during ghosting? Slight purple/lilac tint? Do you have a video?

[Cornboats]

Re: Hitachi plasma intermittent ghosting

Hi thanks for replying. Yes looks like picture looses focus and predomant colour becomes pink/orange hue.

Its interesting that you went straight for the Z-sus because last year I had to change the z-sus ipm. I wonder if my soldering is suspect. mm I'll strip the board and and go over all the joints.

I'm here to learn- What told you to go for VS on Z sustain board?

I could try and take a vidio of the picture but it doesn't stay on long so I'd have to wait and watch for some time.

[tom66]

Re: Hitachi plasma intermittent ghosting

On LG PDPs the Z-sustain is responsible for sustaining the display (making it light up), and it also assists with the erase and set process. Without proper sustain, the PDP doesn't convert the UV (from the neon/xenon discharge) to visible light entirely, leading to a distinct purple tinge to the image (and usually reducing the brightness.) It works in turn with the Y-sustain. Without the erase and set the PDP won't change fast enough.

Vs is needed for both of these features so without it the picture will go blurry and dim. It might not be a cold solder joint - could be a loose connector too.

[Cornboats]

Re: Hitachi plasma intermittent ghosting

Thanks for info. I'llget back to you after I've done the checks.

[Cornboats]

Re: Hitachi plasma intermittent ghosting

I've stripped it down checked and re-soldered and put it all back together only to find the same fault.

This time I kept the set on for 15 minutes whilst checking Va and VS. I had to turn it off then, the picture was fading and the heat coming off the Z-sus ipm was too much to be acceptable. So I've come to the conclusion this is where the problem is.

Now I bought the set because it was faulty and found the Z sus ipm had burnt out.
I bought a replacement from StartBoy1010- Ebay USA.
It got hot as soon I'd fitted it so I put the set under the bench for further investigation-till now.

Assuming its not a faulty IPM - because the original burnt out, so I'm thinking what caused it to burn out?

What is there on the board that would make the ipm run hot? I don't know how the boards work - Do you?

[tom66]

Re: Hitachi plasma intermittent ghosting

The IPMs -do- run very hot. It's a common problem with LG PDPs, and it's part of the reason they die so quickly. There's little you can do about it, other than maybe turning down Vs by 3-10 volts (the picture will be slightly dimmer, but barely noticeable.)

By the way the panel resolution is only 853x480 pixels, so in general I wouldn't spend much on it - you can get working used plasma monitors with this resolution for around £50 on eBay.

[Cornboats]

Re: Hitachi plasma intermittent ghosting

I know they run hot- about 70 deg c would be fine. But this ones in excess of 100 c and climbing with a reducing picture- so something not right. Maybe theres a voltage regulator on the board thats not giving correct output.

I'll hunt round for a z-sus board and change.

[kc8adu]

Re: Hitachi plasma intermittent ghosting

check the 15v to z.
i have seen this off and cause repeat failures of the ipm.
i assume this is really a lg?

[Cornboats]

Re: Hitachi plasma intermittent ghosting

thanks for your reply.

Its using LG Z, Y & buffers.

15v rail is from Y sus I think.

I'll check it out and let you know.

[Cornboats]

Re: Hitachi plasma intermittent ghosting

The voltage on P3 on the z-sus -marked 15v is 11.7v-11.9v.

Now I've got a problem because I thought this was derived from the Y-sus board but P3goes to the bottom left buffer board. Unless the 15v supply is connected through all the buffer boards back y-sus.

[Cornboats]

Re: Hitachi plasma intermittent ghosting

I changed the Y-sus board. This then provided constant 15v supply and gave good picture. I ran for 2 hours.

It didn't last though. When I switched on again there was picture and sound but picture is very dark and figures are highlighted in red.

I'm going to start a new thread with this new problem.

Thanks to all who have contributed to this one.