Hitachi plasma dark picture with figures highlighted in red

[Cornboats]

Hitachi 42PD4200

This sets has main board components supplied by LG.

I Can't get to the bottom of this one and its driving me nuts.

First Z-sus blew so I changed IPM.
Picture was ok but its ipm was running so hot it would have burnt out had I left it on for more than 5 minutes.

Second - Found 15v rail from y-sus was decreasing from switch on down to 9v.
This corresponded with the Z-sus ipm increase in temperature.

I changed the Y-sus board , got a good 15v rail and good picture.
Result-Yes .

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

I looked up trouble shooting guide for inspiration and it says to check Y drive buffers. Theres 2 testpoints near to the bottom drv outlet. Can'tmake out in guide wether these are for a diode check. Testing is infinite both ways anyway.

Could it be the buffers?

Oh and the 15 v rail is now down to 14V.

[tom66]

Re: Hitachi plasma dark picture with figures highlighted in red

I would adjust -Vy and Vscn to their labelled voltages on the panel sticker.

I can pick up a similar 42" at my local tip for £30 in working order (it's only an SD plasma), so I wouldn't recommend spending too much on it.

[Cornboats]

Re: Hitachi plasma dark picture with figures highlighted in red

I'm a bit unsure about doing this as I've only ever adjusted Va & Vs voltages.

Are these adjusted using digital multimeter or do I have to use a scope?

These are on the Y-sus board -right.

There are resitors marked VSCW, -VY and V setup. Does it matter which side of resitors probe goes?


We can't buy anything from out tips in U.K. "Strictly forboden."

[tom66]

Re: Hitachi plasma dark picture with figures highlighted in red

I'm a bit unsure about doing this as I've only ever adjusted Va & Vs voltages.

Are these adjusted using digital multimeter or do I have to use a scope?

You can use a DMM. Post a picture of your Y-sustain board and I will highlight where to test.

There are resitors marked VSCW, -VY and V setup. Does it matter which side of resitors probe goes?

You will usually need to probe -across- the resistor. The polarity is not important, only the magnitude of the voltage.

We can't buy anything from out tips in U.K. "Strictly forboden."

I can here, but only on certain days and it costs me more in most cases than buying directly from people. I saw someone on Gumtree recently listing a 50" standard definition (i.e. 853x480) plasma for £60.

I got my nice (faulty, 4 bad caps, easy fix) 42" LG LCD TV from there, along with a few other small things, but now I don't really bother there.

[Cornboats]

Re: Hitachi plasma dark picture with figures highlighted in red

Heres photo of y-sus.

I can see blue potentiometers top right and test resistors just below.

The label is marked

Va;65V/Vs190V
200/-70/120/NA/NA

[tom66]

Re: Hitachi plasma dark picture with figures highlighted in red

Do you have a picture looking directly down on the Ysus - it's difficult to see any labels.

[Cornboats]

Re: Hitachi plasma dark picture with figures highlighted in red

Cameras useless for close ups I'm afraid.

check these out.

[tom66]

Re: Hitachi plasma dark picture with figures highlighted in red

Okay so those three yellow transformers are your sub supplies, nearby there should be some test points. Test as indicated and adjust the voltage to match panel sticker.