zenith Z50P3 PLASMA TV screen issues pink and purple grainy no image

[tw2005]

Re: zenith Z50P3 PLASMA TV screen issues pink and purple grainy no image

ill have to resarch how to test for short on them i forgot

I think so, I just don't know the LG stuff well enough, see what you find with the 5v rail, the buffers definitely won't pass data without it.

[shelby5041]

Re: zenith Z50P3 PLASMA TV screen issues pink and purple grainy no image

when i get time i will review my y buffers...i ruled them out when i boguht new ones but there is a possibility like u said that maybe they could be part of issue....

[shelby5041]

Re: zenith Z50P3 PLASMA TV screen issues pink and purple grainy no image

wow the buffers are really cheap on ebay like 10-20.00 each

i may just go ahead and buy another set of ys to continue my troubleshooting...afger i find more about the 5v test

[tw2005]

Re: zenith Z50P3 PLASMA TV screen issues pink and purple grainy no image

sounds desparate, surely it's possible to test them.

[shelby5041]

Re: zenith Z50P3 PLASMA TV screen issues pink and purple grainy no image

odd..my buffers are ebr38447802 and 602

shop jimmy does not show these part #s for z50p3

they have diff part#

[tom66]

Re: zenith Z50P3 PLASMA TV screen issues pink and purple grainy no image

5VF is floating, test wrt to the screws on the Y-sus or the VFG output.
Every signal to the buffers is floating, it's not relative to chassis.

[tw2005]

Re: zenith Z50P3 PLASMA TV screen issues pink and purple grainy no image

They both have the same PCB, the style of ribbon connector used looks slightly different but I'd expect both would work

[shelby5041]

Re: zenith Z50P3 PLASMA TV screen issues pink and purple grainy no image

thanks....so i test 5v to y buffer by grounding to a screw on y board?....if so i did that 0v.....

or do i test using pin marked gnd like tv2005 said?

[tom66]

Re: zenith Z50P3 PLASMA TV screen issues pink and purple grainy no image

The output of the Y-sustain, the un-grounded screws connecting the board OR the connectors which have lots of pins connected together.

You've not posted any clear photos of the Y-sus, so I'm suggesting possible configurations... I don't know how your set is laid out.

[tw2005]

Re: zenith Z50P3 PLASMA TV screen issues pink and purple grainy no image

I think it's going to be this layout Tom.

[tom66]

Re: zenith Z50P3 PLASMA TV screen issues pink and purple grainy no image

Yuck, IPM based. The two outer pairs of screws are the VFG. The inner pair will be the VFG+VSC (about 120~150V above VFG). The 5VF is 5V above VFG, approx.

[tw2005]

Re: zenith Z50P3 PLASMA TV screen issues pink and purple grainy no image

Is there any point maybe adapting this later model test to this using the pin designations to match?

[tom66]

Re: zenith Z50P3 PLASMA TV screen issues pink and purple grainy no image

I would just test the output nodes using a continuity meter, test to VFG and VFG+VSCN. Inputs on the IC itself are unlikely to fail.

[tw2005]

Re: zenith Z50P3 PLASMA TV screen issues pink and purple grainy no image

I would just test the output nodes using a continuity meter, test to VFG and VFG+VSCN. Inputs on the IC itself are unlikely to fail.

That's certainly the quick and easy way, well what I'd do. So the gnd and 5v at p2 to the buffer, that won't display 5v? I've never probed a live buffer, only ever resistance.

[tom66]

Re: zenith Z50P3 PLASMA TV screen issues pink and purple grainy no image

VFG to 5VF should give about 5V, but GND to 5VF (with GND being chassis) will just give a nonsense number because you're essentially just measuring the Y-sus output plus 5V... and the Y-sus output is not a DC level but a complex multi-step waveform and it changes based on the current image.

[tw2005]

Re: zenith Z50P3 PLASMA TV screen issues pink and purple grainy no image

VFG to 5VF should give about 5V, but GND to 5VF (with GND being chassis) will just give a nonsense number because you're essentially just measuring the Y-sus output plus 5V... and the Y-sus output is not a DC level but a complex multi-step waveform and it changes based on the current image.

I'm not sure if gnd at the ysus out to the buffer is chassis or floating on that 12 pin lead, but I get your drift.

I guess you've done little with these too? Nothing leaping out from the photos or what's been done?

[tom66]

Re: zenith Z50P3 PLASMA TV screen issues pink and purple grainy no image

I'd like to probe those signals sometime, but it would require a high speed differential scope probe. Which I don't have. Would be useful for tracking down odd faults with Y-buffers.

[tw2005]

Re: zenith Z50P3 PLASMA TV screen issues pink and purple grainy no image

I'd like to probe those signals sometime, but it would require a high speed differential scope probe. Which I don't have. Would be useful for tracking down odd faults with Y-buffers.

ok, thanks

[shelby5041]

Re: zenith Z50P3 PLASMA TV screen issues pink and purple grainy no image

update with tv powered on i checked pin 2 5v to pin 1 ground on power cable from y to y buffer...reading 0v

also did same 5v and neg to the metal connector thay atyaches both boards...reading 0v

also did resistence test pin 2..pin 1...reading 0...or no reading

[shelby5041]

Re: zenith Z50P3 PLASMA TV screen issues pink and purple grainy no image

correction resistance