PN42A400C2D issue

[tom66]

Re: PN42A400C2D issue

OK, do you see a point marked Vg or 15V? Does that measure around 15V with the X-main connected?

[CLANKIRKPATRICK]

Re: PN42A400C2D issue

My bad...there is sound

[CLANKIRKPATRICK]

Re: PN42A400C2D issue

i checked the fuse on the y main and it reads 0.9

[capkid]

Re: PN42A400C2D issue

Is that 0.9 ohms at the Y-main fuse? Also, there should be VSC (on Y-main) and VE (on X-main) voltage specs on the panel label where VS and VA are displayed. Since you have sound, I'd measure those voltages. There should be a test point on each of the mains for their corresponding voltages.

Edit: VSC is labeled as "VSCAN" on the Y-main. The test point is near the CN5005 connector.

The VE test point on the X-main appears to be the R4003 resistor, but I can't see it clearly in a pic I was reviewing. If that is the correct point, you need to place your neg probe on one lead of the resistor and your pos probe on the other lead.

[CLANKIRKPATRICK]

Re: PN42A400C2D issue

Yeah, .9 ohms on the y fuse....the -vsc is fluctuating between -55 an -80....the ve is steady at 95.4

[tom66]

Re: PN42A400C2D issue

You have a bad Y-main or buffer board then. Isolate the Y-buffer and check -Vy again. If it is still fluctuating, the Y-main is bad.

[CLANKIRKPATRICK]

Re: PN42A400C2D issue

I tested the VSCH on the y board, is the v scan the screw?

[CLANKIRKPATRICK]

Re: PN42A400C2D issue

how do I isolate the Y- buffer?

[tom66]

Re: PN42A400C2D issue

Disconnect it from Y-main, leave it connected to the orange ribbons on panel. Be very careful not to damage/break orange ribbons as these are for the plasma panel module and cannot be replaced if damaged.

[CLANKIRKPATRICK]

Re: PN42A400C2D issue

I found the v scan and it fluctuates from -184 to -194 volts

[CLANKIRKPATRICK]

Re: PN42A400C2D issue

how do I disengage the connections between the buffer and the y main? The white ones..

[CLANKIRKPATRICK]

Re: PN42A400C2D issue

The both vsch and vscan voltages are stable after removing the buffer, does that mean its a bad buffer board?

[tom66]

Re: PN42A400C2D issue

Most likely. You can look carefully at the buffer ICs, if you see any burn marks or holes blown in them they are definitely bad.

[CLANKIRKPATRICK]

Re: PN42A400C2D issue

So I changed out the Y-buffer today and still have the same problem with the fluctuating voltages on the Y-main. Any thoughts?

[capkid]

Re: PN42A400C2D issue

I'd try testing a few components on the Y-main with the board removed from the TV. This Y-main may be a little different from some of the other Samsungs that exhibit failures of the heat sink components when the board is bad. If you find a bad component, I'd replace the Y-main AND the Y-buffer again.

[CLANKIRKPATRICK]

Re: PN42A400C2D issue

What components exactly? Are you saying I need to buy another buffer in addition to the new one I just bought when I change out the y main?

[capkid]

Re: PN42A400C2D issue

I can't tell exactly which components from pics, but there should some transistors and diodes on the heat sinks. I'd personally replace the Y-buffer again if the Y-main proves to be faulty. I haven't found a reliable way to test the buffers, and you risk the Y-buffer killing a replacement Y-main - infinite loop.

[CLANKIRKPATRICK]

Re: PN42A400C2D issue

So just hooking up a new y buffer to a faulty y main kills it, and it needs replaced again?

[tom66]

Re: PN42A400C2D issue

In some cases; that being said I've only ever heard of it on older Samsung and LG plasma panels, not on newer ones, I wouldn't entirely rule out the chance.

[CLANKIRKPATRICK]

Re: PN42A400C2D issue

That is really frustrating that I killed the brand new buffer just by hooking it up...so should I take the chance on just getting a new Y main or do I need to get yet another y-buffer to go along with it?