Samsung PN42B400P

[capkid]

I'm working on a Samsung plasma (PN42B400P) that has sound but no picture.

Here is the sequence of events to this point and some tests I performed:

Sequence of events:

(1) SMT component on Y-main was broken by previous owner who removed the Y-main and X-main, so I replaced the Y-main (ShopJimmy).
(2) After replacing the Y-main, the VS and VA voltage would drop when the powering on the TV. I disconnected the Y-buffer - voltage stayed up.
(3) I replaced the Y-buffer (ShopJimmy), but I still got no picture. I then noticed that the 1A 125V pico fuse for the 15V circuit on the X-main was blown (not sure if it was blown when I picked up the TV). I replaced the fuse and continued on with the following tests:

(1) Power supply only - VS, VA, and 15V stable
(2) Power supply and Y-main connected - VS, VA, and 15V stable
(3) Power supply, Y-main, and X-main connected - VS, VA, and 15V stable
(4) Power supply, Y-main, X-main, and X-buffer connected - VS, VA, and 15V stable
(5) Power supply, Y-main, Y-buffer, X-main, and X-buffer connected - VS and VA voltages dropped. 15V remained stable.

Any ideas? Could I possibly have a bad panel?

[cliff_hootarski]

Re: Samsung PN42B400P

So the VS and VA dropped when you have everything connected. Disconnect the flex ribbon cables going into the panel from the Y buffer board and see if the voltages stay up. (Obviously disconnect with the set powered down). Wouldn't leave it powered up very long like that.

[Glitcher]

Re: Samsung PN42B400P

Check for cracks on the internal screen of the plasma. If the set was attempted to be repaired by someone else its possible that he/she might of figured out its not repairable since after removing the y and x main.

[capkid]

Re: Samsung PN42B400P

Ok, I found about six components that were bad on the X-main. Dummy me...I fell into the lazy trap of just replacing the fuse in the X-main without checking the board's components - thought the VS and VA voltage drop was caused solely by a bad Y-buffer I also found a blown component on the X-main buffer (top blown off it). This is turning out to be a more expensive repair than I figured.

[capkid]

Re: Samsung PN42B400P

The TV is all put back together. However, the power button that's incorporated in the bezel seems to work intermittently. Has anyone run into this issue?

[tom66]

Re: Samsung PN42B400P

Is it one of those touch sensitive ones?

[capkid]

Re: Samsung PN42B400P

Is it one of those touch sensitive ones?

Yes, it is.

[tom66]

Re: Samsung PN42B400P

Remove the board and check if pressing on the pad directly works. If not the board may be dirty or faulty. If it does work then it may not be properly secured down or the plastic may be dirty.

[capkid]

Re: Samsung PN42B400P

Remove the board and check if pressing on the pad directly works. If not the board may be dirty or faulty. If it does work then it may not be properly secured down or the plastic may be dirty.

Yesterday, I gave the bezel a couple light taps, thinking that maybe there was some corrosion buildup. The button seemed to respond right away.

[capkid]

Re: Samsung PN42B400P

Samsung must be churning out some junk TV's in recent years. I picked up my 5th of these thin-profile Samsung TVs today. It was evident that the Y-main was bad, as there was a burn mark on the back side of the panel under the Y-main. I found something like 8 shorted components on the Y-main, including two badly burned SMT resistors and a burned SMT cap.

[tom66]

Re: Samsung PN42B400P

Well, yeah, we know that . Tell us something we don't know!
I'm not sure how Samsung get away with it...
"Friends don't let friends buy Samsung" - a user on here, very apt!

[capkid]

Re: Samsung PN42B400P

Well, yeah, we know that . Tell us something we don't know!
I'm not sure how Samsung get away with it...
"Friends don't let friends buy Samsung" - a user on here, very apt!

LOL. Yeah, I guess I was just a little incredulous at some of the Samsung junk I've encountered recently. I knew Samsungs had issues, but geez. I'll stick with my Panasonic, thank you very much.