Samsung ps50c490 plasma TV half image

[Dannyx]

Good day folks. I got this Samsung plasma TV on my hands which only displays picture in the lower half of the screen. The top half only displays some random artefacts, so it's not totally dead. I must admit I haven't worked with too many plasma displays, since they began fading out by the time I began tinkering with electronics, so I can't tell for sure what the defect might be, (outside very obvious defects like a totally dead set which would point me to a PSU issue). I took some very brief measurements and couldn't find any immediate shorts. Perhaps one of those chips on the Y buffer is dead ? Couldn't find a service manual either to know what the VE VS voltages are supposed to be, though I'm assuming those are correct since there is clear picture in the bottom half.

The TV looks deceivingly simple on the inside: the boards are nicely laid out and you can easily tell which is which, so I personally have my money on the top buffer board being defective one way or another. Now I'd just need an expert, or at least a person who's played around with plasmas more than I have, to confirm my theory and then we'll go from there I suppose. Any help would be greatly appreciated.

Pictures are horrible, do apologize for that, I took them in a hurry without too much effort, but if you do require clearer pictures or close-ups, please feel free to ask

[Dannyx]

Re: Samsung ps50c490 plasma TV half image

Ok, I'm an idiot: the voltages the panel expects are written on a label on the chassis. Measured those and they're within spec, so the more I measure around, the more I believe it's the Y buffer.

[mmartell]

Re: Samsung ps50c490 plasma TV half image

That is a strange one. Is the fault exactly half of the screen ?

That program material doesn't help either. Try taking a pic with something that we would recognize what the top half should be.

[Dannyx]

Re: Samsung ps50c490 plasma TV half image

That is a strange one. Is the fault exactly half of the screen ?

That program material doesn't help either. Try taking a pic with something that we would recognize what the top half should be.

Yes, it's precisely half the screen. If I disconnect the top buffer ribbons, the horizontal stripe which corresponds to that ribbon becomes black, as it should, but doesn't affect the remainder of the faulty area.

[attainteddragon]

Re: Samsung ps50c490 plasma TV half image

i'm not sure if you can get away with just disconnecting just one of the ribbon cables that goes to the panel or not on this set. maybe someone else can clarify if it is ok or not.

[Dannyx]

Re: Samsung ps50c490 plasma TV half image

If one of the chips is faulty, disconnecting the ribbon cables makes no difference, since the chip is still there IMO. THIS video describes how to troubleshoot a similar issue on a fairy similar TV, though my Y buffer is slightly different and I couldn't measure the voltage drop across the resistors the guy mentions: my meter just display random stuff, almost like it's bugging out. My guess is that the buffer is not entirely identical and the signal on those resistors differ from the one the guy shows, despite the boards looking similar.

Poking the board and buffers made no difference either BTW.

[Dannyx]

Re: Samsung ps50c490 plasma TV half image

I noticed the third chip down from the top of the Y buffer gets rather hot rather quickly after startup. It belongs to the area that's faulty, so could this indicate a faulty chip or a faulty panel ? Either way, I don't think I'll carry on trying to repair this thing: can't find a buffer board locally at an affordable price and I'm assuming replacing the individual chips wouldn't be cheap/easy either...That doesn't mean we have to stop here - the discussion carries on

[Andrew F. Ali]

Re: Samsung ps50c490 plasma TV half image

That is correct. Faulty chip/s. Your panel is OK. Easy fix if you can get the components to fix the Bd. Or just buy another working Bd.

[Dannyx]

Re: Samsung ps50c490 plasma TV half image

That is correct. Faulty chip/s. Your panel is OK. Easy fix if you can get the components to fix the Bd. Or just buy another working Bd.

Could also be a fault with the main board, as far as a local tech guy who's been fixing TVs for far longer than me told me, despite me disregarding this possibility fairly early on....