Samsung PN50C430 no picture-just clicks
 

I am trying to repair a 50 inch Samsung PN50C430 Plasma set, that according to it's owner it started with a blue bar in the center of the picture, then got wider. (I have no idea if it was a horizontal or vertical bar). It's dated in Feb 2010, so it isn't that old. I got the set over here and all it does is click, in about 1 second intervals. No picture, no sound, no light on screen. The clicking is coming from one of the relays on the power supply board. I've tried pulling the power plug from the power supply board at the top right and powered it up, and it still clicks. Unplugged the other cable toward the bottom and it still clicks. If I unplug the cable that runs to the input/remote board, nothing, no clicking. Looked at all the capacitors and I do not see any bulged, and also I do not see any burn't spots, burn't resistors, etc. I am assuming it's either the power supply board, or a short in the Y sustain? board. I am not really an expert on the new flat screen stuff. (Tubes, yokes, and fly-backs are my thing)
Screen looks fine, and is not cracked and I do not see any flaws looking at it closely with a strong flashlight. Any of you guys have an idea where I should start. Thanks.

Update: I went ahead and ordered a good used power supply board from E-bay. Will keep you updated if it works.

I'd be going all over those boards with my ESR meter checking the electrolytics. They can be bad and look good.

I've seen more of these with bad buffer and/or sustain boards than with bad power supplies. Check that buffer board isn't shorted before replacing the sustain board. A shorted buffer board can kill the Y-sustain board.

In your second picture there it looks like there is a heat mark on the Y-sustain board. There will probably be a FET on the other side of the board that has gotten too hot.

I've found and replaced shorted FETs on these before, but more often than not there are other faults. Easier to replace the Y-sustain board with one pulled from another set.

These panels crack very easily. I've cracked a couple myself while handling them (especially frustrating when it happens AFTER you've fixed it).

I never noticed the darkened spot n the Y sustain board. But yes after looking at it more closely, it's there. There cheap on e-bay so I probably will order one along with a buffer board. I'll pull the board and see whats on the other side. It's just too nice of a set to just throw out.

I pulled the Y sustain board and where the darkened spot is there are 3 diodes, (surface mount) 2 appear to be standard diodes, and one Zener diode right behind the spot that looks dark. Problem is the diodes check good with the ohm meter using the diode check function as well. I'm going to hold off and replace the power supply, then if that doesn't work, I'll go for the Y sustain, along with a buffer board. I also checked other transistors, and diodes and couldn't find any bad ones. Although I could very well be missing something. I don't have an ESR meter, just a standard capacitor checker on my meter, and an old capacitor bridge with the green glowing tuning eye tube. In order for me to check them I would have to pull the caps first. Too risky to do that with these intricate circuit boards.

I wouldn't bother checking the caps if you don't already have an ESR meter. The ESR can be unacceptable while they still measure spot on for capacitance. Before I got one I'd just replace any that looked suspicious (bulging, oozing) or were connected to anything else that looked suspicious (across the diodes that got hot).

Do all the supply rails come up? A bad sustain board can shut down the power supply. If Vs doesn't come up with the sustain board connected, but does come up with it disconnected the power supply is probably good. The main board will still shut it down when the set doesn't start up correctly.

If Vs (or VA) doesn't come up at all look for dry joints before replacing the board. I've fixed many Samsung plasma power supplies resoldering the FETs, driver transformers, diodes.

Disconnect the buffer board from the sustain board and power the set up. Check if Vscan (generated from Vs by a DC-DC converter on the sustain board) comes up.

Check the buffer board between Vscan and gnd with your meter on diode check. If it's not shorted it's probably ok. They can fail without shorting, but at least then they don't take out the sustain board.

If buffer board is shorted you can cut the Vscan traces to the buffer ICs to find and isolate the bad ones. Usually 1 or 2 will short, but the others are ok. With the shorted buffer ICs disconnected you can put it back in and you should get a partial picture if everything else is ok. The areas of the screen associated with the disconnected ICs should be completely dark.

If you see the blue line they mentioned at this point you've got a bad panel.

If buffer ICs that were ok immediately short you've got a short in the panel itself.

First off I have 0 voltage at both the VS and VA test points, not even for an instant when plugged in. Remote or power buttons do nothing. I unplugged the Y sustain board, from the power supply plugged the set in, still nothing, no voltages (not even for a moment), just clicks. I removed the power connector from the power supply that goes to the main board, no clicks, no voltage, nothing. I have yet to try connecting the Y sustain board to the power supply with the buffer board disconnected, There are no bulging capacitors anywhere that I can see. I do have voltage though on the hot side (AC line cord side) of the power supply, at the 2 big capacitors at the top left of the board. The voltage there jumps up and down as it clicks bouncing around 450 volts DC. I will look over the power supply board closer for bad connections, but I do have a replacement coming. I will try the Y sustain hooked up to the power supply with the buffer board disconnected. I doubt it will change anything but will give it a try. Right now I feel I have a 50/50 chance of the power supply board being bad. Time will tell.

Often on these PS boards...if the main run voltages fall to 0 (the VS and VA lines) the power WILL just "click on and off continuously". No VS or VA supply means that one of the SMPS ckts is not working--either due to a bad load on the clod side--or not running on the primary side.

Have you checked to see if the FET'S that drive that upper transformer are not shorted...and a fuse or resistor feeding them open? If not...perhaps a diode on the secondary of those supplies is shorted.

often...there are "kits" on ebay or shop jimmy--with the parts that fail on these PS baords... they work good for someone who is not used to troubleshooting down to the "nitty gritty".. FInd the boars and order by that... looks like BN44-00274A


THIS..likely will fix your PS board::

http://www.ebay.com/itm/Samsung-BN44...4AAOSw-7RVHtP-

Thanks for the info. I do have a supposedly good used board coming from e-bay so will give that a try, but I will also check more connections diodes and FET's etc as well.

If you are going to service SS gear an ESR tester is essential. There are ESR testers on ebay for ~$15 that have the additional features of RLC component testing and transistor/diode testing....I have one and consider it one of the best pieces of cheap test equipment I've got.

Agree, but what do you use for probes? I just got a tweezer probe that is not up to the task on low esr smt caps... hate to have to spend more on probes than the meter cost. :no:

jr

I "probed" around on ebay and found some long (maybe 2") needle-pointed probes that attach with banana plugs, and I added some shrink wrap. Been years though. You might find something similar.

http://www.videokarma.org/attachment...4&d=1339600483

I've never used it on SMD caps (never needed to test those), so I just soldered some solid core wire (which the stock connector on my meter grabs) to some alligator clips. If I need sharp point probes I just put some lead stubs in the alligator clips.

Disconnected the buffer board and left the Y sustain and others powered up to the power supply. Still just clicking relay. So I just got a power supply replacement board in the mail from E-bay yesterday. Guess what: it was damaged in shipment with the box crushed and a corner of the board broken off. Can't use, so now have to go a find another one and get a credit.
This is the first time I've had any package damaged by USPS. Oh well things happen.