View Full Version : Samsung PN50C430 no picture-just clicks


walterbeers
04-16-2016, 05:28 PM
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.

walterbeers
04-17-2016, 06:20 PM
Update: I went ahead and ordered a good used power supply board from E-bay. Will keep you updated if it works.

Ed in Tx
04-17-2016, 08:14 PM
I'd be going all over those boards with my ESR meter checking the electrolytics. They can be bad and look good.

dr.ido
04-17-2016, 08:28 PM
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).

walterbeers
04-18-2016, 06:41 AM
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.

walterbeers
04-18-2016, 01:59 PM
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 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.

dr.ido
04-18-2016, 08:54 PM
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.

walterbeers
04-18-2016, 09:55 PM
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.

rca2000
04-18-2016, 10:13 PM
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-BN44-00274A-Power-Supply-Component-Repair-Kit-/361421733132?hash=item542669fd0c:g:9l4AAOSw-7RVHtP-

walterbeers
04-19-2016, 06:13 AM
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.

Electronic M
04-19-2016, 12:19 PM
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.

jr_tech
04-21-2016, 07:09 PM
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

Ed in Tx
04-21-2016, 07:17 PM
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.php?attachmentid=174914&d=1339600483

Electronic M
04-22-2016, 01:34 AM
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'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.

walterbeers
04-22-2016, 06:05 AM
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.

Ed in Tx
04-22-2016, 08:25 AM
I've never used it on SMD caps (never needed to test those)... That's amazing, considering all the failures of SMD caps I've seen. Sony camcorders were some of the worst, 20 years ago. Many different devices come to mind... JVC hi-fi audio boards (no or distorted audio), Panasonic VCRs, just about any model including the AG "Pro line" models, I have a mint condition AG-1830 here with so many SMD caps bad it's hopeless. Used in so many electronic devices. I have a Icom 706 Mk IIG here with bad SMD caps all over. A $1000 radio.:tears:

Electronic M
04-22-2016, 12:16 PM
Well I don't do it for a living...The SS gear I fix is mine and mostly 70's-90's stuff. I can't do SMD soldering worth a crap (nor do I see value in buying gear to do it better) so most stuff where the issue is most likely SMD gets round filed when it dies...Generally speaking most post 1980 SS stuff here gets the round file when it dies...Only things that have performed very well, have special features I like, or would be too costly to replace merit bench time upon failure.

walterbeers
04-25-2016, 10:20 AM
Generally I've had no or very little luck soldering surface mount devices. Generally I just try to replace the board. Most of this newer stuff seems that either you change the board or trash the unit. Of course with cheap foreign made junk, generally you use it for a few years, it quits, and then you junk it for a newer "more improved" model. Just look at the cell phone industry. Most phones are only kept for 2 or 3 years (if that) and trashed for a newer model. Although I have a cell phone, our landline gets more use than my cell. Plus a landline is dependable, no dead spots, poor or dropped connections. Well so much about that. As far as the Samsung 50 inch, I ordered another power supply board, and should get it this week. I just hope they don't break this one in shipment. I'm still taking a chance that this will fix it.

walterbeers
04-28-2016, 03:48 PM
Well, I got the replacement power supply board, installed it and it powered up. Picture is great, but not quite as it should be though. I have full screen, good color, no missing areas on the screen or solid lines, etc. But at times there are small digital sparkles, (sort of like snow you would see on a weak analog channel but finer) and it sort of looks like very fine (analog looking) horizontal trace lines like you would see on a low def. CRT set. Picture is bright, crisp looking, otherwise normal. One time (and only once) I tapped the Y sustain board and the sparkles disappeared, but came back once the set cooled off and I turned it on again. I am just receiving local high def channels over the air as of now. It's hard right now for me to take a photo screen shot as it had been wall mounted and I do not have a base here for it, so I have it leaning up against a wall with cardboard boxes bracing it so it doesn't slide over or break. I am suspecting the Y sustain board, as it is producing a low audible buzz noise. I ordered a replacement Y sustain, and I'm hoping that will take care of the problem. Here are some pictures of some parts of the screen taken at close range. Any thoughts? I hope I'm on the right track. All heat sinks run quite warm to the touch, but I assume that is normal.

andy
04-29-2016, 01:37 AM
Have you adjusted the new power supply to match the voltages printed on the panel? Each panel is different, and slightly incorrect voltages will cause random light, or dark dots.

walterbeers
04-30-2016, 05:08 PM
Yes, I checked the power supply voltages and they are exactly right on. I just received the new Y sustain board and installed it. Still a few sparkles but almost gone. Of course this is on broadcast stations. I hooked up a blue-ray player and pictures looks perfect no sparkles at all. Also with the replacement board (y sustain) the lines don't pair up anymore, looks pretty good. I think I will put it back together and see how it goes.

walterbeers
05-01-2016, 06:14 PM
The sparkles are there for the first 10 minutes or so, then they disappear. I've tried adjusting the 3 pots on the Y sustain and it just seems to make it worse to I moved them back to the original position. Maybe it's the buffer board, but seems as if the only one available right now on E-bay is $80, and it might not even take care of the problem. I think my friend who I'm fixing it for is just going to have to live with it. It is possible there is some damage to the screen? It was hauled horizontally in a pickup with the glass facing down.

CoogarXR
05-02-2016, 08:34 AM
I know on some models, specifically the Vizio 42s with the LG panel (VP42, P42HD, etc), I would see sparkles on the high-hour sets. I would tweak them out with the pots as best as I could, but they didn't always go away completely.

I guess I am saying, with your set, it might have a lot of hours on it, and that's as good as it's going to get.

Also, that laying-flat thing is an old wives tale in my opinion. When I worked at the recycler, ALL of our TVs were shipped to us flat, in stacks, on pallets. You've seen how they work, I don't see how anything could be damaged by laying them down.

andy
05-02-2016, 10:22 AM
Speckles is a common symptom of a weak plasma panel. I've only seen it on Korean panels (LG and Samsung). They can usually be reduced with careful adjustment, and usually get better as the set warms up.

walterbeers
05-12-2016, 10:17 PM
The set was quite a challenge to fix, but I now have it working really good, once it warms up for 5 or 10 minutes. Apparently the set has had quite a few hours on it and being a Samsung, I believe the sparkles are just caused by a weak high hours panel. But fixing it became quite a challenge. First finding out the power supply was the main culprit, and I ordered a used one off E-bay. Well that one came in the mail with the box crushed and one corner of the panel broken off, so had to send it back for credit and order another one from a different supplier. Then after seeing pairing of lines and sparkles, I figured out the Y sustain board had problems. I ordered one (also of E-bay), adjusted the pots on the board for the least amount of sparkles and had a good picture, well for about 2 hours, and guess what, I went back to check on the set, and the screen was flashing off and on, high contrast, super bright. Checked power supply voltages, and they were jumping up and down. Unplugged the Y sustain, and power supply voltages were normal, and adjustable, but no picture of course. Well scrap the Y sustain board, and ordered another. Got the 2nd Y sustain board in the set (adjusted the pots) and the set has worked perfect for over a week now, about 6-8 hours a day. Apparently the first Y sustain board crapped out after a couple of hours of use. Finally got everything back together and the set is looking good, except for a few sparkles when first turned on. Another "learning" project completed. I think working on old tube TVs is actually easier to troubleshoot.

Eric H
05-13-2016, 12:54 AM
You might be able to check the actual hours on this set by using one of the methods listed here:

http://www.hometheatershack.com/forums/hdtv-video-displays-processors/23475-how-check-hours-used-your-plasma.html

walterbeers
08-28-2016, 08:36 AM
I just found out yesterday my repairs were a success, after the replacement of both the power supply board and the Y sustain board. My friend that owns the set says it's still going strong, yes a few sparkles in the picture most likely due to a weak plasma panel, but I was able to reduce them to a minimum with adjustments on the Y sustain. It has an excellent picture otherwise and they are happy with the results. Thanks for all the advice from fellow VKers.

Titan1a
08-28-2016, 06:48 PM
Good show!