Samsung PN43E450A1F Troubleshooting

[LT630]

Yesterday, my TV was on. I was not watching it and had my back turned when I heard a loud POP. I turned around and my TV was off and would not turn back on again with the remote or the power button. I first checked my surge protector and cords, and I did not find any problems. All of my other components worked fine. Also, the standby light on the TV blinks intermittently. So, I know it is getting some power.

I next took the back off the TV. I hoped I would be able to find a blown capacitor or something visually the problem, but everything internally looks fine. Following this visual inspection, I unplugged all the boards except the power supply board and the main board. This seemed to make no difference, and since the problem is not with the picture, I assume the X and Y boards are not the problem.

I strongly suspected my power supply board was to blame, but I got my multimeter and checked around a bit. The power supply board is sending 5.23V of standby power to the main board. So, I now suspect it is the problem. I am considering ordering a replacement board, but just wanted to check and see if anyone had any advice, or if there is any more troubleshooting I can do to make sure that this is definitely the problem. For instance, I am not sure how to test whether the problem is the main board or the logic board. They are connected with a ribbon cable, and I don't know if it would make any difference to disconnect this or not. I am also not sure what else I can test. I would appreciate any insight. I am a poor grad student and can't afford a new TV, or even a TV repair bill.

Thanks!

[tw2005]

Re: Samsung PN43E450A1F Troubleshooting

Yesterday, my TV was on. I was not watching it and had my back turned when I heard a loud POP. I turned around and my TV was off and would not turn back on again with the remote or the power button. I first checked my surge protector and cords, and I did not find any problems. All of my other components worked fine. Also, the standby light on the TV blinks intermittently. So, I know it is getting some power.

I next took the back off the TV. I hoped I would be able to find a blown capacitor or something visually the problem, but everything internally looks fine. Following this visual inspection, I unplugged all the boards except the power supply board and the main board. This seemed to make no difference, and since the problem is not with the picture, I assume the X and Y boards are not the problem.

I strongly suspected my power supply board was to blame, but I got my multimeter and checked around a bit. The power supply board is sending 5.23V of standby power to the main board. So, I now suspect it is the problem. I am considering ordering a replacement board, but just wanted to check and see if anyone had any advice, or if there is any more troubleshooting I can do to make sure that this is definitely the problem. For instance, I am not sure how to test whether the problem is the main board or the logic board. They are connected with a ribbon cable, and I don't know if it would make any difference to disconnect this or not. I am also not sure what else I can test. I would appreciate any insight. I am a poor grad student and can't afford a new TV, or even a TV repair bill.

Thanks!

I would wait until you get someone who's possibly worked on these but Ymain, Y buffers and xmain would be first on my list of suspects.

If you want to measure things, check the y and x boards for shorted out transistors on the heatsinks (locations start with "Q") obviously wiyth no power running.

Also there's normally a small logic board with a green LED that blinks. If it's doing a slow blink like once / 5 secs then it's in protection which would also suggest the sustain boards.

depending on the version or board numbers in this they appear to be fairly cheap on Shopjimmy.

try a search on pn43e450 or some of the board numbers as you may find other related posts.

[Hamie]

Re: Samsung PN43E450A1F Troubleshooting

Check what voltage you get on SVT_VSCAN test point on the y-sustain.

The voltage will only appear briefly when turning the set on then drop back to 0.

In the UK this TV is PS43e450.

[Alastair E]

Re: Samsung PN43E450A1F Troubleshooting

E series kill the X-SUS as I recall--like the earlier D series....

Best to replace both the Y and the X at the same time--as one can kill the other....

[LT630]

Re: Samsung PN43E450A1F Troubleshooting

I unplugged everything from the main and power supply boards and the tv still won't power on at all. Wouldn't this rule out all the x and y boards as being the problem? Also, I've seen the green light on the logic board, but it doesn't stay on or blink rhythmically.

[dick_barton]

Re: Samsung PN43E450A1F Troubleshooting

Disconnect the supplies to the X and Y boards and see if the voltatges come up on the power supply.
You can also check the resistance (set off) between VA, VSC, VE etc to ground and see if there's a short. Also if any of the fuses have blown on any of the boards.

[tw2005]

Re: Samsung PN43E450A1F Troubleshooting

I unplugged everything from the main and power supply boards and the tv still won't power on at all. Wouldn't this rule out all the x and y boards as being the problem? Also, I've seen the green light on the logic board, but it doesn't stay on or blink rhythmically.

No not really as part of the shutdown circuit is designed to detect disconnection which is why it is being suggested to measure as you power on with those boards disconnected as you should briefly see voltage.

[LT630]

Re: Samsung PN43E450A1F Troubleshooting

Thanks for all the help. So, I checked the VS and the VA voltages at the test points with all the boards plugged in. When I do this, VS spikes my meter to OL and then dies back to zero. I next unplugged the X and Y boards from the Power supply and tested VS and VA again. Va read -2.5mV and stayed constant. Vs is supposed to be 209V. When I put power to the TV, the voltage on this test point was low, but kept climbing steadily. It would go up, and then go down a few volts, and then go higher than before. After a minute or two of the TV being plugged in, the voltage on this test point was over 400 and I got freaked out and unplugged everything. What does this mean?

[LT630]

Re: Samsung PN43E450A1F Troubleshooting

Clarification of my previous post. When only the Power supply and main boards were plugged in, the voltage on Vs steadily climbed to 400mV before I unplugged it. I checked this again today, however, and it did something different. This time the voltage at Vs quickly spiked to 400mV and then slowly discharged back down to almost zero. When all boards are connected the voltage at Vs and Va spike to OL when I first give power to the tv and then fall back down. This seems like the problem is with the power supply board to me. What can I check to confirm this?

[tw2005]

Re: Samsung PN43E450A1F Troubleshooting

Clarification of my previous post. When only the Power supply and main boards were plugged in, the voltage on Vs steadily climbed to 400mV before I unplugged it. I checked this again today, however, and it did something different. This time the voltage at Vs quickly spiked to 400mV and then slowly discharged back down to almost zero. When all boards are connected the voltage at Vs and Va spike to OL when I first give power to the tv and then fall back down. This seems like the problem is with the power supply board to me. What can I check to confirm this?

when the meter went to OL, what was it set to? Something over 200Vdc?

Sounds as though unless the other boards are connected it detects those missing and no power. Would suggest it's not the power board and as soon as power is supplied it shuts down due to a fault on the boards connected to it.

I'd be checking the x and y boards for shorts or low resistance on the Vs lines

[LT630]

Re: Samsung PN43E450A1F Troubleshooting

Thanks for the reply TW. My meter is autoranging with a max of 600V. So, OL should mean well higher than what it is supposed to be, which is 209V.

Could you please talk me through how to check for shorts and resistance on the Vs lines? If its not the Power board, my next suspicion would be the X/Y main board.

[Alastair E]

Re: Samsung PN43E450A1F Troubleshooting

Very slow Auto-Ranging meters do that. (They are ALL Slow IMHO) One reason I Hate the bloody things!

Can you not set the meter into Not Auto Range mode, say 250-300V range?

[dick_barton]

Re: Samsung PN43E450A1F Troubleshooting

With everything connected but the set OFF using your meter set to ohms measure the resistance at the various voltage test points, Vs, VE, Va etc. to chassis.

[LT630]

Re: Samsung PN43E450A1F Troubleshooting

Thanks, Dick. The resistances I got doing what you suggested are as follows.

Vs - moved around a bit the few times I would check it, but stayed around 1-2Ω
Va - always 17.46 kΩ
SVT_Vscan on the X/Y Main - Would start OL then fall gradually to around 100 kΩ
SVT_XOut on the X Buffer - Would start OL then fall gradually to around 100 kΩ
SVT_VS on the X Buffer - 1-2Ω
SVT_VS on the X/Y Main - 1-2Ω
SVT_VE on the X/Y Main - Would start OL then fall gradually to around 100 kΩ

[dick_barton]

Re: Samsung PN43E450A1F Troubleshooting

Thanks, Dick. The resistances I got doing what you suggested are as follows.

Vs - moved around a bit the few times I would check it, but stayed around 1-2Ω
Va - always 17.46 kΩ
SVT_Vscan on the X/Y Main - Would start OL then fall gradually to around 100 kΩ
SVT_XOut on the X Buffer - Would start OL then fall gradually to around 100 kΩ
SVT_VS on the X Buffer - 1-2Ω
SVT_VS on the X/Y Main - 1-2Ω
SVT_VE on the X/Y Main - Would start OL then fall gradually to around 100 kΩ

You have a short circuit on the Vs line so you need to find where the short circuit is. Disconnect the supplies from all the boards and see which board(s) gives 1-2 ohm resistance at Vs & SVT_VS.

Edit:
I'm not familiar with Plasma but I assume that SVT_VS is derived from VS.

[dick_barton]

Re: Samsung PN43E450A1F Troubleshooting

If you could post some nice sharp pictures of the boards would prove useful.

[LT630]

Re: Samsung PN43E450A1F Troubleshooting

Okay, here are some pictures of the different boards. I also disconnected all the boards and tested the resistances in isolation. When I did this, the only test point that showed a 1-2 ohm resistance was SVT_VS on the X/Y main board (0784). This seems to isolate the problem to this board, correct?

Do you guys think it would be okay to replace this whole board with one from ShopJimmy, or would I need to replace the X and Y buffers too? Alternatively, would there be any way to isolate exactly which component on this board failed? If it's just a capacitor or two, I would prefer to replace just those.

Thanks again everyone for all the help!

[chrismurphy]

Re: Samsung PN43E450A1F Troubleshooting

error

[dick_barton]

Re: Samsung PN43E450A1F Troubleshooting

Using your meter can you test the mosfets by placing your probes on the legs of each of the mosfets and also do the same for the diodes and see which components are short circuit.

Chances are that some of your mosfets/diodes are blown on that board.

A sharper picture of the board top and bottom could help.

There are Youtube videos showing how to test the devices using your meter.