My Samsung 48J6400 started behaving strangely: it would take a hard time to turn on (would cycle from on and off a few times before I got it to stay on), until one day it decided not to turn on, just flashed me the power led (blinked twice briefly for 5 times). So I decided to take it to the repair store.
Before I took the TV to the repair shop, I was thinking the problem was work the PSU, since the TV was having a hard time to boot prior to not booting at all. But the diagnosis was that the culprit was the panel, and it would cost a new TV to repair it.
The thing with repair stores here in Brazil is that it is very hard to find a good one, where they really test everything to make sure they find the problem. I just some they run a few tests and if the results are not exactly what they expect, they blame anything. Anyway, I decided to take the TV home and troubleshoot myself.
At the repair store, when they plug the TV to the power, it just turn on, as there was no problem at all with it. Still they insisted that the problem laid on the panel, that the TV could not turn on again later.
When I got home and started troubleshooting, the TV would not turn on again, and would be on a boot loop. So here are my finds during the troubleshoot:
- when I power the TV with all cables off the PSU (a BN44-00709E, BTW, no visible bad cap) but the LED drive, the led backlight stays on, and I assume all of them are lit;
- it doesn't matter if the T-Con is connected of not to the main board, the boot loop is the same;
- sometimes the booting "goes further": the LED backlight turns on, the 3 blue LED indicators on the T-Con board light up, the LED backlight fades out a little, and then it fails: backlight goes off, so does the led indicators at the T-Con board, and the standby red led turns on, further blinking along the T-Con blue LEDs (when one is on, the other is off);
- to end this boot loop, I remove the power from the TV. When I power it back on, the LED backlight would not turn on anymore, no matter how many times I take the power cord out and plug it in;
- after leaving it with no power for a day, I tried to turn the TV on again. It booted without a problem. I even managed to turn it off and on a couple of times, before it went back to the boot loop, without no backlight;
- then I reproduced something I noticed the other night: I discharged the big capacitors by shortening theirs +/- lead (some gave me a pretty loud ZAP along with a flash) to check the back of the PSU, and after verifying that nothing was burned, I connected everything back, and when I powered the TV again, I would get the booting sequence "going further", as in the LED backlight turn on, fades out, and goes off.
In short, that's what I found out:
- if l lay the TV off the power outlet for more then a day, there's quite a big chance that it will turn on;
- once it begins the boot loop if will not stop until the power cord is unplugged. And after that, powering the TV on would just get back to the boot loop;
- if I discharge the big capacitor (I take every ribbon/cable from the PSU before discharging, just to be sure nothing would get damaged by this procedure) and after that connect back the power, the boot "goes further".
To me, it seems that there is(are) some component(s) on the PSU that need(s) to "rest" between boot tries, due to the fact that the TV turns on if laid with no power for 24h+, and would get "further" on the boot sequence if the big capacitors are discharged.
Are my assumptions correct? Is it safe to say that the problem is with the PSU? Would just changing a few components (I was going to change every electrolydic capacitor just to be sure, is there any other components worth checking/changing?) get the problem solved, or it is better to get a new board?
I'll upload the PSU pictures, just hope you can read it.
Before I took the TV to the repair shop, I was thinking the problem was work the PSU, since the TV was having a hard time to boot prior to not booting at all. But the diagnosis was that the culprit was the panel, and it would cost a new TV to repair it.
The thing with repair stores here in Brazil is that it is very hard to find a good one, where they really test everything to make sure they find the problem. I just some they run a few tests and if the results are not exactly what they expect, they blame anything. Anyway, I decided to take the TV home and troubleshoot myself.
At the repair store, when they plug the TV to the power, it just turn on, as there was no problem at all with it. Still they insisted that the problem laid on the panel, that the TV could not turn on again later.
When I got home and started troubleshooting, the TV would not turn on again, and would be on a boot loop. So here are my finds during the troubleshoot:
- when I power the TV with all cables off the PSU (a BN44-00709E, BTW, no visible bad cap) but the LED drive, the led backlight stays on, and I assume all of them are lit;
- it doesn't matter if the T-Con is connected of not to the main board, the boot loop is the same;
- sometimes the booting "goes further": the LED backlight turns on, the 3 blue LED indicators on the T-Con board light up, the LED backlight fades out a little, and then it fails: backlight goes off, so does the led indicators at the T-Con board, and the standby red led turns on, further blinking along the T-Con blue LEDs (when one is on, the other is off);
- to end this boot loop, I remove the power from the TV. When I power it back on, the LED backlight would not turn on anymore, no matter how many times I take the power cord out and plug it in;
- after leaving it with no power for a day, I tried to turn the TV on again. It booted without a problem. I even managed to turn it off and on a couple of times, before it went back to the boot loop, without no backlight;
- then I reproduced something I noticed the other night: I discharged the big capacitors by shortening theirs +/- lead (some gave me a pretty loud ZAP along with a flash) to check the back of the PSU, and after verifying that nothing was burned, I connected everything back, and when I powered the TV again, I would get the booting sequence "going further", as in the LED backlight turn on, fades out, and goes off.
In short, that's what I found out:
- if l lay the TV off the power outlet for more then a day, there's quite a big chance that it will turn on;
- once it begins the boot loop if will not stop until the power cord is unplugged. And after that, powering the TV on would just get back to the boot loop;
- if I discharge the big capacitor (I take every ribbon/cable from the PSU before discharging, just to be sure nothing would get damaged by this procedure) and after that connect back the power, the boot "goes further".
To me, it seems that there is(are) some component(s) on the PSU that need(s) to "rest" between boot tries, due to the fact that the TV turns on if laid with no power for 24h+, and would get "further" on the boot sequence if the big capacitors are discharged.
Are my assumptions correct? Is it safe to say that the problem is with the PSU? Would just changing a few components (I was going to change every electrolydic capacitor just to be sure, is there any other components worth checking/changing?) get the problem solved, or it is better to get a new board?
I'll upload the PSU pictures, just hope you can read it.
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