Samsung LN55C630K1F power failure (BN44-00342B power board)

[matomato13]

Hi everyone,

A friend of mine gave me his TV after it stopped working, he gave up trying to fix it after it caused him so much trouble throughout the years (flickering image, sometimes no backlight, etc.). The latest problem was a weird noise and no power.

I opened the TV and saw the power supply board with a transformer burnt. Here's the pictures.







Notice the green component has slightly darker color on the board, could it be an issue with that also? Would it be safe to replace the transformer? Anything to look for that might have caused this and that should also be replaced?

Thank you

FYI: for the previous problems, I replaced 2 backlight inverters
http://www.tvparts.ca/tvdetail.php?id=381
http://www.tvparts.ca/tvdetail.php?id=382

I also cut the jumper JP854 like in this video https://www.youtube.com/watch?v=i-jQZ-TQdgU

It never fixed the issue.

[budm]

Re: Samsung LN55C630K1F power failure (BN44-00342B power board)

I would replace both of those inverter transformer at the same time, it got hot and discolored the PCB. You also need to check the inverter transformer drive circuit to see if anything else are damaged or not when that transformer failed.
Cutting the jumper is NOT a fix, all it did is bypassing the PROTECTION circuit. The PFC Boosted Voltage is low that is why the backlights were flashing, if you check the DCV between the two legs of the main filter cap, it will probably show about 360VDC in stead of 380~400VDC.
Someone should tell that guy on YOUTUBE of what he actually did, bypassing PROTECTION CIRCUIT!

[CapLeaker]

Re: Samsung LN55C630K1F power failure (BN44-00342B power board)

If you remove the protection circuit for the backlights, I would only recommend that for testing purposes, nothing else. There is a reason for a protection circuit. Disabling it isn't such a bright idea in order to "fix" the TV.

[matomato13]

Re: Samsung LN55C630K1F power failure (BN44-00342B power board)

OK, I'll resolder the jumper.

Any idea how I can get any technical specs for a replacement transformer? I tried searching for what's written on it but I didn't find anything.

[matomato13]

Re: Samsung LN55C630K1F power failure (BN44-00342B power board)

I guess at this point I should probably replace the board completely, it will fix the power and flicker issue, right?

[CapLeaker]

Re: Samsung LN55C630K1F power failure (BN44-00342B power board)

Take the transformer off the board. Who knows what it is going to look like underneath of it. Also that transformer is obviously toast, so you could find a bad PSU and swap out the transformer, find a replacement transformer online somewhere, or buy a new PSU altogether. Another option is to fix that transformer and take it apart.

[matomato13]

Re: Samsung LN55C630K1F power failure (BN44-00342B power board)

Here's the board and underside of the transfo





I tried searching for a replacement part but nothing comes up and I have no specifications on what's needed.

[matomato13]

Re: Samsung LN55C630K1F power failure (BN44-00342B power board)

OK so I replaced the power board completely and now the TV turns on. But there's no backlight.

Here's the startup:
1) Red light blinks
2) Samsung power on music plays
3) Backlight turns on before picture then turns off
4) TV is on but no backlight, I can see the image with a flashlight.

A few years ago I replaced the two backlight inverter boards, I thought it might fix a backlight turning off after watching TV for a few hours problem, but it didn't, so the boards should be fine I think. I just replaced them and I have the exact same behavior, no backlight.

Where should I look for now?

After doing a bit of research I've found an old thread where budm you mention something about protection mode because of a lamp problem (https://www.badcaps.net/forum/showthread.php?t=25316) Could this be it and can something be done?

[CapLeaker]

Re: Samsung LN55C630K1F power failure (BN44-00342B power board)

If it is indeed a ccfl problem. No, they are worn out then. But you surely could fix a bad connection somewhere. The other possibility is that you got another bad PSU. Try comparing the high voltage windings on the transformers with your ohm meter.

I am not in favour for disabling the protection circuit and leave it off, like some do.

[budm]

Re: Samsung LN55C630K1F power failure (BN44-00342B power board)

Did you see the backlights even flash on for seconds?
If you have bad lamp/s when the inverter at first start up it will supply the firing Voltage in an attempt to light up the lamps first since it does not know if you have bad lamps or not, then if ALL the lamps did not conduct THEN the protection will kick in. So you should at least see the backlights flash on from the good lamps if the inverter circuits are good, and then the backlights circuit will shutdown if it has some bad lamps.

[matomato13]

Re: Samsung LN55C630K1F power failure (BN44-00342B power board)

Yes I saw the backlight for a few seconds (2 maybe)

[CapLeaker]

Re: Samsung LN55C630K1F power failure (BN44-00342B power board)

chance is good that one of the inverter transformers is bad, or one of the CCFLs is bad or a bad connection in the wiring.

[matomato13]

Re: Samsung LN55C630K1F power failure (BN44-00342B power board)

I tested the transformers and they are good. I'd like to do a test like this to find out which CCFL (or it's connection) might be causing the issue but I'm not sure which pin I should take the measure on.

https://www.youtube.com/watch?v=oE6K4xBVweA

Here's the inverter boards I have
http://www.shopjimmy.com/auo-19-54t0...t-inverter.htm
http://www.shopjimmy.com/auo-19-54t0...t-inverter.htm

[budm]

Re: Samsung LN55C630K1F power failure (BN44-00342B power board)

We need to verify that your new board is OK or not first.
1) You need to verify that you do have 380VDC or more between the two legs of the main filter cap when TV is on.

2) You need to check the DCV (when TV is turned on) the connector CNI802 of the power supply-inverter board combo pin 1 for 12VDC, and >10VDC on pin 7 (LD-Lamp Detect), if one or more lamps are bad the LD pin will be <6VDC.

3) If the lamp/s are bad then you can check the ACV (set meter to 20VAC range or less, your meter also need to have high frequency AC bandwidth. Chassis as GND ref) on those 10 test points I mark on the Master Balancer board (it is Balancer board not inverter board as described by SJ). You have to leave the meter on the test point and turn on the TV each time to catch ACV reading as shown in the video, you will have to do that 10 times to see which one shows much higher ACV than the rest.

[CapLeaker]

Re: Samsung LN55C630K1F power failure (BN44-00342B power board)

Plus you can check the resistance of the secondary (output) winding on east transformer on the inverter board. If one reads 3% off, its bad.

[matomato13]

Re: Samsung LN55C630K1F power failure (BN44-00342B power board)

OK so everything was good for 1 and 2.

For test #3, here's the voltage measured (I also checked the other board).

1 18v
2 15v
3 11.8v
4 6.8v
5 2.4v
6 5.7v
7 1.6v
8 2.2v
9 1.6v
10 18v
11 16.7v
12 15.6v
13 18v
14 15v
15 16.7v
16 17v
17 16.2v
18 17.8v

Values seem very weird though...

[matomato13]

Re: Samsung LN55C630K1F power failure (BN44-00342B power board)

Oops didn't mean to post this...

[budm]

Re: Samsung LN55C630K1F power failure (BN44-00342B power board)

OK so everything was good for 1 and 2.

For test #3, here's the voltage measured (I also checked the other board).

1 18v
2 15v
3 11.8v
4 6.8v
5 2.4v
6 5.7v
7 1.6v
8 2.2v
9 1.6v
10 18v
11 16.7v
12 15.6v
13 18v
14 15v
15 16.7v
16 17v
17 16.2v
18 17.8v

Values seem very weird though...

I have no idea what the 1~18 are about.

[matomato13]

Re: Samsung LN55C630K1F power failure (BN44-00342B power board)

I have no idea what the 1~18 are about.

Yeah sorry about that formatting.

The last board you asked to take ACV readings.

1~10 = the points you highlighted
11~18 = same points on other board below it.

[budm]

Re: Samsung LN55C630K1F power failure (BN44-00342B power board)

https://www.youtube.com/watch?v=oE6K4xBVweA

Video @2:11, 3:10, 6:00

Those Voltage you are seeing are very HIGH, per Video, the one with bad lamp the ACV is around 1.5VAC.
But since they are not the exact same board but still the same topology being used, I expect to see may be one or two readings that are way off from the rest but yours has so many readings that are way off from others.
BTW, how about the DCV reading of the 12V and the LD pin?