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

[matomato13]

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

I have 12.12V on the Pin 1 (12V) and 8.74V on Pin 7 (LD)

For the main filter caps
386V on CP802
367V on CP803

I also got a new multimeter, here's the readings for ACV on the 18 test points

1 2.6
2 2.0
3 1.4
4 0.9
5 0.4
6 0.7
7 0.5
8 0.4
9 0.6
10 3.4
11 4.7
12 3.3
13 4.3
14 4.3
15 2.5
16 2.5
17 2.2
18 3.3

[budm]

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

'For the main filter caps
386V on CP802
367V on CP803'

That cannot be right since both caps are connected in parallel so the Voltage should be the same, as if the Voltage is at 367 VDC that can be the problem.

[matomato13]

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

What should I do in this case?

[budm]

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

Take the reading aging so we know the exact Voltage on the caps. It does not help if we have wrong data due to improper measurement.

[matomato13]

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

OK so I measured again and the voltage onthe caps is 368-369V on both, maybe I took some time between the 2 measurements last time (ie startup and later?)

[matomato13]

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

Is the voltage being low the cause or the effect of the backlight problem? Wht should I test next?

[CapLeaker]

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

I have 12.12V on the Pin 1 (12V) and 8.74V on Pin 7 (LD)

For the main filter caps
386V on CP802
367V on CP803

I also got a new multimeter, here's the readings for ACV on the 18 test points

1 2.6
2 2.0
3 1.4
4 0.9
5 0.4
6 0.7
7 0.5
8 0.4
9 0.6
10 3.4
11 4.7
12 3.3
13 4.3
14 4.3
15 2.5
16 2.5
17 2.2
18 3.3

These test points you are talking about don't mean nothing when we don't know the pin out name that go with it. Second, these voltages need to be measured in DC V.

[matomato13]

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

These test points you are talking about don't mean nothing when we don't know the pin out name that go with it. Second, these voltages need to be measured in DC V.

Well I was told to get the AC V on the pins in red (see https://www.badcaps.net/forum/attach...4&d=1475896228)

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?

[CapLeaker]

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

Ok, sorry... got it, didn't read the whole thing. Yes, those points have to be measured in AC mode. I thought you were measuring a pin out on a connector or something.

[matomato13]

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

Ok, sorry... got it, didn't read the whole thing. Yes, those points have to be measured in AC mode. I thought you were measuring a pin out on a connector or something.

No problem . By the way, on my last post about low voltage I was referring to the main filter cap voltage.

[CapLeaker]

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

The filter cap voltage is good, the PFC is up and running. This TV has 2 inverter boards. So I think there is trouble with one of them. The backlight control ic must be working, as you getting a flash of backlight when you turn the TV on.
Recheck the resistance of the output winding of each inverter transformer on both inverter boards. Also go with your DMM in diode mode over each diode on both inverter boards.

[matomato13]

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

yes I'm getting a flash.

what do you mean by check resistance of output winding of the transformers?

[matomato13]

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

I tried with 2 other inverter boards that were on this TV before (changed them but didn't fix the issue at the time) and now I'm getting the image for a few second (showing TV 3 with "snow") and then the backlight stops, image is still there (checked with a flashlight).

I'm wondering if the inverter boards have some sort of ground with the screws since I just connected it without screwing anything.

[matomato13]

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

So last night, I was running the inverter boards connected but not screwed to the TV, just hanging by the connectors and I was able to see the image, maybe the backlight was staying on longer.

Now I put the 4 screws that have a metal plate around the holes and I get the same thing as before, a flash for a second and then black.

[CapLeaker]

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

this inverter board uses 2 transformers per CCFL (keep that in mind). Unplug everything from it. Next to the CCFL connectors is a test point on each side. That is the secondary output side of the transformers. Check these TPs as a pair. Set you DMM to Ohm, put one lead to one TP on one side of the CCFL connector and do the same with the other lead of you DMM to the other side, read write down the resistance (Ohms) you measured. After you have done this to all CCFL TP's or on the connector, look at the measurements and see if something sticks out. All these measurements have to be within 3% of each other.
If you did identify a bad transformer (you can measure each transformer individually to on pin 5 and 6 and compare all of them), then you need a new inverter or a new replacement transformer.

[matomato13]

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

OK, I haven'5 had the time to check but I've noticed something weird. I opened the TV and the input was previously TV and since it's not connected to anything, I was getting snow and as soon as the snow appeared the backlight would close. I changed the input to HDMI 1 and restarted the TV. Since there's no snow on this input, the TV stayed opened for a long time. As soon as I changed the input to TV, the backlight closed.

[matomato13]

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

There's also a buzzing noise coming from the second transformer starting from the top on the bottom inverter board when the backlight is on. Lowering the backlight in the menu diminishes the buzzing noise.

[matomato13]

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

I replaced the bottom board that was buzzing and no more buzzing noise, but still the same problem if I switch to TV input and get the snow it closes almost inmediately.

I left the TV on for about 5-10min on the HDMI input (with nothing connected) and it stayed opened. I changed the input to TV and it stayed on this time... I'm really lost here..