Samsung LN46A550P3F - No Power - Clicking

[mrhanso]

Hi,

Firstly, I want to thank all of you for helping me fix my LCD TV a couple of years ago. After replacing the capacitors, it's been running fine ever since. Unfortunately, my other TV isn't as reliable. One day, I went to turn it on and no picture came to the tv. The glowing blue light is on, but no picture ... and a clicking every 26 seconds.

After googling, it appears to be a very common issue with this model, and actually Samsung in general. So I took the TV downstairs to take it apart and most likely replace the capacitors. However, when I look closely at the caps, there is no bulging or leaking at all. I plugged it in without the cover and can see the red light glow on the main board (see picture) and then when the click happens, the light goes out, and then starts to glow again until the next click. I started using the multimeter to test some voltages and everything looked good until I noticed after I took the ribbon cable out of CNI805 connector , I'm getting 0 volts on all of the pins.

Before I arbitrarily replace the caps on a whim, do you think there is another way to see what the issue would be? Any ideas would be helpful!

Thanks,
Mike

[tom66]

Re: Samsung LN46A550P3F - No Power - Clicking

Sounds a lot like a main board fault. Can you acquire some resistors of value around 100 to 470 ohms? These can be used to test the power and inverter boards.

[budm]

Re: Samsung LN46A550P3F - No Power - Clicking

BN44-00202A
http://www.shopjimmy.com/samsung-bn4...wer-supply.htm

Diagram from TOM66 web site.

[mrhanso]

Re: Samsung LN46A550P3F - No Power - Clicking

Thanks for your reply. I have a bunch of spare boards lying around that I can cherry pick. Do any of these resistors look good?. I matched the bands and they seem to be in the range you're looking for. As far as I can read, I have:

Br/Bl/Br/Go = 100?
R/Bl/Br/Go = 200?
Br/Gr/Br/Y = 150?

[tom66]

Re: Samsung LN46A550P3F - No Power - Clicking

The resistors are only used to limit the current going into the pins (so as to avoid damage to the power board), but upon closer inspection, the power board should be fine with direct connection. So, two pieces of wire are necessary. (This board does not have built in pull-up resistor.)

Place one connection between the STB5.1V and PSON, and one connection between STB5.1V and Inverter ON/OFF. Disconnect the main board. You should get a backlight and voltages on the 13V pins.

[mrhanso]

Re: Samsung LN46A550P3F - No Power - Clicking

OK, I just want to be careful here since I've never done this before. Does the picture below look ok? I connected all three ends together.

[tom66]

Re: Samsung LN46A550P3F - No Power - Clicking

The yellow wire needs to go to pin 3, not 2. Otherwise, looks ok to me.

[mrhanso]

Re: Samsung LN46A550P3F - No Power - Clicking

OK, however reading the pins next to the ends of the header, I thought 1&2 were the two in the first row, and 23&24 were the row at the other end. Wouldn't that mean pin 3 is the first in the second row?

[budm]

Re: Samsung LN46A550P3F - No Power - Clicking

It looks right , the bottom row is the odd number pins, the top row is the even number pins.

[tom66]

Re: Samsung LN46A550P3F - No Power - Clicking

Uh, yeah, my error. Sorry.

[mrhanso]

Re: Samsung LN46A550P3F - No Power - Clicking

OK, I did that and the back-light went on. No more clicking, just a steady back-light.

When I tested the voltage on the 13v pins, I got the following:

Pins 19, 21, 22 - 12.72v
Pins 7,8 - 12.88v

I assume this means it's either a mainboard or inverter issue?

[tom66]

Re: Samsung LN46A550P3F - No Power - Clicking

It means it's a main board issue. A common fault with this model.

[mrhanso]

Re: Samsung LN46A550P3F - No Power - Clicking

Is trouble shooting the main board worth it, or is my only hope replacing it?

[munirutech]

Re: Samsung LN46A550P3F - No Power - Clicking

this models have similar faults, mine was that the picture will come correct with sound after 26 to 30 sec it will go off and come again clycle after changing the main board the tv was back working normal

[mrhanso]

Re: Samsung LN46A550P3F - No Power - Clicking

Hope everyone is having a great holiday season. I was finally able to order a replacement main board from shopjimmy.com. After installing it and connecting all of the cables, I plugged in the power cord and crossed my fingers. As soon a I plugged it in, I heard a click and then the tv came on with static and a message saying no signal was detected. I thought I was in the clear until I heard a click and the picture went out. After a couple of seconds, the picture would come on again and then 27 seconds later, click and picture would go out. After three times of this, the clicking would continue every 27 seconds, but the screen would stay black.

At this point, I'm wondering if it even is a main board problem. However, after replacing the new one with the old one again, my old symptoms continued. But, at no point is there ever a picture on the old board. Is it possible it is a power board issue? Are there any other parts of the tv could cause something like this?

Any ideas would be greatly appreciated.

Thanks,
Mike

[tom66]

Re: Samsung LN46A550P3F - No Power - Clicking

Shopjimmy only do basic functional tests of their parts, which are removed from cracked screen TVs. I'd suggest asking for a second main board from Shopjimmy noting your symptoms have improved. You might have to return your original one.

[Don-E]

Re: Samsung LN46A550P3F - No Power - Clicking

I have a model LN46A550P3F with the same problem - no power/clicking. The power supply/backlight inverter board has been replaced and was no help. I think I have identified the eeproms as IC1000 AND IC1003 (ATMLH820 02B1) which are marked in the attached images. I think one may be the backup. The main board is a BN97-02643A and also shows BOT BN41-00975B. I would like to try the eeprom reset but am not sure which would be the correct eeprom and if these are the correct eeproms. I would very much appreciate any help.

[fireman_bob]

Re: Samsung LN46A550P3F - No Power - Clicking

Hi,
Has anyone found the real issue with the main board on these sets? I have one in the shop with the same issue. Replaced the PS caps but still has the cycling problem.
One interesting piece of information is that eventually the set powers on and works fine. If I hold in the power button for 10-15 seconds after the set powers down, I can then press the power button and the set comes up normally, without cycling. This is very repeatable. This leads me to believe there is some issue with the main board, not the power supply.
Any ideas?
Thank you,
Bob

[budm]

Re: Samsung LN46A550P3F - No Power - Clicking

https://www.badcaps.net/forum/showpo...&postcount=129
You can try soldering 100uF 10V low ESR in parallel with C102 on the main board.

[blub]

Re: Samsung LN46A550P3F - No Power - Clicking

Hi,
Has anyone found the real issue with the main board on these sets? I have one in the shop with the same issue. Replaced the PS caps but still has the cycling problem.
One interesting piece of information is that eventually the set powers on and works fine. If I hold in the power button for 10-15 seconds after the set powers down, I can then press the power button and the set comes up normally, without cycling. This is very repeatable. This leads me to believe there is some issue with the main board, not the power supply.
Any ideas?
Thank you,
Bob

Sorry to bump an old thread, but I have an LN37A550P3F with the problem you're describing: power cycling every 30 seconds or so, and if I let it cycle for 10-15 minutes then it stays on and seems to work fine. Did you have any luck bringing yours back to life? Any idea if the motherboard is reparable or just has to be replaced?