BN44-00301A No signs of life

[snoptel]

Hi everyone.
I have a Samsung TV with a BN44-00301A PS board. When plugged in the TV shows no signs of life what so ever. No red standby light, no clicking, no back light..nothing!!

First, I can´t find the right schematic online, if anyone has a copy, or know where I can get one I would really appreciate it.

Second, I have checked the fuses, they are good. I have measured +/- 400VDC at the rectifier bridge.

I'm a noob at this so any help would be awesome.

Pics of the board are attached..no signs of heat of anything else.
Cheers.

[madan1]

Re: BN44-00301A No signs of life

Start measuring this connector. There is a pinout right next to it.

[snoptel]

Re: BN44-00301A No signs of life

Start measuring this connector. There is a pinout right next to it.

Thanks for the reply. I did, no voltages at all..

[snoptel]

Re: BN44-00301A No signs of life

From what I've been reading, 5,1VDC should be available when the TV is off. I don't have that voltage anywhere.

Anyone know where the jumper must be placed in order for the inverter to switch on when outside of the TV?

[stj]

Re: BN44-00301A No signs of life

the small cap near the center of the board starts the buck convertor chip to it's right on the heatsink, that generates your 5v standby.
i assume you pulled the fuses out and metered them?
you pull them out so you know that the clips are tight - just so you know.

[harp]

Re: BN44-00301A No signs of life

Have you familiar with diode mode on dmm?
When is tv not connected to main and in big caps is no voltage:
with multimetar in diode mode check briefly all transistor and diodes... you are looking to find possible short 0.000 on them.
All must have some readings in one direction of probes, like 0.678...

[R_J]

Re: BN44-00301A No signs of life

All you need to do is check if you have 5 volts standby, if you do not have 5v stby then check fuse FS802 if it is bad then icm801 is lkely bad.

Check if the small blue disc cap next to the ic is cracked or has a burn mark. sometimes this cap shorts.

[snoptel]

Re: BN44-00301A No signs of life

Have you familiar with diode mode on dmm?
When is tv not connected to main and in big caps is no voltage:
with multimetar in diode mode check briefly all transistor and diodes... you are looking to find possible short 0.000 on them.
All must have some readings in one direction of probes, like 0.678...

Yes, I actually had already probed all the diodes and transistors and didn't find anything that caught my attention.

[snoptel]

Re: BN44-00301A No signs of life

All you need to do is check if you have 5 volts standby, if you do not have 5v stby then check fuse FS802 if it is bad then icm801 is lkely bad.

Check if the small blue disc cap next to the ic is cracked or has a burn mark. sometimes this cap shorts.

Thanks for the reply. I'm going to remove it and put in a new one.
I'll be back!!

[snoptel]

Re: BN44-00301A No signs of life

the small cap near the center of the board starts the buck convertor chip to it's right on the heatsink, that generates your 5v standby.
i assume you pulled the fuses out and metered them?
you pull them out so you know that the clips are tight - just so you know.

Thanks for the reply. I'm assuming you mean the blue cap right?

[R_J]

Re: BN44-00301A No signs of life

You said you measured 400 volts at the bridge rectifier, to get this high a voltage the pfc circuit would be working, and for it to be working the standby circuit would also be working.
With the board unplugged Re check the voltage across CP802 OR CP803 (one of the main filter caps) this voltage should have drained down without the board plugged in, Then with the board plugged it check this voltage, if it is only around 160vdc, then the board in in standby, if it is around 385vdc then we know the pfc circuit etc is working.

[snoptel]

Re: BN44-00301A No signs of life

The power supply will not operate at all without the 5 volt standby circuit working. The standby circuit is very simple and only has a few components.
stj is likely referring to the electrolytic next to the ic (CM803?) it is on the ic's vcc line and if it is bad (basically open) it will not charge to maintain the startup vcc voltage for the ic.
Usually the blue ceramic disc cap blows up (cracks in half) if it is bad.
Sometimes it is only bad solder connections on the standby ic that cause this problem.

Thanks again.
Is this the section that you are referring to?

[R_J]

Re: BN44-00301A No signs of life

Thanks again.
Is this the section that you are referring to?

I changed my post after re reading your first post. Recheck the voltage ACROSS +/- of one of the main filter caps. If your voltage reading in the first post was correct, then the standby circuit must be working.

[snoptel]

Re: BN44-00301A No signs of life

I changed my post after re reading your first post. Recheck the voltage across one of the main filter caps. If your voltage reading in the first post was correct, then the standby circuit must be working.

Ok, I will go do that right now.
FYI - The measurements I take have been with the PS plugged in standalone, in other words, it isn't plugged into the video driver board or anything else. Not sure if that matters.
When I was installed in the TV, nothing happens, no standalone light..nothing..

[snoptel]

Re: BN44-00301A No signs of life

I changed my post after re reading your first post. Recheck the voltage ACROSS +/- of one of the main filter caps. If your voltage reading in the first post was correct, then the standby circuit must be working.

Confirmed, 316 VDC between positive and negative leg of each cap.

[R_J]

Re: BN44-00301A No signs of life

Does that voltage drop when you unplug the board? It might be just left over charge from when it was working.
Or just check if you have any voltages on CN801, you should have 5.1V and 13V

[snoptel]

Re: BN44-00301A No signs of life

You can check the voltages with the board out of the tv, Just be careful that fancy black and silver cloth is not conductive.

Haha, no worries. The cloth was just for the pic.

[snoptel]

Re: BN44-00301A No signs of life

Does that voltage drop when you unplug the board? It might be just left over charge from when it was working.
Or just check if you have any voltages on CN801, you should have 5.1V and 13V

Yes, the voltage drops almost right away after unplugging the cord.
Ok, let me go check CN801.
Be right back.

[R_J]

Re: BN44-00301A No signs of life

Yes, the voltage drops almost right away after unplugging the cord.
Ok, let me go check CN801.
Be right back.

This indicates the pfc circuit IS working, if it was not the voltage would only be 160vdc based on 120v A/C line voltage.

[stj]

Re: BN44-00301A No signs of life

Thanks for the reply. I'm assuming you mean the blue cap right?

no, the electrolytic with the rtv silicone stuck to it
next to jumper JP811