TV Samsung 75F6400AFXZA Power Supply BN44-00621A Dead

[alfredomfr1]

Power Supply BN44-00621A Dead, no voltages on CM803, fuses OK, Transistors with heatsink OK, Diodes OK.

[petehall347]

Re: TV Samsung 75F6400AFXZA Power Supply BN44-00621A Dead

what voltage are you seeing at the big caps bottom right picture 3 ? this is the rectified mains power if no voltage check between there and the mains power socket there should be a rectifier .

[R_J]

Re: TV Samsung 75F6400AFXZA Power Supply BN44-00621A Dead

Check the voltage ACROSS one of the primary caps CP800,CP802 or CP804, (Next to the word BONDING) should be around 165vdc. If you have that voltage, check the voltage ACROSS CS851, this should be your standby A5V, this voltage needs to be there before anything will work.

[alfredomfr1]

Re: TV Samsung 75F6400AFXZA Power Supply BN44-00621A Dead

0v across the main capacitors.

[R_J]

Re: TV Samsung 75F6400AFXZA Power Supply BN44-00621A Dead

Check the voltage ACROSS CS809, this is the standby circuit supply voltage (165VDC), if not, check that you have A/C voltage on the inlet plug, I suspect you might have broken solder connections or broken traces on the plug where it connects to the board.

[alfredomfr1]

Re: TV Samsung 75F6400AFXZA Power Supply BN44-00621A Dead

I have voltage thru the fuse but the bridges have not voltages

[alfredomfr1]

Re: TV Samsung 75F6400AFXZA Power Supply BN44-00621A Dead

let me rectify, between live (L) and both AC legs of the bridge I have 120v but between Neutral (N) and the bridge I have 0v

[alfredomfr1]

Re: TV Samsung 75F6400AFXZA Power Supply BN44-00621A Dead

Relays are not receiving the 5v DC.

[R_J]

Re: TV Samsung 75F6400AFXZA Power Supply BN44-00621A Dead

I will try again... Check the voltage ACROSS CS809, this is the standby circuit supply voltage (165VDC)
Are you sure FS801S is good and not open?

If you have voltage across CS809, leave your negative probe on CS809 (EY16) cnd check the voltage on JP910 (DS802 cathode), there should be around 25vdc

[alfredomfr1]

Re: TV Samsung 75F6400AFXZA Power Supply BN44-00621A Dead

CS809: 157v DC
JP910: 0v

[R_J]

Re: TV Samsung 75F6400AFXZA Power Supply BN44-00621A Dead

You should have that 157v on the 3 pins (6,7,8?) of ICS801CS If you do I suspect the ic is bad, it could be that CS806 is bad but not likely, Also check that the 5v output diode, DS851C is not shorted. You will need to remove it's heat sink to see the number.

[alfredomfr1]

Re: TV Samsung 75F6400AFXZA Power Supply BN44-00621A Dead

ICS801C is SQD2011K, it is receiving 157v but nothing is coming out, DS851C is OK

[R_J]

Re: TV Samsung 75F6400AFXZA Power Supply BN44-00621A Dead

It is a very simple circuit, so if it is getting Drain voltage, check that the CS resistor RS807 is ok and not open, if it is ok, it is likely that the ic is bad, there could be a zener diode between pins 3 & 4, make sure it is not shorted.
Here is a similar circuit using that ic.

[alfredomfr1]

Re: TV Samsung 75F6400AFXZA Power Supply BN44-00621A Dead

ICS801C replaced.
Thanks to you R J the board is working.

[R_J]

Re: TV Samsung 75F6400AFXZA Power Supply BN44-00621A Dead

Good to here it's fixed, glad I could help.

[Gymkata98]

Hi Alfredomfr1 and R_J. I am a little late to the party on this post, so I'm not sure if anyone will respond, but I thought I would try! I am very much so a novice at troubleshooting Samsung Power Boards. This was a 75” TV that had a good screen, so I really wanted try and fix it. The board is BN44-00621C, but I think it is very similar to the “A” version. When Plugged in, the TV turns on and shows “Samsung smart tv” and then immediately the relay clicks and it turns off. It does this loop forever. If I unplug it, it will suck the voltage from the filter Caps and continue to power cycle until it does go into Power Standby (safety mode I suppose?) and show 2 quick flashing red lights until it runs out of juice.

I have check all resistors, fuses, diodes, transformers, solder joints, MOSFETS (although I'm not very knowledgeable at this). I have replaced almost all the Caps that I had in stock to match the best I could with what was on the board. I didn't replace the filter Caps, but I don't think they are bad. R_J, the voltage across the Filter Caps is only around 12 VDC before it shuts off, so the TV never stays on long enough for me to get a good reading. I checked voltage across CS809 and get around 365 VDC before relay shuts off (I replaced this CAP as it looked leaky at the Anode base. I only had a 37 mf cap, not a 22 mf). I also check the voltage across DS8021 did have around 25 VDC and DS851C does have 5 VDC.

Thank you and anything pointers you have would be greatly appreciated as I don't want to throw this old 75” TV in the Garbage!!

[alfredomfr1]

Disconnect the LVDS cable, turn on the TV and check if screen light on