Samsung Power Supply Board BN44-00874F

[Nicktronic]

It was Nicks datasheet that said 12 pin is VCC.

I just checked again, what lotas posted in #23 is from the document I attached. 10 is VCC. Regardless, I will check what you suggested in post #24, thank you.

Does the 7VDC on FB indicate a problem?

[nomoresonys]

It was Nicks datasheet that said 12 pin is VCC.

[nomoresonys]

Ok, not exactly sure but might be able to get a clue by testing resistance from neg. leg of filter cap to pin 10 VCC, see what you get, done with tv unplugged from power.

[lotas]

12 pin is GND, and VCC is 10 pin.

[nomoresonys]

So you're saying the datasheet you posted is not the right one?

[nomoresonys]

Is it fair to say ICM801CS (FA6B22N, cannot find a datasheet) should be driving QM801CS and QM802CS when the board is in standby? It's switching the 170vdc of the filter caps, to ultimately provide an unboosted VDC on the output connector (7ish volts)?

In the current state with the board on the bench and plugged in, on ICM801CS pins:

1 - 68-69VDC
2 - 0vdc
3 - 0vdc
4 - 7.2VDC
5 - 0vdc
6 - 0vdc
7 - 0vdc
8 - 0vdc
9 - 0vdc
10 - 10VDC
11 - 0vdc
12 - GND
13 - 0vdc
14 - 8VDC
15 - 8VDC
16 - 10VDC

https://products.fujielectric.com/en...etail/FA6B22N/

This link is the most info I could find for this IC.

Thoughts?

Something doesn't seem to be matching, you have pin 12 as GND but in the datasheet you posted, pin 12 is VCC.

[lotas]

FA6B22N can be replaced with FA6B20N, not much information...

[Nicktronic]

Sure, couldn't hurt to check them.

I did, and couldn't find anything...

[Nicktronic]

Check the markings on those resistors, if it's a 0 ohm resistor then its ok.

Markings indicate 0.25 ohms, and two in parallel, so 0.125ohms

[Nicktronic]

Is it fair to say ICM801CS (FA6B22N, cannot find a datasheet) should be driving QM801CS and QM802CS when the board is in standby? It's switching the 170vdc of the filter caps, to ultimately provide an unboosted VDC on the output connector (7ish volts)?

In the current state with the board on the bench and plugged in, on ICM801CS pins:

1 - 68-69VDC
2 - 0vdc
3 - 0vdc
4 - 7.2VDC
5 - 0vdc
6 - 0vdc
7 - 0vdc
8 - 0vdc
9 - 0vdc
10 - 10VDC
11 - 0vdc
12 - GND
13 - 0vdc
14 - 8VDC
15 - 8VDC
16 - 10VDC

https://products.fujielectric.com/en...etail/FA6B22N/

This link is the most info I could find for this IC.

Thoughts?

[nomoresonys]

All the FETS are good, no shorts. Should I check all the transistors on the underside of the board too?

Sure, couldn't hurt to check them.

[nomoresonys]

The IC is ICP801S, UCC28064A G4, datasheet attached.

The resistors beside QP801CS appear to be 0.25ohm each, but when measured out of circuit, both are dead short(0.01ohms each)

QP804 seems ok and the resistors around it are good.

Check the markings on those resistors, if it's a 0 ohm resistor then its ok.

[Nicktronic]

Maybe do a quick ohm check of CM185, CM810 and CM814.

They all measure good.

[Nicktronic]

Not exactly sure, but CP801S and CP802S may need to be checked.

They are 1uF each and measure 2.1uF in parallel. Seems ok.

[Nicktronic]

To be clear, you replaced the parts with the correct part and after trying tv again, none of the parts are reading bad again, fuse didn't blow etc?

Correct

[Nicktronic]

Go ahead and check all the transistors, thats all that start with Q for a short if you haven't already. For those that may be looking on and need to know. Put meter in beep mode, thats the one with the diode on some meters and check each of the three legs for a short, so one probe on leg 1 the other on leg 2 then 3, then go from 2 to 3, if you get a constant beep its shorted. If meter has no beep mode, you can test in ohm mode, if you get close to 0 ohms while doing the same test its shorted.

All the FETS are good, no shorts. Should I check all the transistors on the underside of the board too?

[Nicktronic]

I see, I would probably suspect the IC nearby QP802CS, the one with 14 legs there and maybe check the resistors by your mosfet, and maybe QP804 and the ones near it. See if you can grab a datasheet for that IC.

The IC is ICP801S, UCC28064A G4, datasheet attached.

The resistors beside QP801CS appear to be 0.25ohm each, but when measured out of circuit, both are dead short(0.01ohms each)

QP804 seems ok and the resistors around it are good.

[nomoresonys]

Maybe do a quick ohm check of CM185, CM810 and CM814.

[nomoresonys]

Not exactly sure, but CP801S and CP802S may need to be checked.

[nomoresonys]

To be clear, you replaced the parts with the correct part and after trying tv again, none of the parts are reading bad again, fuse didn't blow etc?