Samsung UN60KU6270FXZA dead, no stby light, diagnostic complete, a couple questions.

[DXseekerMO]

Hello everyone, long time no see! I have a few questions about a power board I'm working on and was hoping to field some answers.

MAKE: Samsung
MODEL: UN60KU6270FXZA
VERSION: EA01
POWER BOARD P/N: BN44-00808D

SELLER COMPLAINT: Sound volume became unstable for a brief instance, TV shut off, became unresponsive and appeared dead.

INITIAL INSPECTION: Main fuse FP801S (T8.0AH/250V) open, Thermistor NT811S 7.5ohms across legs, board there has a slight brown discoloration, rectifier diode indicates short across DC legs, main caps indicate short across both legs, MOSFET QP801CS (60R360P) indicates short, Diode DP807C (SF10A600HPL) indicate short, MOSFET QP802CS (60R360P) indicates short on drain and source. Items circled in red.

DIAGNOSTIC FLOW: Remove QP801CS, tests short. Re-test DC legs of rectifier diode and legs of both main caps, short cleared. Rectifier diode tests OK. DP807C still indicates short, QP802CS still indicates short on drain and source. Remove DP807C, tests short. Re-test QP802CS in-circuit, short on drain and source cleared. Test all components off gate of both MOSFETS, all appear good.

ACTION TO BE TAKEN: Replace QP801CS, QP802CS, DP807C and main fuse.

ACTIONS CONSIDERED: Precautionary replacement of NT811S

Questions:

With QP801CS, DP807C shorted and components off both gates of QP801 and QP802CS testing OK is it necessary to replace PFC IC ICP801 (6BA3G2M SPC1012T, circled in yellow)?

Have I missed anything else I should be checking with the above failures present?

Thank you everyone for the help!

[budm]

Re: Samsung UN60KU6270FXZA dead, no stby light, diagnostic complete, a couple questio

I would replace the PFC IC too, it is not worth taking an chance of blowing the new parts you replace.

[DXseekerMO]

Re: Samsung UN60KU6270FXZA dead, no stby light, diagnostic complete, a couple questio

Thanks budm! One last question. Is the clear silicone surrounding the PFC IC required to be replaced after service? I'll have to scrape it off to replace that IC. If so can you suggest a product for that?

Wishing for you a happy Thanksgiving!

[Storyteller12]

Re: Samsung UN60KU6270FXZA dead, no stby light, diagnostic complete, a couple questio

I have the same problem and have replaced the mosfet. However having a hard time finding
SF10A600HPL Or replacement.

Maybe I’m searching wrong, but cannot find a suitable replacement. Any help would be appreciated. Thanks n advance.

[diif]

Re: Samsung UN60KU6270FXZA dead, no stby light, diagnostic complete, a couple questio

I have the same problem and have replaced the mosfet. However having a hard time finding
SF10A600HPL Or replacement.

Maybe I'm searching wrong, but cannot find a suitable replacement. Any help would be appreciated. Thanks n advance.

Search for SF10A600H.

[Storyteller12]

Re: Samsung UN60KU6270FXZA dead, no stby light, diagnostic complete, a couple questio

Will do. Thanks for the reply

[Davi.p]

Re: Samsung UN60KU6270FXZA dead, no stby light, diagnostic complete, a couple questio

check the varistor...

[Storyteller12]

Re: Samsung UN60KU6270FXZA dead, no stby light, diagnostic complete, a couple questio

check the varistor...

Are you referring to the thermistor mentioned in the original post?

If not please specify the varistor you mention. Sorry I'm kind of a noob at all this, teaching myself along the way.

Thanks

[Davi.p]

Re: Samsung UN60KU6270FXZA dead, no stby light, diagnostic complete, a couple questio

near the AC input, that green disk, must show open in ohm..

[Storyteller12]

Re: Samsung UN60KU6270FXZA dead, no stby light, diagnostic complete, a couple questio

Thanks for the reply. Will check that as well

[Storyteller12]

Re: Samsung UN60KU6270FXZA dead, no stby light, diagnostic complete, a couple questio

Ok. The. Varistor is good. However I replace the Mosfets and the double diode rectifier and when powered up without main board hooked up I get backlights flashing on and off.

Good news is the fuse doesn’t blow anymore. Can someone confirm the parts I used are correct.

I could not locate the original parts so had to find replacements.

For the 60r360p Magnichip I relaxed both with IPA60R360P7SXKSA1 from mouser and for the SF10A600H I replaced it SFF1008GA C0 from mouser also.

Appreciate the help

[Storyteller12]

Re: Samsung UN60KU6270FXZA dead, no stby light, diagnostic complete, a couple questio

Also I can confirm it’s not the backlights as I have another power board I installed and the tv works just fine.

[Davi.p]

Re: Samsung UN60KU6270FXZA dead, no stby light, diagnostic complete, a couple questio

you have probably an intermittent short on secondary, first disable the backlight by pulling down the bl on command, then test the psb to mb connector without and with dummy loads, if all is well check mosfet/diodes of the led driver section, if not check all diodes, if good replace el. condensers

[lotas]

Re: Samsung UN60KU6270FXZA dead, no stby light, diagnostic complete, a couple questio

If the backlight blinks, then most likely the PFC does not work (it does not hold the load), what is the voltage on your CP810, CP811 capacitors?

[Storyteller12]

Re: Samsung UN60KU6270FXZA dead, no stby light, diagnostic complete, a couple questio

Plugged it in and tested the main caps cp810 and power was fluctuating up and down to 0.

Right after that test sparks flew. Fuse blown amd 1 of the mosfets I replaced 60s360p blew up.

Checked the other mosfet and the rectifier I replaced and they are still test good.

[lotas]

Re: Samsung UN60KU6270FXZA dead, no stby light, diagnostic complete, a couple questio

There is a high voltage on these capacitors, provided that the input voltage AC 220v on them should be in standby mode DC 300-320v, in working mode about DC 400v (PFC (Power Factor Correction) starts to work), and the fact that sparks have occurred, then rather you closed these conclusions "+" and "-" among themselves.

[DXseekerMO]

Re: Samsung UN60KU6270FXZA dead, no stby light, diagnostic complete, a couple questio

I realized as the OP I didn't update this thread. I had a TV come in for parts that had this power supply in it. I used its power supply to repair this TV.

Plugged it in and tested the main caps cp810 and power was fluctuating up and down to 0.

Right after that test sparks flew. Fuse blown amd 1 of the mosfets I replaced 60s360p blew up.

Checked the other mosfet and the rectifier I replaced and they are still test good.

Did you accidentally short the + and - on the main capacitors? If not then it sounds like the PFC IC may be short

There is a high voltage on these capacitors, provided that the input voltage AC 220v on them should be in standby mode DC 300-320v, in working mode about DC 400v (PFC (Power Factor Correction) starts to work), and the fact that sparks have occurred, then rather you closed these conclusions "+" and "-" among themselves.

Main cap voltage in stand-by is around 165v DC and 380-400V when the TV is on.

Sorry I haven't been so good with updating my posts. I recently had a stroke and have been in recovery.

[Storyteller12]

Re: Samsung UN60KU6270FXZA dead, no stby light, diagnostic complete, a couple questio

I didn’t short anything out when it blew up. I took the first measurement the had a phone call.

While I was on the phone it blew up. I suspect you are right about the pfc ic and when I was removing it I had the board “popcorn” I believe is the correct word around the ic.

I’m guessing the boards trash now.

At least I had a backup power supply. I was just trying fix this one.