Samsung Bn4400612b Power Supply issue on Samsung UN50F6300

[captainKKK]

Samsung Bn4400612b Power Supply issue takes out a new 5A fuse on my Samsung UN50F6300, without any the BL or main board cables connected. Please advise if this board has known issues and fixes. There are no evident fried components and the caps look ok. Nothing unusal on the bottom side of the board under magnification. Is the ICM801CS under that heat sink a known issue? SJ (https://www.shopjimmy.com/samsung-bn...-1473373576096) out of stock, so component level repair may be my best shot. Thanks.

[neilc6]

Re: Samsung Bn4400612b Power Supply issue on Samsung UN50F6300

Fuses typically blow due to shorted FETs or power diodes. I would check the ones mounted on heatsink which is probably the switching FET for the PFC circuit. The short can be measured with your multimeter. If a FET is shorted, it introduces unexpected high voltages to the gate side of the FET and can damage components in that section as well.

[R_J]

Re: Samsung Bn4400612b Power Supply issue on Samsung UN50F6300

Check for a shorted VX801s mov, then check for a shorted BD801s bridge rectifier, check the pfc mosfet (and small blue disc cap)then check for a shorted icm801cs Check pins 1 to 10 and 6 to 10.

[captainKKK]

Re: Samsung Bn4400612b Power Supply issue on Samsung UN50F6300

IF the only thing bad was this MURF860, would this always cause the fuse to blow as soon as power was applied?

[dskall]

Re: Samsung Bn4400612b Power Supply issue on Samsung UN50F6300

Since they seem to have a repair kit. I would say there are known issues.

[captainKKK]

Re: Samsung Bn4400612b Power Supply issue on Samsung UN50F6300

Since they seem to have a repair kit. I would say there are known issues.

Yeah but there are no repair kits nor PS boards available from any reliable sources...so I am try to rebuild.....it seems the MURF860 might be bad but I am not sure.

[dskall]

Re: Samsung Bn4400612b Power Supply issue on Samsung UN50F6300

A good place to start is to look at repair kit and check those components.

[captainKKK]

Re: Samsung Bn4400612b Power Supply issue on Samsung UN50F6300

So, I lied. Well not exactly, there were no burnt or physically damaged components that I could see. Turns out the ICM801CS has LOTS of damage. It was hiding under its heat sink. After digging all the silicone rubber off and testing shorts, 8 of the nine pins were shorted. Since this is a Fairchild FSFR1700HSL which is no longer manufacturered and Mouser and DigiKey has no stock, I turned to ebay and aliexpress. Seems the FSFR1700HSL is 3 times the price of the FSFR1700XSL. And since I am nothing more than a hack, I am struggling to determine whether they are interchangeable? Another issue for thought is if that blew...see pics...what else is likely to go down with it?

[R_J]

Re: Samsung Bn4400612b Power Supply issue on Samsung UN50F6300

I see a difference between the HS and XS with pin 2. I would likely go with the FSFR1800HSL About $5.00 from Digikey
The 1800 has a lower RDSon but should not be a problem.

This ic drives a transformer so check the diodes etc. on the transformer secondary in case something was shorted, but it is likely it was just the ic that went bad.

[dskall]

Re: Samsung Bn4400612b Power Supply issue on Samsung UN50F6300

Might check this one.
https://www.mouser.com/ProductDetail...ppqY8SPpufs%3D

[captainKKK]

Re: Samsung Bn4400612b Power Supply issue on Samsung UN50F6300

Can any one please help me find a substitute for the DM851C = STPS20LCD80C

[captainKKK]

Re: Samsung Bn4400612b Power Supply issue on Samsung UN50F6300

Can any one please help me with instructions to test the DM851C = STPS20LCD80C and then maybe and find a substitute?

[lotas]

Re: Samsung Bn4400612b Power Supply issue on Samsung UN50F6300

It is checked, as usual, the diode, one then the second.

[captainKKK]

Re: Samsung Bn4400612b Power Supply issue on Samsung UN50F6300

It is checked, as usual, the diode, one then the second.

So, with it in circuit, multimter on diode mode, positive lead on the center pin, and the negative on each outer pins results in 0.413 on each of the outer leads. Reversing the leads gives 0.216 on each of the outer pins. Leads connected to the outer pins shows continuity.

If this means it is bad, this is going to kill my project, because I cannot find a STPS20LCD80C anywhere, not even on Aliexpress. CAn anyone sugest a viable substitute?

[lotas]

Re: Samsung Bn4400612b Power Supply issue on Samsung UN50F6300

t is better to check this diode in a non-circuit, that is, it must be removed from the board and checked.

[Diah]

Re: Samsung Bn4400612b Power Supply issue on Samsung UN50F6300

STPS20LCD80C was used too at primary PCB circuit CRT Tv philips.. its come with kit if my memory correct it will be 2R and C ceramic and caps. let see tomorrow my old box if i find one for you.

[captainKKK]

Re: Samsung Bn4400612b Power Supply issue on Samsung UN50F6300

t is better to check this diode in a non-circuit, that is, it must be removed from the board and checked.

Ok I will remove it to check again. I found this on an old board, but I do not have enough knowledge to determine if it substitutes:
https://cdn.badcaps-static.com/pdfs/...8e914494a2.pdf

for what I have:
https://cdn.badcaps-static.com/pdfs/...d66b0adcaa.pdf

Update:
I removed the STPS20LCD80C from circuit (thanks lotus) and with the negative black lead in the middle, the outside leads read 0.240 to each. Placing the positive red lead in the middle, there is no continuity to ether of the outside leads, nor between the outside leads.

Therefore, I will reinstall the STPS20LCD80C and the new FSFR1800HSL that I just received today, along with my last 5 amp fuse and hope for the best.....
I was trying to remember the use of the light bulb for the fuse, but for the life of me I cannot find it.

Thanks to all, will report later...

Thanks to everyone with your help

[lotas]

Re: Samsung Bn4400612b Power Supply issue on Samsung UN50F6300

You need a Power Schottky rectifier which has a low junction resistance.
Can replace with MBR20100CT

https://www.youtube.com/watch?v=1KVBZSTY7FE

[captainKKK]

Re: Samsung Bn4400612b Power Supply issue on Samsung UN50F6300

Thanks guys, it's fixed with a $3 part and all YOUR knowledge....not by me😀

[nomoresonys]

Re: Samsung Bn4400612b Power Supply issue on Samsung UN50F6300

So a bad ICM801CS was the only thing wrong?