Samsung UE37C6000 blows fuses

[odg]

Hey guys, my Samsung LED TV UE37C6000 went black a few days ago. I found out that the 2 fuses of the power supply board PD37AF1E_ZDY were blown. I got new ones and both immediately blew again when I plugged the TV in.

I do not see (visually) any burnt components or any bad caps.

I have never identified such problem so I am rather clueless what to measure where and how to find the broken component(s). I guess it is some short circuit.

I hope someone can give me a hint. Thanks!

[R_J]

Re: Samsung UE37C6000 blows fuses

Check the resistance across VX801S MOV. The resistance should be high and not a short, I would then check the 4 diodes in the bridge rectifier BD801S

[budm]

Re: Samsung UE37C6000 blows fuses

Samsung BN44-00355B power supply board.
Check the bridge rectifier BD801S, MOSFET's QP801, QP802, QM803, QM804 for shorts.
Check the resistance between the two legs of those 3 main filter caps laying on the side.
Provide the straight shot of the whole bottom side of the power supply board, the pictures of the whole back side of the TV showing all the boards.

[odg]

Re: Samsung UE37C6000 blows fuses

Thanks for the hints. Very appreciated!!! I took some more pictures.

I checked the components (without desoldering):

Resistance across VX801S MOV is high.

The diodes of the bridge rectified BD801S all have a resistance of around 600 ohms, in both directions! I guess this is already a bad sign!? But I haven't desoldered it.

MOSFET QP801 has a short on all 3 pins
QP802 has a short on pin 2-3
QM803 and QM804 do not have any shorts

The 3 main filter caps:
CS801 is fine. CP803 and CP801 both have shorts

Should I already order some parts and replace all of those where the shorts are?

[budm]

Re: Samsung UE37C6000 blows fuses

I would removed QP801 first and test it off the board then re-test those that show as shorts again to see what you get without QP801 in place, it can be just one shorted out QP801 MOSFET for the PFC circuit.

[odg]

Re: Samsung UE37C6000 blows fuses

I removed QP801. It really has a short on all 3 pins. The remaining components i measured before now all seem to be ok. When eg. checking the big caps, my multimeter sometimes shortly beeps and then it stops, showing high resistance. It doesnt beep again. When I now switch the cables (so switching polarity) and test again, it again beeps shortly and stops etc.
Is this normal behavior because my multimeter maybe loads some caps or so? Or is there still something fishy on that board?

I will now get a new MOSFET and solder it in. Thanks a ton!!!! I will keep you posted.

[R_J]

Re: Samsung UE37C6000 blows fuses

If QP801 is shorted all around, it may have damaged icp801s, You should at least check the gate drive resistor and diode If CP813 is installed, check that it is not cracked or blown

[budm]

Re: Samsung UE37C6000 blows fuses

If QP801 is shorted all around, it may have damaged icp801s, You should at least check the gate drive resistor and diode If CP813 is installed, check that it is not cracked or blown

+1. I would replace the PFC IC too.

[odg]

Re: Samsung UE37C6000 blows fuses

> it may have damaged icp801s

I cannot find icp801s. I can only find ICP801. Is it the one you are talking about? I can't identify any shorts on ICP801.


> You should at least check the gate drive resistor and diode

DP803 also seems to have a short (that's the diode you meant, right?)

What type of component is BP802? It is connected to the gate of the broken MOSFET (if I am not mistaken) and also has a short.

Is RP821 the gate drive resistor you were talking about? That one is at 68 ohm although on the chip it says 680, but I am not sure if it maybe means 68.0?


> If CP813 is installed, check that it is not cracked or blown

CP813 is installed but looks good


> +1. I would replace the PFC IC too.

what is the PFC IC? Is it icp801s (which I can't find )

[odg]

Re: Samsung UE37C6000 blows fuses

I also found that all the 3 blue big resistors (RS807, RD849 and RD870) all have a short (i havent desoldered them). Should I also remove them and check again or could that be normal?

[R_J]

Re: Samsung UE37C6000 blows fuses

The resistors are ok, they don't short they go open. the values are less than 1Ω

[odg]

Re: Samsung UE37C6000 blows fuses

Alright. Thanks. Could you please have a look at those questions again?

> it may have damaged icp801s

I cannot find icp801s. I can only find ICP801. Is it the one you are talking about? I can't identify any shorts on ICP801.


> You should at least check the gate drive resistor and diode

DP803 also seems to have a short (that's the diode you meant, right?)

What type of component is BP802? It is connected to the gate of the broken MOSFET (if I am not mistaken) and also has a short.

Is RP821 the gate drive resistor you were talking about? That one is at 68 ohm although on the chip it says 680, but I am not sure if it maybe means 68.0?


> If CP813 is installed, check that it is not cracked or blown

CP813 is installed but looks good


> +1. I would replace the PFC IC too.

what is the PFC IC? Is it icp801s (which I can't find )

[R_J]

Re: Samsung UE37C6000 blows fuses

ICP801 (on some boards it is called icp801S) Look at its number, find the datasheet and check the parts between the ic's output pin and the blown fet's gate pin. (this is the PFC ic)
The diode I ment would be located between the gate and ic output.
If DP803 checks shorted, remove one end and check it out of circuit, if the diode is ok, something else in the circuit could be shorted.
I mentioned cp813 because on some similar boards a similar (usually blue) cap can short or sometimes blows completely.
RP821 marked 680 = 68Ω, the third number is the multiplier 681 would be 680Ω

[odg]

Re: Samsung UE37C6000 blows fuses

The numbers on ICP801 were really hard to read. I believe it said 5591 and I found https://www.alldatasheet.com/datashe...JI/FA5591.html which is also a PFC. So maybe correct, but I am not 100% sure.

That one has it's output on pin 7. I think there is no diode on the path from pin7 to the blown FET's gate pin. I drew the path onto the attached image. I havent found any shorts in that area

I removed DP803 and it was shorted.

What do you think? Should I give it a try with the new QP801 and DP803. Maybe with a light bulb as current delimiter?

[R_J]

Re: Samsung UE37C6000 blows fuses

Yes give it a try, likely dp803 shorted and took out the pfc fet

[budm]

Re: Samsung UE37C6000 blows fuses

https://www.badcaps.net/forum/attach...9&d=1561063940
Looking at the picture, you can see that QP801 and QP802 are basically connected in parallel as far as the Source and Drain are concerned, you can see the Gate pin of QP802 is connected to diodes and resistors and then it goes to the IC which I cannot see the traces well, I see DPxxx around the Gate circuit of Q801 also.
You can try just replacing the MOSFET and see what happen.

[odg]

Re: Samsung UE37C6000 blows fuses

So i finally got a new diode and MOSFET and soldered them in. I powered the TV with a lightbulb in series. The result was, that I heard a relay clicking, the lightbulb lightening up for a second, the relay clicked again and the lightbulb went dark. This repeats indifinetely, 1s on, 1s off, ...

When I power it on without connecting the power supply board to the other 2 boards of the TV, nothing happens, no relay clicking, lightbulb stays dark.

Do you think its the PFC? I guess if I didnt had the lightbulb in series, sonething would have blown up again, right?

[odg]

Re: Samsung UE37C6000 blows fuses

The numbers on ICP801 were really hard to read. I believe it said 5591 and I found https://www.alldatasheet.com/datashe...JI/FA5591.html which is also a PFC. So maybe correct, but I am not 100% sure.

I now wanted to replace the PFC IC but I really couldn't read the numbers to order a new one. Do you have any idea how to find the exact name of it?

[odg]

Re: Samsung UE37C6000 blows fuses

The furthest I got was reading these numbers for the PFC IC ICP801:

either it is
1D10123
5591

or
1510123
5591

or
1010123
5591

when I google for any of the first numbers, i cannot find anything meaningful. If i search for 5591 PFC i find this: https://www.alldatasheet.com/datashe...JI/FA5591.html

So I believe this should be it.

[R_J]

Re: Samsung UE37C6000 blows fuses

Yes, its a FA5591, the top number is the mfg/date code