Samsung UN55EH6000F Power issue

[R_J]

Re: Samsung UN55EH6000F Power issue

Zero volts 5 nor 13 when when PS_ON/OFF jumped to ground.

You will not get B5V or B13V but you should get A5V (JP809) with the board turned off

[CraigR]

Re: Samsung UN55EH6000F Power issue

You will not get B5V or B13V but you should get A5V (JP809) with the board turned off

Ok, yes I get 5v on JP809 with it jumped.

[R_J]

Re: Samsung UN55EH6000F Power issue

Ok, yes I get 5v on JP809 with it jumped.

when you remove the jumper does the A5V stay at 5volts? or does it drop? If it drops I suspect the standby circuit is not supplying enough voltage to keep itself and the pfc circuit working.

[CraigR]

Re: Samsung UN55EH6000F Power issue

Yes, it stays at 5v

[CraigR]

Re: Samsung UN55EH6000F Power issue

I'm now just guessing at things and tested this resistor RP820 and out of circuit it's 0.11 but I can not find a chart online that the colors work with. Under the scope it looks black, gold, black, gray, black. but this comes as an error on the calculators.

[R_J]

Re: Samsung UN55EH6000F Power issue

with power supply on, Check the voltage across the main filter capacitor CP806

This voltage should be around 165vdc in standby and go to around 300vdc when the power supply is on.

[R_J]

Re: Samsung UN55EH6000F Power issue

I'm now just guessing at things and tested this resistor RP820 and out of circuit it's 0.11 but I can not find a chart online that the colors work with. Under the scope it looks black, gold, black, gray, black. but this comes as an error on the calculators.

The resistor is ok. That is the source resistor for the pfc mosfet.

[CraigR]

Re: Samsung UN55EH6000F Power issue

with power supply on, Check the voltage across the main filter capacitor CP806

This voltage should be around 165vdc in standby and go to around 300vdc when the power supply is on.

172v in standby and 386v on.

[R_J]

Re: Samsung UN55EH6000F Power issue

If the PFC voltage 386vdc is steady, that means the standby circuit and the pFC circuit are working as they should.

[CraigR]

Re: Samsung UN55EH6000F Power issue

Ok, so now what can I check?

[R_J]

Re: Samsung UN55EH6000F Power issue

I don't have a schematic, I am using the pictures of the board. I would try grounding the BLU_ON/OFF pin CNM803 pin6 and see if the B5v and B13v stay up

It might be that the backlight drive circuit is killing the B13v?

[CraigR]

Re: Samsung UN55EH6000F Power issue

I don't have a schematic, I am using the pictures of the board. I would try grounding the BLU_ON/OFF pin CNM803 pin6 and see if the B5v and B13v stay up

They do! they stay normal now.

[R_J]

Re: Samsung UN55EH6000F Power issue

So when the backlight circuit is turned on there is too much load on the supply, Back to post 1 where the two mosfets were replaced, It could be that they are being turned on hard and killing the supply. There are also a pair of dual diodes, DL851 & DL852, I would check them as well

This is a guess but it might be caused by open led's in the panel and the board is shutting down due to an over voltage on the led supply.

[CraigR]

Re: Samsung UN55EH6000F Power issue

Just pulled them and checked with component tester and good.

[R_J]

Re: Samsung UN55EH6000F Power issue

What voltage do you get on JP840 when the backlight circuit is enabled (BLU_ON/OFF ground removed) Does it jump up to 300vdc? or is it higher? If it jumps up higher, connect the backlights and check the voltage again.

[CraigR]

Re: Samsung UN55EH6000F Power issue

On JP840 I get voltage up and down. but with BLU_ON/OFF jumped to ground I get no volt. Is that what you wanted to know?

[R_J]

Re: Samsung UN55EH6000F Power issue

Yes, when you say you get voltage up and down can you give a number?

[CraigR]

Re: Samsung UN55EH6000F Power issue

from 54v to 11v constant fluctuation.

[R_J]

Re: Samsung UN55EH6000F Power issue

That is way too low, I suspect there is still a problem with the mosfets QL801 & QL802 or there gate drive circuit.

[CraigR]

Re: Samsung UN55EH6000F Power issue

QL801 and QL802 are new.