Samsung UN60D8000YF Clicking BN44-0432A

[mikelu53]

I have a UN60D8000YF with a BN44-0432A power supply and a BN41-01622C main board.
The set was working then not,then started clicking.
Wilth the power supply disconnected from the main board I can occasionally get it to power the LED back lights , getting it to stop clicking is luck.
Checked caps and diodes and mosfets the best I could. When it stop clicking there is 5v and 18v on the connector to the main board.
A schematic or suggestion would be great.
Thanks

[R_J]

Re: Samsung UN60D8000YF Clicking BN44-0432A

Do you have a constant A5V +5 volt standby? Use HS804 (heat sink) and check the voltage on BBS851 or BB852 (both are in parallel)]
I would replace CS802 and CS805

[mikelu53]

Re: Samsung UN60D8000YF Clicking BN44-0432A

The 5 volts is not constant while the relay is clicking, changed the caps, still a problem.
Tried to ground and +4.5 the power on pin 28, with no effect. When the click stopped I could turn the PS on/off with pin 28, back lights would then come on as I am guessing they should.

I am guessing the clicking is some kind of startup sequence that is failing, and it keeps restarting.
Second I am guessing you can start the PS without the main board attached.

[R_J]

Re: Samsung UN60D8000YF Clicking BN44-0432A

Check that there are no shorted diode in the secondary of the main transformer, check that the solder connections are ok on tm801s
Check that NT813S (thermistor) is not bad or open.
Also make sure you disconnect the led's from the power supply in case they are causing the problem.

[mikelu53]

Re: Samsung UN60D8000YF Clicking BN44-0432A

Have checked all diodes (using diode test on meter), re flowed solder on all transformers, NT813S reads 33ohms in the circuit. LED are not connected. When it dose stop clicking 5v on DS853, 18v on DM853, 12v on DM854,855, 88v on dm852

thanks

[R_J]

Re: Samsung UN60D8000YF Clicking BN44-0432A

The relay is clicking because it is either loosing its supply voltage or the transistor that turns it on is being turned off.. You could try and eliminate CS855 and CS857 as not the issue by bridging them with another 100µf/ Connect it between hs804 and BBS852.
Can you place the power supply in standby by grounding the Power On/Off pin.

[mikelu53]

Re: Samsung UN60D8000YF Clicking BN44-0432A

With the PS commanded to off, all is stable +5 is good, as soon as commanded to turn on by removing the ground, all is bad +5 jumps as before.
When power is removed the clicking continues for at least 10sec or more.

Also tried to short the relay contacts, no change

[R_J]

Re: Samsung UN60D8000YF Clicking BN44-0432A

So everything is stable in standby, but when the main pwm ic and pfc circuit start the power supply is unstable, Can you check the VCC voltage across CP805 and see the value and if it is stable?

[mikelu53]

Re: Samsung UN60D8000YF Clicking BN44-0432A

The voltage is a solid +15

FYI

I Lifted fuse FP8035, and the on/off turns the relay on a off (no clicking), so what ever I disconnected seems to be the problem, the +5 is stable. I probably disconnected the whole cold side.

[R_J]

Re: Samsung UN60D8000YF Clicking BN44-0432A

That vcc voltage is likely ok
FP803S is in the supply voltage line for the main switching mosfets for the main transformer. I wonder if it could be CS818 at fault Unlikely but you never know? There are also a number of diodes in the line, DS810, DS811 etc. I wonder if one of them might be bad?

Or it could be that CM809 or CM806 are weak, they are likely for the main pwm controller vcc. If one of them is weak the the ic will start, fail and restart. If it is a SEM3110, I believe the ic's turn off on the vcc is about 9v and turn ON about 10.5v

[mikelu53]

Re: Samsung UN60D8000YF Clicking BN44-0432A

I appreciate your help, but would you be willing to share the schematic I assume your are looking at? I would not redistribute it, just for my use.

I have lifted many caps and diodes, a few legs of mosfets, but no smoking gun

Again thanks

[R_J]

Re: Samsung UN60D8000YF Clicking BN44-0432A

This is what I am using, there are no schematics for this model

[mikelu53]

Re: Samsung UN60D8000YF Clicking BN44-0432A

Wow, I would have bet big saying you had a schematic.
The only time I go it to stop clicking is when I probed the iso isolator 8035 near the center of the board.

Was going to try a short the output to fake a good signal, to see what happens
I am thinking the feedback voltage is flaky, have found other schematic that kind of have the same parts 0BN44-00357B

I am testing caps with a cap function of the volt meter, don't have a ESR meter

[R_J]

Re: Samsung UN60D8000YF Clicking BN44-0432A

What do you mean by

when I probed the iso isolator 8035 near the center of the board

Probed with what, meter? and which pins did you probe and where was your meter ground? (hot ground or cold ground)

You can't check caps with a meter very accurately, The best way would be to use a scope or just replace them.

[mikelu53]

Re: Samsung UN60D8000YF Clicking BN44-0432A

The meter only check cap not the internal resistance, I had a esr meter but, it died, it was $5

Anyway I put a 10uf cap from the cathode (led side) of the isolator 8035 to cold side ground, every thing worked even the TV itself, how ever after about 5 min it didn't.

So atleast I know the rest of the set is ok.

I opto is controlled by the 12volt output thru a bunch of resistor and smd caps.
going to recheck the 12voltage output caps, tried to parallel a bigger cap but no luck
Have a new ESR meter on the way

[mikelu53]

Re: Samsung UN60D8000YF Clicking BN44-0432A

Still at it, found a schematic that is close bn44-00428b.pdf, I opened fuse fp80835 which supply's the PFC to the main output, clicking stopped. With the fuse inplace the PFC voltage jumps around. I tried to measure the PFC current to the main output, which seems to go up to the 12A range, I guess it shuts down fast enough to not blow the fuse.

Have checked components around the controlling IC "UCC25600 8-Pin High-Performance Resonant Mode Controller". Shorting out the opto for this chip shuts it down and stops the jumping.

Have not found any bad components yet, don't know why the current is so high that it pulls down the PFC.