Samsung UN55ES7100 Blinking front light and no backlight - clicking

[jason123]

Unless I'm mistaken, these Samsung TVs typically turn the backlight on when main to PS cable is disconnected.
This TV does not. Tested the backlight (edge) and they all seem to turn on.

There doesn't seem to be power to the backlight from the PS. measurement of few mV.

Main caps only have 162 VDC on them.

I'm assuming the PFC is not kicking in / working?

I'd like to fix the board (BN44-00523A), but I haven't had much luck with a schematic.

[R_J]

Re: Samsung UN55ES7100 Blinking front light and no backlight - clicking

The backlights don't always come on that way, you may need to force them on, see this fast track guide
Does your pfc voltage come up when the main to power plug is disconnected?

[jason123]

Re: Samsung UN55ES7100 Blinking front light and no backlight - clicking

Thanks R_J
The pinouts on this model are a bit different. PWR on / Off has 3.3V on it when disconnected from the main board (assuming high = on)

I connected it with a jumper to 5 volts, and that didn't make a difference (I could hear the relay on / off)

I didn't understand that last bit. I had the DMM connected across the large Cap (reading 162 VDC) and unplugged the AC cable, and the voltage started coming down.
Maybe I didn't understand: "Does your pfc voltage come up when the main to power plug is disconnected?"

[R_J]

Re: Samsung UN55ES7100 Blinking front light and no backlight - clicking

when the power supply is in standby mode, the voltage across the main cap (120vac input) will be around 160vdc, when the power supply is turned ON, the pfc circuit starts and boosts that voltage to around 380vdc
The pfc should come up with the main to power plug disconnected, the other voltages should also come up
Usually the PS_ON pin is connected to the standby voltage with a resistor and main board holds this pin low, so when the cableis removed the pullup resistor takes the PS_ON to the standby voltage, so maybe check the transistor that is connected to the ps_on pin to see if it is ok and not keeping the power supply from turning on.

[jason123]

Re: Samsung UN55ES7100 Blinking front light and no backlight - clicking

The PS_ON on the power supply, whether pulled up to 3.3, 5.1V or gnd, doesn't turn on the Backlight, and the voltage across the big caps is not changing from 162-161 V DC.

This suggests the problem is within the PS board, correct in my assumption?

[R_J]

Re: Samsung UN55ES7100 Blinking front light and no backlight - clicking

The PS_ON pin should turn on the power supply main supply and pfc only, and give you B5 and B13 volts, not the backlight, that can use a different pin/s
Have you checked the fuses FP802s & FP803s?
I see shopjimmy lists a repair kit for this board, maybe check the parts shown in there kit

[nomoresonys]

Re: Samsung UN55ES7100 Blinking front light and no backlight - clicking

So what pins did you jumper #3 and #17? on some you need to use the bu 5 v pin.

[jason123]

Re: Samsung UN55ES7100 Blinking front light and no backlight - clicking

referring to the photo here (PS labels), with the connector unplugged from main
Pin 20 is 3.3 V
Pin 18 5.14 V

No other voltages are present.
I jumpered 20 to 18 = No state change (no clicking)
connected 12 to 18 and to 20 = No change
Connected 3 to 18 = no change

In all the combinations above, B5V, or B13V never came on.

[R_J]

Re: Samsung UN55ES7100 Blinking front light and no backlight - clicking

I would'nt worry about the backlight circuit, you first need to get the B5v and B13v working.
Did you check what I asked before?

You say pin 20 is 3.3v, that is with the plug disconnected from the main, Pin 20 should have a pullup resistor connected to A5v. It then connects to another resistor to the base/gate of a transistor. That transistor may be bad and if it is the power supply will never turn on.
Locate QQ852 and check the resistance between the gate (marked in red) and ground, next to it is QQ856, it might be shorted also.

[jason123]

Re: Samsung UN55ES7100 Blinking front light and no backlight - clicking

Resistance between base & gnd is 67.6k (keeps going up slowly) high impedance on the other transistor as well. No sign of shorting

[R_J]

Re: Samsung UN55ES7100 Blinking front light and no backlight - clicking

I guess RS852 must be a high value (100k) so it drops the A5V down to 3.3V at that PS_ON pin. similar to this circuit
Does the relay still click off and on with the main disconnected?

[jason123]

Re: Samsung UN55ES7100 Blinking front light and no backlight - clicking

Yes, the Relay clicks when I short the PS_ON to GND

[R_J]

Re: Samsung UN55ES7100 Blinking front light and no backlight - clicking

Shorting the PS_ON to ground would be turning the power supply OFF and placing it in standby. When PS_ON is high does the relay only click once or keep clicking?
At this point I will assume the two fuses are ok.

[jason123]

Re: Samsung UN55ES7100 Blinking front light and no backlight - clicking

It only clicks once. When I connect the main board, and turn the TV on, in addition to the blinking, it seems that it would start to tun on, then off.. so on.

Yes, all 3 fuses on the board are OK. I checked the larger FETs and Diodes, and I don't see anything out of the ordinary (shorts)

[R_J]

Re: Samsung UN55ES7100 Blinking front light and no backlight - clicking

Now you need to find out why the B5V and B13V are not turning on. The ic that drives that circuit is under the small heatsink near CP811 cap.
Check if RM807 is ok and not open
On the hot side QS801 I believe is the VCC switch that supplies VCC to ICM801, using hot ground , check the voltage on PC8025 (opto) collector and emitter

The ICM801 might be a FSFR1700 or similar ic, it requires VCC on pin7 (~12volts) which is usually supplied by transistor QS801 and then switched by a transistor likely QM852

[jason123]

Re: Samsung UN55ES7100 Blinking front light and no backlight - clicking

RM807 reads about 0.5 ohm. Opto PC802S reads 12.9v and 13 v on the hot side pins. The other transistors seem to not be shorted. Any measurements on those is needed?

[R_J]

Re: Samsung UN55ES7100 Blinking front light and no backlight - clicking

Does icm801 have vcc on pin 7, You can check for it on JP804 or JP903 That VCC voltage is also needed to turn on the pfc section icp801s
The opto has 13 volts on e & c which indicates it is turned on, so ps_on must be working.

[jason123]

Re: Samsung UN55ES7100 Blinking front light and no backlight - clicking

JP804 has 10.7V referenced to hot gnd

[R_J]

Re: Samsung UN55ES7100 Blinking front light and no backlight - clicking

Usually once the pfc ic (icp801s) gets its VCC it should turn on and you would get the boosted voltage on the main cap
Whats the number on icp801s?

[jason123]

Re: Samsung UN55ES7100 Blinking front light and no backlight - clicking

Spc7011f