Samsung LED LCD UE32C5100 no power no stand-by

[Tdiamarelo]

Hello!

Just got a Samsung LCD 32 inches completely dead.
No stand by light.

At the main connector from the PSU to the Main board (Pin 16) i get my STBY_5.2V, all the rest is at 0V.

I could not find the service manual for the UE32C5100 but found one whit the same chassis (N92A)
Could you confirm that this is the correct chassis number?

After reading a little from the schematics i noticed some fuses at the connector from the main board. (didn't had the time to check them).

My question now is on my main board schematic i do not have the same pin-out description... so not sure if i have the correct schematics... is my STBY_5.2V on PSU side the A5V_PW on the main board side?

How can i simulate a main board OK start signal on the PSU (board BN44-00351B) to see if my power supply is working fine as i think it is.

I know... i have a lot of questions... really need to fix this set... it has cost me 50$ so my wife is going to kill me if i don't get it running!

[budm]

Re: Samsung LED LCD UE32C5100 no power no stand-by

1) You can start by providing the pictures of the whole backside of the TV showing all the boards.
2) Remove the cable between power supply board and the main board then power up the power supply board and see if the backlights will come on and stay on as long as the power is applied to the power supply board, also take the Voltage readings of the power supply connector. The connector has label for each pin so you need to report the reading in this format:
Pin1 XYZ = xx Volts

[Robinsosa]

Re: Samsung LED LCD UE32C5100 no power no stand-by

PS circuit diagram for BN44-0351B

[Tdiamarelo]

Re: Samsung LED LCD UE32C5100 no power no stand-by

Thanks for the reply, i will take some pictures tonight when i arrive home.

BUDM - If i remove the connector i only have the 5.2V stand-by voltage. All the other are at 0V because it is in sleep mode.

I need to know how to force start the PSU, so it thinks that the main board is sending the OK or Power ON signal (because the set is completely dead and if i press the power button nothing happens so sure no back lights), and then measure the voltages.
I think it is done whit a 1K resistor and pull to ground one of the pins or to the 5.2V... not sure how this one is.

RABINSOSA - Thank for the schematics... that one i already have... need one for the main board. Do you have one for this set?

Thanks for the help!

[nomoresonys]

Re: Samsung LED LCD UE32C5100 no power no stand-by

What's this "sleep mode"?? Bud is describing the powerboard self test, when you unhook the cable the backlights will come on and stay on IF the powerboard and backlight circuit are working correctly.

[Tdiamarelo]

Re: Samsung LED LCD UE32C5100 no power no stand-by

Nothing happens when i unplug the cable.

[Tdiamarelo]

Re: Samsung LED LCD UE32C5100 no power no stand-by

What's this "sleep mode"?? Bud is describing the powerboard self test, when you unhook the cable the backlights will come on and stay on IF the powerboard and backlight circuit are working correctly.

What i mean under sleep mode is when the TV is in Stand-by your power supply is almost completely shut down, you have your primary working but secondary is waiting (sleeping) until the control board says Wake up when you press the power button.

[nomoresonys]

Re: Samsung LED LCD UE32C5100 no power no stand-by

Samsung have pullup resistors, that's why the backlights should come on with cable unplugged, looks like your problem is with powerboard or backlight circuit, could also be a mainboard issue but you need to get the powerboard or backlight circuit fixed first.

[nomoresonys]

Re: Samsung LED LCD UE32C5100 no power no stand-by

Maybe start with checking all the diodes on powerboard, meter on diode mode, check then reverse meter probes, one way should read .2 ~.7 or so and OL when probes reversed, check with tv UNPLUGGED from power.

[Tdiamarelo]

Re: Samsung LED LCD UE32C5100 no power no stand-by

If they have pullup resistors then i need to feed trough a 1K resistor, 5V to the pin 18 (PW_ON/OFF) to start the PSU?

All diodes seem ok, they only lead one way... OL in the blocking sense. I have around 330V on the 2 long caps. The small ones near the cable plug i only have 5.2V in some of them. All the other 0V and the ones near the LED panel output also 0V.

On the ICS801 (STR-W6052S) pin 4 only gets 10.2V, if I'm not mistaken it should only work when at least 14.3V are applied.
If i remove the cable to the main board the voltage on the pin goes down to 0V. If i reconnect it goes back to 10.2V
Pin 1 around 370V
All other pins 0V
Sure there is a problem right here don't know what could be...
Maybe this helps to troubleshoot better this issue.

[Tdiamarelo]

Re: Samsung LED LCD UE32C5100 no power no stand-by

Here are the boards pictures

[budm]

Re: Samsung LED LCD UE32C5100 no power no stand-by

Looking at the schematic, the pull-up resistor for the PS-ON is not installed so you need to use the 1K resistor on PS-ON and STBY5V to force on the power supply and see what will happen. The BLU has pull-up resistor according according to the schematic.

[will62]

Re: Samsung LED LCD UE32C5100 no power no stand-by

is my STBY_5.2V on PSU side the A5V_PW on the main board side?

Yes. See p2 of the attached. The pull-up for pw_on is on the main board (r210).
Also on p2, you'll find all the ic's that generate the 1.1V, 1.8V, 2.5V & 3.3V. You need to make sure that those are putting out the correct voltages for your main ic.

[Tdiamarelo]

Re: Samsung LED LCD UE32C5100 no power no stand-by

Thanks. Will work on it tomorrow. Will try the pullup resistor with cable disconnected to the main board to check the PSU and then i'm checking if all the IC get the 5v because there is no other voltage on the board for now.

[Tdiamarelo]

Re: Samsung LED LCD UE32C5100 no power no stand-by

Hello folks
Today I did a little more research and found out following...
Whit the pullup resistor nothing changes at the connector to the main board but inside the PSU it has changed.

If you look at page 1 from power supply's schematics on the cold side you have the 5.2V from standby and on top of this you have the 12v and 5.3v that should go to the main board. I took some measurements and found out that :
I get 20.2V after diode DM820
18.2V after diode DM853
And 4.8V after diode DM851.
So my hot side I think it's working ok when I put the pullup resistor.

Now the problem I found is that I get 18.2V on pin 5,6,7 and 8 and 29V on the gate (pin 4) from IC QM820 but no output on pins 1,2 or 3.
If I read the schematics correctly that means that I get nothing on gate pin from IC QM821 and so no 5.3V on PSU.

My question here... how can I test if my QM820 is working?
Whit 18.2V on the drive and 29V at the gate should I have an output?

Another funny thing whit black probe on chassis ground and another on on the resistor RM820 at one side i get 20.2V and on the other side 0V. Is there another ground?

[R_J]

Re: Samsung LED LCD UE32C5100 no power no stand-by

You say you have 29v on one side of RM821 (QM820-pin4) and 0 on the other side (RM820 at one side i get 20.2V and on the other side 0V) These voltages don't make sense. Is RM821 open? Where can 29 volts come from?

Is the power supply disconnected from the main board and do you have a 1K resistor between STBY_5.3V and Power_ON/OFF

[budm]

Re: Samsung LED LCD UE32C5100 no power no stand-by

you say you have 29v on one side of rm821 (qm820-pin4) and 0 on the other side (rm820 at one side i get 20.2v and on the other side 0v) these voltages don't make sense. Is rm821 open? Where can 29 volts come from?

Is the power supply disconnected from the main board and do you have a 1k resistor between stby_5.3v and power_on/off

+10

[Tdiamarelo]

Re: Samsung LED LCD UE32C5100 no power no stand-by

I explain again...
Whit the pullup resistor in place i get:
On the QM820, 18.2V on the (D) pins (number 5,6,7,8) and 29V on the (G) pin 4.
The 3 (S) pins i don't have any output.
On the QM821, 4.8V on the (D) pins (number 5,6,7,8). No other voltage.

If i remove the pullup resistor my 29V from pin 4 from QM820 go to 0V.

[Tdiamarelo]

Re: Samsung LED LCD UE32C5100 no power no stand-by

My RM821 reads 22 ohm whit multi-meter.
How can i test my QM820 since i don't have any voltage on the (S) pins.
If I'm not mistaken the output (S pins) should be generating the 12V I'm missing on the board.

[Tdiamarelo]

Re: Samsung LED LCD UE32C5100 no power no stand-by

OK so to be easier for everybody to understand i inserted in the schematics the exact point where, and the voltage that i measured.