Samsung UE32D5520 buzzing PSU, no picture

[fejlong]

Hello everyone,

Got this nice monitor for a while now, I struggle to make it work again, and I read that here might be some very nice people that could point me in the right direction to repair it.

Under power the backlight won't come on, a buzzing sound starts and then fades away after a few seconds, then it starts again. Can't tell exactly from where, but I think it's the transformer in the middle of the power supply board, or around it.

The red LED in the front of the tv flashes five times, then 2-3secs off. Probably this is an error code, cant find a service manual to look it up. Are some samsungs simillar in opration, ones error code will be the same as other model's error code?

I am suspecting that the power board is faulty, but I might be worng.
If the mainboard is disconected from the power board the intermittent buzzing sound turns into a more finer continueos buzzing. The cable between the LED board and power supply board still connected at this point. Voltages at CNM803 are 12.83V(13V) and 5.32V(5V). There are two main capacitors on this power board voltages are 347V is this high enough?

any help would be apreciated,
Thanks

[budm]

Re: Samsung UE32D5520 buzzing PSU, no picture

Pictures are too dark for me to read anything on the board.
Please provide straight shots pictures of the whole top and bottom side of the power supply board.
What is the P/N of the power supply board? BN44-?????

[fejlong]

Re: Samsung UE32D5520 buzzing PSU, no picture

Board is BN44-00460A

These are the best pictures I can take with maximum light that I have.

Thanks

[R_J]

Re: Samsung UE32D5520 buzzing PSU, no picture

You could try measuring the voltage on CNL802 since the problem is likely with the backlight, Check it on TOP1+ when you first turn on the tv. It should be around 148vdc

[fejlong]

Re: Samsung UE32D5520 buzzing PSU, no picture

on CNL802 reference to ground
1.TOP1+ 118V,
2. N.C.
3. TOP1- 67V,
4. N.C.
5. TOP2+ 67V,
6. N.C.
7.TOP2- 18V
8. N.C.
9. IF2
10. IF1

[budm]

Re: Samsung UE32D5520 buzzing PSU, no picture

Disconnect the LED connector form the power supply board, leave the meter connected to TOP1+ and chassis GND then turn on the TV to see what Voltage reading will be.

[fejlong]

Re: Samsung UE32D5520 buzzing PSU, no picture

With the LED connector disconnected on TOP1+ the same voltage can be measured. Not on the rest of the pins though.

The TV cannot be turned on. It is digital touch buttons and doesn't seem to respond to them.
As the cord is plugged in, red LED blinks a few times and goes out.

[dick_barton]

Re: Samsung UE32D5520 buzzing PSU, no picture

Led voltage is givenon the power supply board as 148V @ 290mA.

What dc voltage do you have beween the two legs of CP814S. Be careful that your meter leads do not slip off the capacitor legs when taking the measurement.

What is the voltage at CNL802 PIn1 at switch on. It may go higher than 118V then drop quickly. The min/max function on your meter would be useful for catching a spike in voltage.

[fejlong]

Re: Samsung UE32D5520 buzzing PSU, no picture

DC voltage on CP814S is 347V

Voltage on CNL802 is around 104V at start-up and goes up to 118 in about two seconds. It is not higher than 118V, tried multiple multimeters, but with one of them, a fluke 113, the board behaves differently when connected to ground and pin 1 on CNL802. The difference is in the buzzing that becomes continuous and the fluke measures around 73V at this stage. The red LED blinks twice, pause, and repeats.

[dick_barton]

Re: Samsung UE32D5520 buzzing PSU, no picture

I would have expected the voltage across CP814S to be closer to 380v - 390V and could explain why the led voltage does not boost to 157V.

What dc voltage do you have across the legs of CM852

What dc voltage do you have on Pin1 of IC9101 when you try bringing the set out of standby?

[fejlong]

Re: Samsung UE32D5520 buzzing PSU, no picture

Voltage on CM852 is same 118V

I am manually trying to power up the board from CMN803 power on pin. Before power on pin 1 of IC9101 has 12.7V. After power on this voltage drops to almost zero, a few millivolts.

Also measured voltage on CP814S before and after power on and the voltage drops slightly 2-3V

Can these two capacitors be faulty, CP814S and CP815S ? They are connected in parallel

Thanks

[dick_barton]

Re: Samsung UE32D5520 buzzing PSU, no picture

CM852 could well be OK. Under the 200V rating of the capacitor.

Pin 1 of IC9101 has 12.7V which is what would be expected but drops towards 0V when power applied. This does not appear to be correct. I would expect it to be 0V when the set is in standby and 12.7V when out of standby ie switched on. Can you recheck.

What voltages do you have on the pins of CNM803 in standby and when out of standby.

[fejlong]

Re: Samsung UE32D5520 buzzing PSU, no picture

I re-checked and I confirm, standby 12.7V, power on drops close to 0V

[dick_barton]

Re: Samsung UE32D5520 buzzing PSU, no picture

I re-checked and I confirm, standby 12.7V, power on drops close to 0V

So you are confirming that Pin 1 of SEM5025 (IC9101) voltage drops from 12.7V to 0V when you come out of standby ie turn on the set.

[fejlong]

Re: Samsung UE32D5520 buzzing PSU, no picture

Yes

[dick_barton]

Re: Samsung UE32D5520 buzzing PSU, no picture

The 13.1V feed to Pin 1 of IC9101 is fed from Q9104 which is switched on/off by BLU_ON
Can you check the voltages at the connector as in post #12

[fejlong]

Re: Samsung UE32D5520 buzzing PSU, no picture

No voltage on BLU_ON at connector if this is you question

[dick_barton]

Re: Samsung UE32D5520 buzzing PSU, no picture

BLU_ON should go from 0V towards 5V when the TV is turned on out of standby.

[fejlong]

Re: Samsung UE32D5520 buzzing PSU, no picture

I understand. So, if cord is plugged in(nothing else), 5V should be present and not 12.7V, right? But 12.7V is also present. Normally, if pin Power On/Off on connector CMN803
is connected to 5V 12.7 should come alive, right?

[dick_barton]

Re: Samsung UE32D5520 buzzing PSU, no picture

Disconnect the mainboard from the power supply and connect the 5V to PS_ON which is Pin 14 of CNM803 using a 1Kohm resistor. That should bring up all the supplies and the backlights should also come on.
Can you confirm Vamp, A5V, B5V, B13V are all correct and that you have 12V on Pin 1 of IC9101