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Old 12-04-2017, 01:02 PM   #1
fejlong
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Default LED TV Samsung UE32D5520 PSU 2 second to black

Hi everyone,

I'm here because I have a dead end finding the fault on a LED TV Samsung UE32D5520
It turns on, but goes black after 2 seconds and the red led in front blinks twice, after this it restarts again, but does not restart always. Sometimes remains in the off state.

The power supply wich I am suspecting makes a changing buzzing sound, the source of the buzz is comming aprox from the middle of the power board where the transformer is located near the 68uf 200V cap.

Output voltages are 12.6 insted of 13.0 and 5.4 insted of 5.0 these are for the logic board.
LED screen light voltage is unstable between 124V and 135V. I don't know wich would be correct for this one. I don't have a service manual for it.

I suspect that because of this unstable voltage the protection circuit comes in and shuts the power off.

Atteched are 2 pictures of the board, back and front.

Can any one direct me in the right direction to repair this board?
Best regards,
Dawe
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File Type: jpg P_20171203_222222.jpg (1.00 MB, 39 views)
File Type: jpg P_20171203_222230.jpg (726.6 KB, 40 views)
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Old 12-04-2017, 02:42 PM   #2
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Default Re: LED TV Samsung UE32D5520 PSU 2 second to black

Inspect and re-solder ALL the pins of the transformers and all the legs of the devices there attached to the heatsinks because board is known for cold solder joints.
Your pictures are not in focus.
What is the board P/N? BN44-?????
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Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956

Voltage Regulator (LDO) testing:
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Inverter testing using old CFL:
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TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
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Old 12-04-2017, 05:32 PM   #3
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Default Re: LED TV Samsung UE32D5520 PSU 2 second to black

"LED screen light voltage is unstable between 124V and 135V"
Is that with reference to chassis GND?
So far it looks like some of the LEDs are shorted out.
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Old 12-05-2017, 12:07 PM   #4
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Default Re: LED TV Samsung UE32D5520 PSU 2 second to black

I am sorry, I made those blurry pictures with my phone,
here are some attached made with a camera,

the board P/N: BN44-00460A

You will see solder marks on the 68uF capacitor legs, I did re-solder them.

I will re-solder all the pins you suggested and will post the results here.
Thanks
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File Type: jpg _DSC2799.jpg (830.2 KB, 24 views)

Last edited by fejlong; 12-05-2017 at 12:11 PM..
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Old 12-05-2017, 12:34 PM   #5
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Default Re: LED TV Samsung UE32D5520 PSU 2 second to black

Quote:
Originally Posted by budm View Post
"LED screen light voltage is unstable between 124V and 135V"
Is that with reference to chassis GND?
So far it looks like some of the LEDs are shorted out.
Actually its not LED screen light voltage, I tought it was. It is voltage on the 68uF cap

I did removed all solder joints and re-soldered with fresh solder the transformer and the legs of the devices under heatsinks. No change, still buzzing

Last edited by fejlong; 12-05-2017 at 12:44 PM..
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Old 12-05-2017, 02:42 PM   #6
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Default Re: LED TV Samsung UE32D5520 PSU 2 second to black

OK, You need to test the DC Voltage on the CNL802
Pin 1: Top 1 + (The Anode of the first LED string)
Pin 3: Top 1 - (The Cathode of the first LED string)
Pin 5: Top 2+ (The Anode of the second LED string)
Pin 7: Top 2- (The Cathode of the second LED string)
1) You will leave the Black probe on the chassis, Red probe on the TOP1 + then keep an eye on the meter when turn on the TV and record how high the Voltage goes up to and then wait 5 seconds to see how low it goes down to. Turn off the TV.
2) Repeat the same procedures for the other 3 pins.
It is VERY IMPORTANT that you follow the instructions.
BTW: You are getting the reading of 124~135V on that main filter cap because you use the wrong GND for the meter, that cap is in the primary side circuit so the negative leg of the main filter cap will be your GND ref. for your meter, not the chassis.
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Old 12-06-2017, 03:14 AM   #7
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Default Re: LED TV Samsung UE32D5520 PSU 2 second to black

uploaded pdf services manual samsung_ue32_37_40_46eh5xxx_eh4x may help you
if you disconnect main power supply connector to mainboard the backlight must be active and turning on. please check.
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Old 12-08-2017, 09:04 AM   #8
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Default Re: LED TV Samsung UE32D5520 PSU 2 second to black

Quote:
Originally Posted by boyebaran View Post
uploaded pdf services manual samsung_ue32_37_40_46eh5xxx_eh4x may help you
if you disconnect main power supply connector to mainboard the backlight must be active and turning on. please check.
I can't see this model of PSU in the schematic provided.

It doe's not turn on
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Old 12-08-2017, 09:21 AM   #9
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Default Re: LED TV Samsung UE32D5520 PSU 2 second to black

Dear budm,

The thing is, that I suspected the 68uf cap, so I desoldered it and used another 68up cap at 400V wich I had at hand. From that moment it won't turn on anymore, not even for 2 seconds. So, I cannot measure voltage on CNL802(it shows high impedance). This was before re-soldering the legs of the transformer. It was the same fenomenom showing with the 68uf 400V cap as well.

The voltage of 124-135V is on the legs of this 68uf 200V cap, I soldered it back. I found a suitable schematic wich confirms that this voltage is incorect. It should be 145V not less, not more. Schematic attached.

Voltage at cap C9110(8.2uf 400V) is the same as at CM852(68uf 200V), I guess IC9101 is definetely not working. Is the low voltage of 125-135V the cause?
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File Type: pdf UA32D4000NW_PD32A0-BSM.pdf (1.08 MB, 47 views)

Last edited by fejlong; 12-08-2017 at 09:28 AM..
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Old 12-08-2017, 03:14 PM   #10
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Default Re: LED TV Samsung UE32D5520 PSU 2 second to black

Your power supply board is BN44-00460A as printed on your board:
https://www.badcaps.net/forum/attach...7&d=1512497228

The 'UA32D4000NW_PD32A0-BSM' schematic is the reverse engineering drawing of the BN44-00421A.

So at this point you still have 125~135VDC on the cap?
The IC9101 will turn on the boost converter circuit to boost the 145V per the schematic (in you case the 125-135) to 195V (in your case the LED voltage is printed on your board so look at the print to see see what it says). The boosted Voltage is fed to the CNL802 pin 1+.
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Old 12-08-2017, 06:23 PM   #11
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Default Re: LED TV Samsung UE32D5520 PSU 2 second to black

Yes, I still have 125-135V on the cap, and the same voltage on connector CNL802.
I found the printing on the board, it says: LED driver Output:148V/290mA(CNL802)
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Old 12-08-2017, 08:32 PM   #12
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Default Re: LED TV Samsung UE32D5520 PSU 2 second to black

OK, so based on your post #1:"It turns on, but goes black after 2 seconds" The backlights backlights did come on for seconds, that means it went into shutdown after coming on so that means the booted converter did kick on to give higher output Voltage to light up the LED string but then kick back off due to the protection may have been detected.
So you need to do the test in my post #6 which you did not do, correct?

Last edited by budm; 12-08-2017 at 08:33 PM..
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Old 12-09-2017, 02:03 PM   #13
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Default Re: LED TV Samsung UE32D5520 PSU 2 second to black

No, it won't turn on anymore, see post #9
I did measure the voltage on CNL802, same changing voltage 125-136V
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Old 12-09-2017, 05:36 PM   #14
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Default Re: LED TV Samsung UE32D5520 PSU 2 second to black

"but goes black after 2 seconds"
Well in post 1 at the beginning the boost converter was working otherwise there is no way you had the backlights come on for 2 seconds and then goes off after the protection shutdown kick in.
"I did measure the voltage on CNL802, same changing voltage 125-136V" so you dis the probes in place and watch the meter when turn on the TV and did not see it jumps up above 136V at all, it will happen very fast that is why you have to keep an eye on the meter when turn on the TV, correct? If that is the case you need to get new board at this point because I do not know EXACTLY what you did that causes it not to have the same symptom as in post 1 any more.

Last edited by budm; 12-09-2017 at 05:37 PM..
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Old 12-10-2017, 04:46 AM   #15
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Default Re: LED TV Samsung UE32D5520 PSU 2 second to black

in post 9 you changed one capacitor now it wont turn on at all can you put the old capacitor back in as your replacement maybe faulty, also check around that area for any possible solder bridges/bad soldered joints.
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Old 01-15-2020, 08:24 AM   #16
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Default Re: LED TV Samsung UE32D5520 PSU 2 second to black

Quote:
Originally Posted by budm View Post
OK, You need to test the DC Voltage on the CNL802
Pin 1: Top 1 + (The Anode of the first LED string)
Pin 3: Top 1 - (The Cathode of the first LED string)
Pin 5: Top 2+ (The Anode of the second LED string)
Pin 7: Top 2- (The Cathode of the second LED string)
1) You will leave the Black probe on the chassis, Red probe on the TOP1 + then keep an eye on the meter when turn on the TV and record how high the Voltage goes up to and then wait 5 seconds to see how low it goes down to. Turn off the TV.
2) Repeat the same procedures for the other 3 pins.
It is VERY IMPORTANT that you follow the instructions.
BTW: You are getting the reading of 124~135V on that main filter cap because you use the wrong GND for the meter, that cap is in the primary side circuit so the negative leg of the main filter cap will be your GND ref. for your meter, not the chassis.
I have a Samsung LTJ320HN01-V TV with a BB44-00460A power supply which doesn't have backlight. On beaming a torchlight, l can see the menu. First the video went off, now even audio is not coming.
The voltage between chassis and TOP1+ is between 110 and 160V. Between chassis and other leads on CNL802 is zero. What could be the problem?
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