Samsung le40r87bdx/xeu No back light has sound

[thosesamsungstho]

Here is the story so far Samsung Le40r87bdx/xeu with Psu board BNN00165A turns on has no back lights makes chime stays on when plugged into a dvd player a picture can be seen with a light and has sound some caps have been upgraded to 25v (previous owners must of had it repaired)

Voltages are
power on/off (when on) 1.97v
standby 5.2v (5.2v)
12v (12v)
pin 13-16. 5.4v(5.4v)
pin 19 13v (13v)
pin 21-22 = 13v (13v)

i checked the voltages going to the inverter

Vcc_12v is reading 7.65v
fb 0v
gnd 0v
nc 0v
LD 6.2v

when main board is disconnected from Power there is no backlight.

Any advise would be greatly appreciated.

[budm]

Re: Samsung le40r87bdx/xeu No back light has sound

We need good clear pictures of the backside of the TV showing how all the boards are connected together.
There should be more pins on the inverter board for the BL-ON and DIM.

'Vcc_12v is reading 7.65v' This one is BAD, it should be 12V for the protection circuit on the inverter board to function.

'LD 6.2v' Bad.

BTW, the power supply board should be BN44-00165A.
You look through these threads:
https://www.badcaps.net/forum/search...archid=6939828

[thosesamsungstho]

Re: Samsung le40r87bdx/xeu No back light has sound

i have added pictures as requested i believe this model has the pull up which should allow the backlight to come on when main board is unplugged from power which it doesnt.

[ReeceyBurger123]

Re: Samsung le40r87bdx/xeu No back light has sound

Common issue is broken solder joints on the inveter transformer on the psu.

[budm]

Re: Samsung le40r87bdx/xeu No back light has sound

i have added pictures as requested i believe this model has the pull up which should allow the backlight to come on when main board is unplugged from power which it doesnt.

The BN44-00165A does not have pull-up resistor so the power supply will not come up when running by itself.
You need to get the VCC-12V working first, you need to check the DC input to the IC UI809 78M12T to see if you have 12~13V on the input pin, more likely to be bad IC like in the thread's link below. Verify if it is 78M12T or not.
https://www.badcaps.net/forum/showth...ighlight=UI809

[thosesamsungstho]

Re: Samsung le40r87bdx/xeu No back light has sound

Thanks for the responses regarding this set it is all greatly appreciated i finally have the tv infront of me i checked the ic mentioned and its output was 3v i changed it with an exact match and no change. I took the power supply board out as soon as it arrived and it would seem it has been butchered.
(previous readings were from a friend who collected the tv for me)

I have seen a power supply board for £15 (from a trusted supplier) so that is the route i will take im just hoping that i dont get / already have eeprom corruption as this set refuses to enter service menu and just has the "buffer image merge ok" message.

sorry it wasnt an exciting ending but this board has hidden horrors.

[budm]

Re: Samsung le40r87bdx/xeu No back light has sound

The question is what is the input Voltage to that regulator, beside you indicated that you have VCC_12V of 7.6VDC not 3V, are you sure you measure the right IC?