no backlight supply volts hisense ub50ec591uwt

[Diah]

Re: no backlight supply volts hisense ub50ec591uwt

did you test voltage at each led connector on the power board with plugs connected whilst powering the set on ?

what kind of sense it make this test when OP stated he found 8 LEDs are OPEN ????

[petehall347]

Re: no backlight supply volts hisense ub50ec591uwt

what kind of sense it make this test when OP stated he found 8 LEDs are OPEN ????

i read this ...https://www.badcaps.net/forum/showpo...02&postcount=9

[jimbofz]

Re: no backlight supply volts hisense ub50ec591uwt

open the metal shield of the T_CON post very clear close photo of it... also you have on it SMT fuse test it black probe on chassis if you have 12V. on both side of the fuse.
BTW:
if you confirmed there are 12V on both side of the T_CON fuse.. please put every things in place and turn on the TV, black probe on chassis and read all the voltage as they are listed over here
PWM2 --
SW ---
12V ---
STB ---
16V ---
3DS ---
3DE ---
PWM3 ---

i have tested and replaced all leds that gave oc reading on foreward current test now they will all light separately with external supply.
the 12v feed to tcon is good on both sides of fuse .
the psu o/p plug has 10 pins ,not as shown printed on the side of the board next to the plug which is for a 15 pin version of the panel
i am posting a pic of the voltages measured on the plug
basically its ;pwm2 2.9v switching
sw 3.5v switching
sby 3.8v switching
12v supply not switching
16v supply 19.2 not switching
the only thing thats bothering me is the original leds need a higher voltage to light compared to the ones ive replaced which will light with my dmm on diode test
still only 3 volts backlight feed

[Diah]

Re: no backlight supply volts hisense ub50ec591uwt

what about PWM3 you didn't listed ?

[jimbofz]

Re: no backlight supply volts hisense ub50ec591uwt

i know ,it isnt used on my 10 pin version of the psu panel

[Diah]

Re: no backlight supply volts hisense ub50ec591uwt

this is strange.. this TV had story before its come under your hand.. who knows if the PWB belong to it ???

[Diah]

Re: no backlight supply volts hisense ub50ec591uwt

disconnected the main boards totally from Power boards , make jumper Resistor 1K between SW ( yelow) and STB, on the PWB and plug it in wall socket and read the voltage again

[dick_barton]

Re: no backlight supply volts hisense ub50ec591uwt

While you are doing that test could you also check Pin16 of the LX2901. Votage should be a regulated 5.25V

[jimbofz]

Re: no backlight supply volts hisense ub50ec591uwt

i was told it just failed and the backlights all looked untouched ,if the psu was the wrong one you would assume that the main board would have a plug with missing lead also the main board does not have any spare sockets for any other plug ,so from this i assume its the correct psu .
the two pins with the 20v on, are joined on the print of the psu ,and i wonder why its not 16v as shown on psu , the 12v is ok shown as 12 v on psu.
if i unplug the main board and fit jumper between SW and STB surely the psu cant start up as both these pins read 0v at switch on and only recieve volts to turn on from main board ? or am i missing something

[Diah]

Re: no backlight supply volts hisense ub50ec591uwt

STB always read the same voltage as its provided by PSU
SW 3.5V are signal provided from MB to turn on the PSU 12 16V, the jumper will replace the MB action

[jimbofz]

Re: no backlight supply volts hisense ub50ec591uwt

While you are doing that test could you also check Pin16 of the LX2901. Votage should be a regulated 5.25V

pin 1 12v
pin 2 2.4v
pin16 low only .9v

[jimbofz]

Re: no backlight supply volts hisense ub50ec591uwt

STB always read the same voltage as its provided by PSU
SW 3.5V are signal provided from MB to turn on the PSU 12 16V, the jumper will replace the MB action

thanks for explaining ,fitted jumper 1k
16v ok 12v ok , sadly still no bl volts

[Diah]

Re: no backlight supply volts hisense ub50ec591uwt

16 V read 16 ?
remember you told us it was 20 at STB and 19 at ON ?

[dick_barton]

Re: no backlight supply volts hisense ub50ec591uwt

Pin 1, VCC can accept a voltage of 10V to 27V so the supply to the IC is fine.

Pin 2, Enable input is also fine at 2.4V so the IC is enabled.

Pin 16 is a 5.25V regulated supply internally generated from Vin and is the supply voltage for the circuitry inside the IC.

I would say that it looks like either the IC is faulty or any capacitor connected to pin 16 needs to be checked.

[Diah]

Re: no backlight supply volts hisense ub50ec591uwt

keep the 1K jumper in place and make another 1K jumper between STB and PWM2 the BL socket should read voltage and may the BL come on.

[jimbofz]

Re: no backlight supply volts hisense ub50ec591uwt

Pin 1, VCC can accept a voltage of 10V to 27V so the supply to the IC is fine.

Pin 2, Enable input is also fine at 2.4V so the IC is enabled.

Pin 16 is a 5.25V regulated supply internally generated from Vin and is the supply voltage for the circuitry inside the IC.

I would say that it looks like either the IC is faulty or any capacitor connected to pin 16 needs to be checked.

i agree the cap on pin 16 measures 160 ohm to deck ,i unsoldered it and it declared its innocence the other 3 resistors connected to pin 16 are fine so it looks like faulty ic
this tv has two led strings im wondering if there resistances at switch on are compared within this chip it would then fail to produce this voltage on pin 16 although all leds test fine perhaps theres a difference in the replacements i have fitted compared to the originals?

[jimbofz]

Re: no backlight supply volts hisense ub50ec591uwt

keep the 1K jumper in place and make another 1K jumper between STB and PWM2 the BL socket should read voltage and may the BL come on.

tried with two 1k jumpers
same result no bl volts

[jimbofz]

Re: no backlight supply volts hisense ub50ec591uwt

16 V read 16 ?
remember you told us it was 20 at STB and 19 at ON ?

sorry 16v reads 20v in sby and 19v when on my mistake

[Diah]

Re: no backlight supply volts hisense ub50ec591uwt

show us clear photo of the back side of the PWB

[jimbofz]

Re: no backlight supply volts hisense ub50ec591uwt

ok posting now