no backlight supply volts hisense ub50ec591uwt

[Diah]

Re: no backlight supply volts hisense ub50ec591uwt

what about PWM3 you didn't listed ?

[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

[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

[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

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

[Diah]

Re: no backlight supply volts hisense ub50ec591uwt

ok ive tested the leds as per your instructions ,
there are 8 leds that measure oc when i reverse the test leads on mm using diode test
so before i can test the tcon i will try to source some correct leds with the correct reverse resistance and then get back to you thanks for expert help so far

TV BL LEDs are designed by Type(size) and single or double ,,and working voltage then lumen and the last FW currents.

all these information can be checked on the led string .. in case no much info on the string label , need to solder out one defect one. to measure it

[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 ---

ok ive tested the leds as per your instructions ,
there are 8 leds that measure oc when i reverse the test leads on mm using diode test
so before i can test the tcon i will try to source some correct leds with the correct reverse resistance and then get back to you thanks for expert help so far

[Diah]

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 ---

[jimbofz]

Re: no backlight supply volts hisense ub50ec591uwt

also please upload photo on whole the back side show how the boards connected..

if your panel integrated with T-CON, the set will not working if the panel out side the set.

also did you check before when you have sound to hear with torch light can see picture on the screen ??

the t con is separate from main board and the test with torch i couldnt see any pic info

[Diah]

Re: no backlight supply volts hisense ub50ec591uwt

in the process of strip down as you sugested to examine the leds futher i will update thanks

also please upload photo on whole the back side show how the boards connected..

if your panel integrated with T-CON, the set will not working if the panel out side the set.

also did you check before when you have sound to hear with torch light can see picture on the screen ??

[jimbofz]

Re: no backlight supply volts hisense ub50ec591uwt

there are stage at the bootloader which turn the bL ON.. later we can inspect after you do the most importanr of tsting the lEDs

tear it down and put the LCD at safe place until you have the BL working... as well the screen apart from the T-CON ribbon the set working

test the LED as i told you first.. and the socket wiring too.

in the process of strip down as you sugested to examine the leds futher i will update thanks

[jimbofz]

Re: no backlight supply volts hisense ub50ec591uwt

yes these diodes have been checked
and i have a scope

[dick_barton]

Re: no backlight supply volts hisense ub50ec591uwt

Looks like the led is driven by an high frequency AC signal driven via T902 & T901 and rectified by diodes VD903 to VD906. Have you checked those diodes?

Do you have access to an oscilloscope?

[Diah]

Re: no backlight supply volts hisense ub50ec591uwt

i can open it up again to check.
but would i not get a feed voltage with strings both unplugged
on peak hold meter setting ,even for a second?

there are stage at the bootloader which turn the bL ON.. later we can inspect after you do the most importanr of tsting the lEDs

tear it down and put the LCD at safe place until you have the BL working... as well the screen apart from the T-CON ribbon the set working

test the LED as i told you first.. and the socket wiring too.

[jimbofz]

Re: no backlight supply volts hisense ub50ec591uwt

i can open it up again to check.
but would i not get a feed voltage with strings both unplugged
on peak hold meter setting ,even for a second?

[jimbofz]

Re: no backlight supply volts hisense ub50ec591uwt

i tested the led strips first with diode test to see if the volts from my meter was enough to light the leds separately then each strip was fed with 27v and all leds lit with even illumination then all the connecting leads were tested for o/c connections

[Diah]

Re: no backlight supply volts hisense ub50ec591uwt

also with DM on diode mode, if you test each one position it should lid on dimm ( depend on the batteries of the DM ) and if you put the DM probe in opposite direction it should read Zener forward current

[Diah]

Re: no backlight supply volts hisense ub50ec591uwt

very interesting is this zener on the psu board or inside with the led string ? as i didnt see any diode on the led strips?

each LED on the BL string built in Zener Diode for forward current

[jimbofz]

Re: no backlight supply volts hisense ub50ec591uwt

very interesting is this zener on the psu board or inside with the led string ? as i didnt see any diode on the led strips?

[Diah]

Re: no backlight supply volts hisense ub50ec591uwt

i guess you have OPEN Zener Diode on LED , with test of just lighting up didn't approve the zener condition .. it should tested with DM on diode mode or you have soldering point on one of the socket of BL string this why 3V on LED BL socket low.