no backlight supply volts hisense ub50ec591uwt

[Diah]

Re: no backlight supply volts hisense ub50ec591uwt

ud 901/902 check out ok by comparison with similar board using same fets
the psu pin STB has no volts on it until main board is plugged in so links with 1k resistors wont start

i am confused .. are you repairing now 2 power boards at same time ?? how it come STB voltage not exist only if MB connected ??? sorry man i cant follow your points.. it make real headage

[jimbofz]

Re: no backlight supply volts hisense ub50ec591uwt

ud 901/902 check out ok by comparison with similar board using same fets
the psu pin STB has no volts on it until main board is plugged in so links with 1k resistors wont start

[Diah]

Re: no backlight supply volts hisense ub50ec591uwt

when you do 2 jumper 1K ... the second one between STB to PWM2 ( orange) how much the volts read on the orange pin after the 1K ?? and before on STB pin. and are you sure no V on BL socket ??( you can disconnect the LED socket and measure )

BTW: i think you have over clock on the hot area.. this why the 16V show 20 ... UD901 &902 need to test them after the free them from the boards

[jimbofz]

Re: no backlight supply volts hisense ub50ec591uwt

show us clear photo of the back side of the PWB

heres pics of print side psu in pic 3 you can see that the last 5 pins are not used

[jimbofz]

Re: no backlight supply volts hisense ub50ec591uwt

ok posting now

[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

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

[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

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?

[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.

[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

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

[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

[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

[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

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

[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

[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

[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 ???

[jimbofz]

Re: no backlight supply volts hisense ub50ec591uwt

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