Toshiba 19BL502B replaced diode worked, now not working

[ReeceyBurger123]

Re: Toshiba 19BL502B replaced diode worked, now not working

You appear to have an inverter fault. Will be interested in what other's think.
I suspect that when the voltage was rising to 33V it may well have damaged some of the components / IC's on that circuit board by going over voltage.

+1 or could of been the diodes shorting which killed the Led driver.

[David-OLW]

Re: Toshiba 19BL502B replaced diode worked, now not working

Which Board has the LED Driver and inverter on then?. Where are the connections to the LED's? the main board only has a ribbon type cable from it.

Thanks David.

[budm]

Re: Toshiba 19BL502B replaced diode worked, now not working

https://www.badcaps.net/forum/attach...1&d=1484649140
Small green board on the top right is the LED driver board, this not CCFL backlights system so there is no Inverter board.

[dick_barton]

Re: Toshiba 19BL502B replaced diode worked, now not working

+1 Stand corrected.
So possible led driver board or led fault.

[dick_barton]

Re: Toshiba 19BL502B replaced diode worked, now not working

There's a fuse marked in red box which would be worth checking. Also check all the 0 ohms resistors.

[vinceroger69]

Re: Toshiba 19BL502B replaced diode worked, now not working

for some reason i thought this was a ccfl set too but as the others say check the fuse and the zero ohm resistors then we can advise further

[budm]

Re: Toshiba 19BL502B replaced diode worked, now not working

Since that LED driver has boost converter, so check the DC in at the fuse and DC out to the LED when BL-ON is present.

[vinceroger69]

Re: Toshiba 19BL502B replaced diode worked, now not working

in post 14 bl on voltage 0.23v shouldnt that be higher? is it the led driver board that turns this command on higher voltage?

[David-OLW]

Re: Toshiba 19BL502B replaced diode worked, now not working

Since that LED driver has boost converter, so check the DC in at the fuse and DC out to the LED when BL-ON is present.

Many Thanks for your help.

I have 27.2 volts both sides of the fuse. Have checked all zero resistors with multi meter and have continuity across them.

David

[budm]

Re: Toshiba 19BL502B replaced diode worked, now not working

in post 14 bl on voltage 0.23v shouldnt that be higher? is it the led driver board that turns this command on higher voltage?

The LED driver circuit needs the BL-ON signal to turn on the Boost converter circuit.
That Voltage should toggle HIGH when TV is turned ON, I expect >2.5VDC if it is active high to turn on the circuit.

[vinceroger69]

Re: Toshiba 19BL502B replaced diode worked, now not working

when i asked him to test it in post 14 thats the voltage he got with the set turned on hence i thought it maybe a mainboard issue?

[David-OLW]

Re: Toshiba 19BL502B replaced diode worked, now not working

The LED driver circuit needs the BL-ON signal to turn on the Boost converter circuit.
That Voltage should toggle HIGH when TV is turned ON, I expect >2.5VDC if it is active high to turn on the circuit.

Pin 3 BKL_ON/Off when ON is 3.04 volts

Pin 4 PWM_DIM when ON is 0.23 volts

David

[vinceroger69]

Re: Toshiba 19BL502B replaced diode worked, now not working

sorry i got messed up with pin numbers so that voltage is fine , not sure though what the pwm-dim should read?

[budm]

Re: Toshiba 19BL502B replaced diode worked, now not working

Pin 3 BKL_ON/Off when ON is 3.04 volts

Pin 4 PWM_DIM when ON is 0.23 volts

David

I expect the Dimming control line to be higher than that.
BL-ON is OK @3.04V.
Put the black probe on the chassis, red probe on the DIM then turn the TV on to see if DIM VDC jumps up at all.

[vinceroger69]

Re: Toshiba 19BL502B replaced diode worked, now not working

in the other thread dim is 2.3 v

[budm]

Re: Toshiba 19BL502B replaced diode worked, now not working

I will wait see what he gets on the DIM line when TV is first turned on, the 0.23V he is getting right now is too low.

[vinceroger69]

Re: Toshiba 19BL502B replaced diode worked, now not working

what is dim line purpose?

[budm]

Re: Toshiba 19BL502B replaced diode worked, now not working

To adjust the backlights level.
Typical dimming control:
Analog dimming: 1Vdc = min backlights, 5V = max backlights
PWM dimming: 10% pulse width = min, 90 % pulse width =max.

[vinceroger69]

Re: Toshiba 19BL502B replaced diode worked, now not working

thanks i was just reading up on pwm-dim theres so much to learn in regards to repairing electronics

[David-OLW]

Re: Toshiba 19BL502B replaced diode worked, now not working

I expect the Dimming control line to be higher than that.
BL-ON is OK @3.04V.
Put the black probe on the chassis, red probe on the DIM then turn the TV on to see if DIM VDC jumps up at all.

In standby it is zero on turning on it goes up to 3.09 volts then slowly reduces (over about 10 seconds) to 0.23, have repeated several times.

Thanks David