Toshiba 40E200U1 turn ON but no backlight, no video

[alfredomfr1]

Re: Toshiba 40E200U1 turn ON but no backlight, no video

The picture

[budm]

Re: Toshiba 40E200U1 turn ON but no backlight, no video

https://www.badcaps.net/forum/attach...9&d=1472859377

OK, check the DCV on the Collector (C) of that Transistor Q801 with ref to the primary circuit GND.
I exepct it to be around 18~20VDC range, I see it now that is the switched Transistor for supplying Vs for the IC.
The AC Voltage is generated by the AUX winding of the STBY power transformer, it is rectified by D803 and fed through R805 and is filtered by C802 and then fed to the Collector of Q801. This AUX Voltage is also the running Voltage for the STBY SMPS IC.
Q801 is turned on by OPTO PC902 (you can see it is bias ON through R810 when OPTO is turned on),

[budm]

Re: Toshiba 40E200U1 turn ON but no backlight, no video

Switched Vs circuit.
BTW, did you try having everything all hooked up but not the LVDS cables connected to see if the 12V/24V will return?

[alfredomfr1]

Re: Toshiba 40E200U1 turn ON but no backlight, no video

Q801 collector: 28v, with lvds cable disconnected 12v/24v not present

[budm]

Re: Toshiba 40E200U1 turn ON but no backlight, no video

So the switched Transistor is getting the input Voltage but no output on the EMITTER leg.

[alfredomfr1]

Re: Toshiba 40E200U1 turn ON but no backlight, no video

Yes, 0v on emitter leg

[dick_barton]

Re: Toshiba 40E200U1 turn ON but no backlight, no video

It seems as though ACD comes from the main board and is not required to power up the power supply secondary voltages according to the following link. It says to jumper 5V stby to PS_On and also 5V stby to BL_ON. The 12V and 24V should come up as well as the backlights. I assume this is with the main board disconnected from the power supply.

https://www.badcaps.net/forum/showth...light=40E200U1

[alfredomfr1]

Re: Toshiba 40E200U1 turn ON but no backlight, no video

I already did, 12v /24v not present

[budm]

Re: Toshiba 40E200U1 turn ON but no backlight, no video

Need to measure DCV between the two legs on the cold side of OPTO PC902, and between the two legs on the HOT side OPTO PC902. when PS-ON is present.

[alfredomfr1]

Re: Toshiba 40E200U1 turn ON but no backlight, no video

I will do that tomorrow in the morning
Thanks for reply