Toshiba 46rv350u No backlight, No picture but has sound

[dick_barton]

Re: Toshiba 46rv350u No backlight, No picture but has sound

If there is 0V across R8141 then either the opto is not being switched on or it is open circuit or you do not have the 5V supply to that circuit?

[fg42pr]

Re: Toshiba 46rv350u No backlight, No picture but has sound

If there is 0V across R8141 then either the opto is not being switched on or it is open circuit or you do not have the 5V supply to that circuit?

Any idea how I could check for voltage getting to that circuit. My diagram skills are pretty weak
Whatever the problem is it must be common because my original board and the used one I bought have the same results.

[dick_barton]

Re: Toshiba 46rv350u No backlight, No picture but has sound

With the set disconnected from the mains and your meter set to ohms measure between P812A (pins 4,5,6) and P812B (pins 4,5,6) which is the 5.1V supply line for continuity between both connectors.

[budm]

Re: Toshiba 46rv350u No backlight, No picture but has sound

What resistance do you get on R8141?
Are you sure you are getting 0.50VDC between pin 3 and pin 4 of the OPTO? That will indicate the PHOTO Transistor is turned on.

[dick_barton]

Re: Toshiba 46rv350u No backlight, No picture but has sound

Immediately after powering up the tv one of the fused resisters (rgdu5m-5e) located at r850 released a small plume of smoke and was very warm. Began testing output voltages and discovered 24v was not going to the inverter.

I think you have lost Line2 when R850 smoked. Line2 is used to switch on the opto Q813

Please can you check the resistance of R850 with the set disconnected from the mains.

[budm]

Re: Toshiba 46rv350u No backlight, No picture but has sound

I think you have lost Line2 when R850 smoked. Line2 is used to switch on the opto Q813

Please can you check the resistance of R850 with the set disconnected from the mains.

R850 (inrush current limiter) on BOTH boards?
Is he working on the new board or the original board?
At this point he needs to run the power supply board by itself first.
BTW, if the bypass relay SR81 has bad contacts or not activated to bypass the R850 or shorted load, then the resistor will get hot and burn up when TV is pulling full current, that is one of the common failure in this Toshiba power supply setup.
Just do the search on B.C. for 'SR81' and you will see.
https://www.badcaps.net/forum/search...archid=7036392

[dick_barton]

Re: Toshiba 46rv350u No backlight, No picture but has sound

I'm at a loss. After reading your reply and checking again, R850 gave a plume of smoke on the "original board" after changing the fuse.

The replacement board doesn't seem to have solved the problem, possibly worse now having no sound.

[fg42pr]

Re: Toshiba 46rv350u No backlight, No picture but has sound

What resistance do you get on R8141?
Are you sure you are getting 0.50VDC between pin 3 and pin 4 of the OPTO? That will indicate the PHOTO Transistor is turned on.

I had 5.07v between pin 3 and 4
r8141 was giving me reading in the millions

[fg42pr]

Re: Toshiba 46rv350u No backlight, No picture but has sound

R850 (inrush current limiter) on BOTH boards?
Is he working on the new board or the original board?
At this point he needs to run the power supply board by itself first.
BTW, if the bypass relay SR81 has bad contacts or not activated to bypass the R850 or shorted load, then the resistor will get hot and burn up when TV is pulling full current, that is one of the common failure in this Toshiba power supply setup.
Just do the search on B.C. for 'SR81' and you will see.
https://www.badcaps.net/forum/search...archid=7036392

I have been testing both boards and getting exact same results. R850 is showing open circuit on both boards.

[fg42pr]

Re: Toshiba 46rv350u No backlight, No picture but has sound

so I opened up sr81 on both boards and they had dirty contacts. you think just changing out r850 will do the trick??

[budm]

Re: Toshiba 46rv350u No backlight, No picture but has sound

I had 5.07v between pin 3 and 4
r8141 was giving me reading in the millions

OK, so it is not 0.5VDC as reported before, that is important.
It means the OPTO is not turned ON.
So what happen to that R850? You did not change it yet?

[fg42pr]

Re: Toshiba 46rv350u No backlight, No picture but has sound

I'm going to have to order one. recommend any site or just use ebay and amazon?
I also read about the q860 also being the rebel possibly. How can we test this part?

[budm]

Re: Toshiba 46rv350u No backlight, No picture but has sound

I do not know where the Q880 is or what its function is.
BTW, the diagram DB provided is missing the the 5V STBY section.
I sure like to get the full manual.

[fg42pr]

Re: Toshiba 46rv350u No backlight, No picture but has sound

I'll start by replacing r850 and go from there. I'll update when I get the part in and test it. thanks for all the help.

[dick_barton]

Re: Toshiba 46rv350u No backlight, No picture but has sound

I'll start by replacing r850 and go from there. I'll update when I get the part in and test it. thanks for all the help.

Best to order a few. I think they will be needed.

[fg42pr]

Re: Toshiba 46rv350u No backlight, No picture but has sound

I ordered 2 of them.

[fg42pr]

Re: Toshiba 46rv350u No backlight, No picture but has sound

1X 5J2R0 2 ohm 5 watt cement fusible resistor - will replace RGDU5M-5E (1.8 OHM)
http://www.ebay.com/itm/142032672375

[fg42pr]

Re: Toshiba 46rv350u No backlight, No picture but has sound

Ok so I finally had some time to replace R850 and once i powered it on it instantly blew F820
I was hoping those dirty contacts would have been the problem but I was not fortunate.

[budm]

Re: Toshiba 46rv350u No backlight, No picture but has sound

As indicated in my post 26, you may have shorted load on the output side of the resistor. More in-depth troubleshooting required.

[fg42pr]

Re: Toshiba 46rv350u No backlight, No picture but has sound

I'm willing to go further if someone has the knowledge to help me out with this. I'd much rather fix this than buy a replacement board.