Toshiba 46G300U1 Dead

[Ltank]

LCD tv power supply turns on as soon as its plugged in to ac power. Has 5vdc
standby, 24vdc to inverters and 12 vdc to main board. The Power command to the PS is constant 3.45vdc, button does not turn it on or off. The Inverter command is .47. I can make the inverter turn on and then substitute a dim command and I can vary the backlight brightness.
Basicly the main board is shot. no control of P.S. on/off, not turning back light on, does not give a dim command. No Menu can be seen when jumpering on the backlight and dim control. Backlight works fine.
The main board is a 461C2H51L12 Rev.1C. I could not find a new or used replacement. I found a troubleshooting guide (not much help) but no service manual or schematic. I checked the SMD transistors associated with pins
13 power on and pin 16 inverter. They checked good. Ayny Ideas? Pointers?

[sugar_ray]

Re: Toshiba 46G300U1 Dead

Hey dude!! Just ended up going through the same thing with a toshiba. Similar symptoms. However when measuring the output on the power supply I could see nothing was being sent to the main board. I had power going to the PS via the ac cord but that's as far as it was going. Tv wouldn't turn on using remote or button. Just dead!! Have you ruled out your power supply??
I know you said you have backlight but there may be a portion of the PS that isn't supplying.
Made a short video of the simple repair.

https://www.youtube.com/watch?v=Bk9a...ature=youtu.be

Also shopjimmy & retechtv supplies your ps board if that ends up being the issue. Ive dealt with both of them and will say both are great to deal with. Hope this helps? If it is 100% for sure your main, you may be in the ( is this worth fixing? ) range. Mains seem pricey for this model

http://lcdtvparts.ecrater.com/p/1220...1-e89d87e81b3d

http://www.retechtv.com/search?q=Toshiba+46G300U1

http://m.shopjimmy.com/catalogsearch...shiba+46G300U1

[Ltank]

Re: Toshiba 46G300U1 Dead

Power supply can be turned on, backlights can be turned on and dimming controls all work is jumpered simulating the commnans from the main board. #13 is Power on and
16 is the backlight on command and I think 14 or 15 is the Dim command 4.5vdc makes the screen bright. I know the PS and inverters are fine. I can turn on the tv simulate a dim cmd 4.5vdc to make back light bright. The main board does not give any sighns of life on screen. No OSD no audio when supplying audio through HDMI switching throught the inputs. Disconnecting the T-Con did not change anything.

[sugar_ray]

Re: Toshiba 46G300U1 Dead

Alright!! Sounds like you've done we'll in narrowing down the issue which is in the main. Just got to ask yourself if its worth replacing the main? Looks like an expensive board to replace. Let us know how you make out

[Ltank]

Re: Toshiba 46G300U1 Dead

Most main boards are expensive to buy new and even used. The voltage regulators are good as are the caps, and SMD transistors. hard for sure with no schematic

[sugar_ray]

Re: Toshiba 46G300U1 Dead

Ya man I hear ya!! I use to spend endless hours diagnosing components on bad boards. So unless its a dead obvious exploded cap ill just make a Board swap if I'm confident I've diagnosed a bad board correctly