Toshiba 40RV525u, backlight not working

[Hobby 1]

Hi All,
I picked up this TV recently off kijiji. The owner said it stopped working one day. The power LED and the Toshiba emblem light up and nothing else. I did a search on this forum for common problems and hoped that it was an easy fix. Probably a voltage missing from the power supply or a shorted component loading down the power supply. No such luck. All the voltages are there. No short found. No blown fuses found. The set was opened by someone but it does not appear that anything was touched inside. The boards match the ones in the earlier posts about this model. The inverter board shows no burn marks on either side. 24V is getting to the board and the 2 7.5A fuses are good. I can't find a datasheet on the inverter control chip, 'SEM2007'. Most pins are zero volts, 1 pin shows 15 or so volts so I am thinking the problem is with that chip or power to it. I also can't seem to find any image on the screen with a light close up to it. I can't tell what input it is on either. Can anyone offer suggestions for fixing or testing it further? Anyone have any info on this chip? I did a google search and did not find anything.

[budm]

Re: Toshiba 40RV525u, backlight not working

We need good clear pictures of the whole backside of YOUR TV showing all the boards, and then the good straight shot pictures of the power supply board.
You will need to test the DC Voltages of the power supply connector that goes to the main board, you MUST put down the pin name of each pin and follow by the Voltage reading when TV is OFF and when power switch is activated.

[Hobby 1]

Re: Toshiba 40RV525u, backlight not working

Connector P802/CN3
OFF ON
Pin 1 GND 0 0
2 GND 0 0
3 +24 0 +24.3
4 +24 0 +24.3
5 GND 0 0
6 GND 0 0
7 GND 0 0
8 +12 0 +11.9
9 +12 0 +11.9
10 NC 0 0
11 +5 +5 +5
12 +5 +5 +5
13 PWR 0 +4.4
14 ACD 0 .1
15 DIM 0 .1
16 INV 0 0

[budm]

Re: Toshiba 40RV525u, backlight not working

14 ACD 0 .1
15 DIM 0 .1
16 INV 0 0
If your data are correct then that means the main board is not sending the command signal to turn on the backlights circuit, no dimming command either.

[R_J]

Re: Toshiba 40RV525u, backlight not working

here is the SEM2007 data sheet, I doubt it's the problem, inverter may not be getting the on and dim signals

[Hobby 1]

Re: Toshiba 40RV525u, backlight not working

Any suggestions as to what to try next if it is the main board? Can the board be fixed? problem narrowed down to some component? Or just replace the main board?

[mmartell]

Re: Toshiba 40RV525u, backlight not working

It's a Toshiba - try heating the main processor with a hair dryer. You can try to trace the Inverter On pin but since there's a lack of schematics for main boards you mostly swap them out for a working one.