sony kdl46s4100

[nomoresonys]

Re: sony kdl46s4100

OK, this power supply board has pullup resistor built-in on the BL_ON control pin, which is connected to the main board, the main board will pull this line LOW to keep the backlights off, so when you remove CN303, the backlights will come on, this is how you find out if the inverter is working or not by pulling the CN303 as long as the power supply suppling the B+ to the inverter circuits is OK. So if the backlight stay on without going offf when you remove CN303, it means that your inverter/balancer/lamps are OK, the problem is then in the main board. You can see the BL_ON signal is fed to Q703 ON PAGE 47 of the service manual.
That is why on my post 28 I indicated that we need to check the BL_ON pin.

ok, I checked cn303, cn302 and cn301, with cables plugged in, all voltages were correct, should I measure another way, do you think the connector wires on cn303 could be bad, thanks for all the help, I think we're getting close.

[nomoresonys]

Re: sony kdl46s4100

OK, this power supply board has pullup resistor built-in on the BL_ON control pin, which is connected to the main board, the main board will pull this line LOW to keep the backlights off, so when you remove CN303, the backlights will come on, this is how you find out if the inverter is working or not by pulling the CN303 as long as the power supply suppling the B+ to the inverter circuits is OK. So if the backlight stay on without going offf when you remove CN303, it means that your inverter/balancer/lamps are OK, the problem is then in the main board. You can see the BL_ON signal is fed to Q703 ON PAGE 47 of the service manual.
That is why on my post 28 I indicated that we need to check the BL_ON pin.

is the bl_on pin the one in cn303?, thanks.

[drpj23]

Re: sony kdl46s4100

It should say BACK_LIGHT_ON/OFF.
It should be the connector in the top right of the power supply.

[budm]

Re: sony kdl46s4100

CN303 PIN 2, it should have bl_on printed next to that pin, it should be >3V for the backlights to be on.
Please look at the PDF of the power supply I attached, see page 4, post 30.

[nomoresonys]

Re: sony kdl46s4100

CN303 PIN 2, it should have bl_on printed next to that pin, it should be >3V for the backlights to be on.
Please look at the PDF of the power supply I attached, see page 4, post 30.

bl_on measures .17 on the 20 dcv setting, that's the rebuilt board shop jimmy sent me, thanks.

[budm]

Re: sony kdl46s4100

That is measured when you turn on the power switch? You may have some other fault that causes the main board to stay in shutdown. This chassis may have T-CON fault detection circuits.

[nomoresonys]

Re: sony kdl46s4100

I'm pretty sure my original board measured 3 or 3.5, thanks

[nomoresonys]

Re: sony kdl46s4100

yes power is on when I measured.

[budm]

Re: sony kdl46s4100

Put the old board back in then to see.

[nomoresonys]

Re: sony kdl46s4100

I got two 1 857 092 11 boards from shop jimmy, and this 1 857 092 41, I'm beginning to think every board they sent me was a dud.

[nomoresonys]

Re: sony kdl46s4100

Put the old board back in then to see.

switced boards getting .18 at bl_on and 3.3 at bl_dim.

[nomoresonys]

Re: sony kdl46s4100

so that means I'm not getting enough bl_on voltage from the main board?, thanks.

[nomoresonys]

Re: sony kdl46s4100

OK, this power supply board has pullup resistor built-in on the BL_ON control pin, which is connected to the main board, the main board will pull this line LOW to keep the backlights off, so when you remove CN303, the backlights will come on, this is how you find out if the inverter is working or not by pulling the CN303 as long as the power supply suppling the B+ to the inverter circuits is OK. So if the backlight stay on without going offf when you remove CN303, it means that your inverter/balancer/lamps are OK, the problem is then in the main board. You can see the BL_ON signal is fed to Q703 ON PAGE 47 of the service manual.
That is why on my post 28 I indicated that we need to check the BL_ON pin.

looked at page 47, having a hard time finding Q703, found Q603, 306, 910, 601 , 602, 901.

[budm]

Re: sony kdl46s4100

You can leave everything connected and just cut the BL_0N wire, make sure to leave it long enough to be able to splice it back together, then when you turn on the TV, you should see the backlights on. Right now the BL_ON LINE is not going high to turn on the backlights. We already know that the backlights are OK since you can turn it on by removing CN303.
You should also see what voltage you have at PS_ON pin.

[nomoresonys]

Re: sony kdl46s4100

You can leave everything connected and just cut the BL_0N wire, make sure to leave it long enough to be able to splice it back together, then when you turn on the TV, you should see the backlights on. Right now the BL_ON LINE is not going high to turn on the backlights. We already know that the backlights are OK since you can turn it on by removing CN303.
You should also see what voltage you have at PS_ON pin.

power off ps_on 3.2, power on .02.

[budm]

Re: sony kdl46s4100

That is correct, this SONY use active low to turn on the power supply, most TV use >3v to turn on, 0~2V to turn off, so the main board is sending out correct PS_ON signal of 0V, the one that is wrong is the BL_ON which is active Hi which it is not working. You will have to cut that BL_ON wire for now to get the backlights to come on to find out if you can see the pictures on the screen.

[nomoresonys]

Re: sony kdl46s4100

That is correct, this SONY use active low to turn on the power supply, most TV use >3v to turn on, 0~2V to turn off, so the main board is sending out correct PS_ON signal of 0V, the one that is wrong is the BL_ON which is active Hi which it is not working. You will have to cut that BL_ON wire for now to get the backlights to come on to find out if you can see the pictures on the screen.

cut bl_on, now have same pattern as when cn302 is unplugged.

[nomoresonys]

Re: sony kdl46s4100

I mean cn303.

[budm]

Re: sony kdl46s4100

That is, we want to have backlights on, then you should see pictures on the screen if the main board and the T-CON boards are OK. The backlights are just the light sources and nothing else. So do you see any pictures on the screen?

[nomoresonys]

Re: sony kdl46s4100

That is, we want to have backlights on, then you should see pictures on the screen if the main board and the T-CON boards are OK. The backlights are just the light sources and nothing else. So do you see any pictures on the screen?

no just the same test patterns as when cn303 was unplugged.