RCA 32LB30RQD - Power on, No picture, sound, or backlight

[caphair]

All the voltages are present from standby 5v to 24v to inverter. After some more testing, I noticed the BL_ON command only goes to 0.06v. The BL_ON command comes from the mainboard labeled "inverter dc" as shown in one of the pics which when measured from top down gave 0v 5v 0v (this last 0v connector is the BL_ON on inverter side) . Is it safe to try jumping this with the 5v next to it to see if the picture comes on?

Also to note, pressing the power button after it has been turned on does not turn it off, need to unplug the set at that point.

The person I'm troubleshooting this for says the fault occured after a power surge.

[caphair]

Re: RCA 32LB30RQD - Power on, No picture, sound, or backlight

Fuses on the t-con and inverter both tested ok. Would there be any on the mainboard?

[budm]

Re: RCA 32LB30RQD - Power on, No picture, sound, or backlight

"Also to note, pressing the power button after it has been turned on does not turn it off" That indicate main board problem when you do not have control to turn the TV off.
There are some 3-pin Voltage regulators IC that you may want to check the Voltages on.
https://www.badcaps.net/forum/showthread.php?t=22231

[caphair]

Re: RCA 32LB30RQD - Power on, No picture, sound, or backlight

Ok here are the measurements to the regulators on the main board.

They will be posted in this order pins 1, 2, 3 (left to right with tab on top)

U1 - 1117AG
0v
1.24v
2.97v

U2 - 1117B 33
0v
3.3v
4.94v

U4 - 1117AG
0v
1.24v
3.30v

U6 - 1117AG
0.58v
1.83v
3.30v

There's 1.24v present on the three adjustable regulators across pins 1 and 2

[budm]

Re: RCA 32LB30RQD - Power on, No picture, sound, or backlight

They are OK
I myself never have luck fixing the SAMSUNG main board.
You can remove the wire from the BL_ON connector to the main board and then use the resistor to force on the backlights to see if you can get normal pictures and normal function of the TV.

[tom66]

Re: RCA 32LB30RQD - Power on, No picture, sound, or backlight

The input to U1 looks odd, 3V is an unusual rail voltage. Try testing that one again? Its output is good but maybe if that's supposed to be a 3.3V rail it could cause issues. Switching converter etc. for CPU logic/IO.

[caphair]

Re: RCA 32LB30RQD - Power on, No picture, sound, or backlight

They are OK
I myself never have luck fixing the SAMSUNG main board.
You can remove the wire from the BL_ON connector to the main board and then use the resistor to force on the backlights to see if you can get normal pictures and normal function of the TV.

What value resistor, does it matter? Could I just short the 5v to bl_on using multimeter in current test mode?

[caphair]

Re: RCA 32LB30RQD - Power on, No picture, sound, or backlight

The input to U1 looks odd, 3V is an unusual rail voltage. Try testing that one again? Its output is good but maybe if that's supposed to be a 3.3V rail it could cause issues. Switching converter etc. for CPU logic/IO.

Tested again, same values.

[tom66]

Re: RCA 32LB30RQD - Power on, No picture, sound, or backlight

I see at least one switcher, U5. Near the power connector from the power supply. What is the part number of U5?

[budm]

Re: RCA 32LB30RQD - Power on, No picture, sound, or backlight

What value resistor, does it matter? Could I just short the 5v to bl_on using multimeter in current test mode?

You have to disconnect the cable because if the switched transistor on the main board is on when you apply 5V it will draw lots current into fully on transistor and it not allow the BL_ON line to go high.

[caphair]

Re: RCA 32LB30RQD - Power on, No picture, sound, or backlight

You have to disconnect the cable because if the switched transistor on the main board is on when you apply 5V it will draw lots current into fully on transistor and it not allow the BL_ON line to go high.

Ok so unplug and short 5v pin to bl_on pin of the connector? Do I need a resistor or can use a wire?

[caphair]

Re: RCA 32LB30RQD - Power on, No picture, sound, or backlight

I see at least one switcher, U5. Near the power connector from the power supply. What is the part number of U5?

I'll take a look when I'm home later. Just left

[budm]

Re: RCA 32LB30RQD - Power on, No picture, sound, or backlight

I use 100~500 Ohms resistor.

[caphair]

Re: RCA 32LB30RQD - Power on, No picture, sound, or backlight

i see at least one switcher, u5. Near the power connector from the power supply. What is the part number of u5?

fr9886

[caphair]

Re: RCA 32LB30RQD - Power on, No picture, sound, or backlight

I use 100~500 Ohms resistor.

Used a 100ohm resistor and set fired up with a picture and now responds to power off.

Can I run it like this? Any idea from this what could be the bad component/s?

[budm]

Re: RCA 32LB30RQD - Power on, No picture, sound, or backlight

You need to trace that BL_ON connection of the main board to see where it goes to, it should be connected to a switched Transistor/MOSFET which is turned on by the processor, not going to be easy.
The BL_ON must be applied after PS_ON is applied to allow the power supply to become stable before the inverter kicks since it draw the most power from the power supply.

[caphair]

Re: RCA 32LB30RQD - Power on, No picture, sound, or backlight

You need to trace that BL_ON connection of the main board to see where it goes to, it should be connected to a switched Transistor/MOSFET which is turned on by the processor, not going to be easy.
The BL_ON must be applied after PS_ON is applied to allow the power supply to become stable before the inverter kicks since it draw the most power from the power supply.

Yeah doesn't look easy I already tried a bit before the resistor thing. Weird though it worked the first try, went to connect to a source and now isn't working. Just turns on with backlight but doesn't give a picture with "no signal" as initial try

[budm]

Re: RCA 32LB30RQD - Power on, No picture, sound, or backlight

I think your main board is dying.

[caphair]

Re: RCA 32LB30RQD - Power on, No picture, sound, or backlight

I think your main board is dying.

As in not repairable?

I traced that bl_on pin to this cluster. Those two transistor looking components didn't measure any shorts in any pin configuration

[budm]

Re: RCA 32LB30RQD - Power on, No picture, sound, or backlight

You need to check the E-B DC Voltage to see if it is biased on/off when the TV is turned on and off.