RCA RLC3708A No Backlight Adjustment.

[Doug]

Pressing "Input 2580" on the aftermarket remote opens the service menu.
I navigate to: "Other Setting" - "BackLight Adjustment"
The numerical scale goes from Zero to 100.
I have tried many different settings using the setup and service menus.
This (ccfl) LCD has good picture and all other settings are adjustable.
A factory reset defaults the backlight setting to 80.
The BackLight Adjustment setting does nothing.
The picture is almost too dark to watch.
This TV was built in March of 2012.
This model is also branded as Curtis, Proscan and maybe others.

[tom66]

Re: RCA RLC3708A No Backlight Adjustment.

You should check the BL ADJ or DIM or BRI pin on the inverter board, see if the voltage on it changes as you adust the backlight control on the user menu. Usually it ranges from around 0-0.3V (minimum) to about 2.5-3.3V (maximum)

[Doug]

Re: RCA RLC3708A No Backlight Adjustment.

I checked the DIM pin on the inverter board,the voltage on this pin did not change as i adjusted the BackLight control with the user menu. The voltage on the DIM pin did not fluctuate from .3V (minimum).
I applied .6V to the DIM pin on the inverter IC using an almost dead coin battery and the backlight brightened instantly.
Thanks so much to tom66.
He nailed this perfectly.

[budm]

Re: RCA RLC3708A No Backlight Adjustment.

Did you find out if it uses PWM DIMMING (FREQ around 200Hz, 10% pulse width = min, 90% pulse width = max brightness) or if it uses Analog dimming?

[Doug]

Re: RCA RLC3708A No Backlight Adjustment.

No, I did not find out if it uses PWM dimming or Analog dimming.
I have soldered a small wire to the DIM pin.
Applying about .9V -1V to the DIM pin brightens the image nicely.
This TV has been on for about 30 hours since this work-around.
Thanks again!

[budm]

Re: RCA RLC3708A No Backlight Adjustment.

If you remove the DIM control wire feeding the Inverter board, if it is PWM on that control wire, the backlights should then be at full brightness, if it is analog on that control wire, then the backlights will be off.