BEKO LCD 32WLA520HD (LM) - help with Dimming on Service Menu

[yaye]

Hi, does anyone understand how to dim the backlight of this television? The service menu has a 'Dimming' option which only seems stable on 255 (full on) or 0 (dim). Anything between 31 and 242 causes the screen to flash as if the backlight isn't fully igniting (more likely to happen when cold also). I dont want to set it to a value that causes it to stay off, as the menu is only responsive when the backlight is lit. Basically I need to know if it's safe to keep the value at zero. A service manual (or at least the entry for dimming) would be helpful. Also information on the 'ISP' and 'PIP' entries would be useful. Please help!