Xenarc CCFL brightness reduced after modification - please help me debug
recently I extended the high voltage wires from the inverter to the CCFL on my Xenarc 700TSV. I'm still alive after the experience and so is my Xenarc. I used hi-flex PVC insulated test lead cable. The extended cable run is about 8 inches long. There's no crackling, or arcing that I can see going on but my fear is that somehow the voltage is being lost along the run.
My problem is the CCFL brightness now seems to be low. I like to be as precise as possible about things but I have no way of measuring how low it actually is. My Xenarc has been in bits for best part of 3 months so I can't remember how bright it should be. I know these screens are not exceptional in this respect (hence the upgrade project), but this just seems too dim.
Using the OSD menu I have checked that the backlight setting is on 99. Indeed reducing it reduces the backlight intensity even further so the control mechanism seems to be working.
I've read about people saying that the Xenarc benefits from being supplied from cleaner power supply than may be available from a car, so I'm supplying it from the output of a 12V linear regulator. It says in the manual that the screen's minimum DC input voltage is 11V. I've just measured the input on my screen and it falls to 10.2V when everything's on. I think this is to do with the regulator's internal loss as my bench power supply is 12V. Technically this is out of spec so maybe that's my problem. This is something I'm going to investigate and I'll probably try bypassing the regulator on the bench to see if that extra 1.8V makes any difference to the brightness. Anyone have any anecdotal evidence that backlight brightness on a Xenarc is a function of input voltage in the range 10-13V?
I suppose I really need to be able to measure the output voltage from the inverter, but I suspect that's not easy with basic test equipment. Maybe there's some kind of resistor network I could apply to it to scale the voltage range down so that it's measurable with a standard digital meter? That then begs the question:- what voltage am I expecting to see out of the inverter?
If that method works then I guess I could then tap off the voltage at the CCFL end of the extension and see if there's been a voltage drop alon the wires. BTW are CCFLs supplied with AC or DC? and if it's AC, what sort of wave is it?
The other thing I wondered was whether there is any way I can probe the (low voltage) 4-pin input connector to the inverter board to test for expected voltages. I don't know the pinout of this - maybe someone could assist. I assume it's got to be a supply rail, a ground, a brightness analogue/PWM input and something else? I just wondered if it was this side of the inverter where the problem lies.
Any help greatly appreciated.