The capacitor is on pin 19 of the chip. Its the soft start for the lamps.
For normal function, I think the cap has to fully charge (goes to around 9v
i think), but the OLP circuit doesnt cut in till 2.5v. I dont really want to
tinker permanently with that cap.

Anyone know where I can get a BIT3105 (in the UK), I might change it out in
case its faulty.

Michael.

"James Sweet" wrote in message
news:Y403f.31290$A52.27045@trnddc02...

"Michael" wrote in message
ng.com...
I have a dell 1504FP (LCD monitor). The backlight doesnt work for a
period
of time.

On close examination with a scope on the PSU board, BIT3105 (lamp
controller
IC) is getting confused. It has several pins to do with OLP (open lamp
indicator)- basically the chip switches itself off if it thinks one of
the
lamps is open circuit. The lamps are definitely all working. I can
recreate
the problem by disconnecting any one lamp.

The OLP circuit waits for a cap to reach 2.5v before monitoring- if I
drain
that cap, the monitor works.

Could someone look at the BIT3105 data sheet and tell me how to disable
the
OLP circuitry- I dont care if it shortens my monitor life. Please help.

Thanks in advance.

Michael.



Perhaps a resistor across that capacitor would make it less sensitive? How
are you draining it? Just shorting across it?