[sdiy] back-light troubles

[tuj]

Hi all:

I'm having problems with the back-light on an LCD display.  The light will 
turn on for about half a second when the unit is first turned on, and again 
for about half a second when the unit is turned off.  Its the typical 
yellow-green EL type back-light.  Finally, if I hold the switch in a 
certain spot very carefully when powering off, I can get the back-light to 
stay on, and I can hear a strange humming sound from either the power 
supply or the oscillator driver for the back-light.  I've verified 
continuity between the back-light and the oscillator pin outs, and wiggling 
the connections didn't change anything, so I think I can rule out the 
cable/connections.

Right now I suspect that possibly a capacitor in the oscillator section is 
bad?  I really don't know much about back-lights, could someone venture a 
diagnosis?

Thanks!  -tuj