Backlight on trip computer problems????

[Chad Frederick <fredie@u.washington.edu>]

Q-List,

I got some questions about how the the way the computer is backlit on my 
86 4kcs Q.  When I first purchased my 4kQ about 5 months ago the trip
computer backlight when I turned the lights on would not always come on
with the instrament panel lights.  So I would give it a "little tap" and it
would then turn on.  Well most recently the "little tap" method has not
been working.  So, I for the 102nd time had to pull my instrament panel out
to find out what was wrong.  It is amazing that I never noticed this
before, but it appears there are 2 bulbs to backlight the trip computer.
Why are there 2 of these bulbs?  It looks like one of the two bulbs may be
burned out.  The bulb that looks burned out is the clear one, not the one
that has the "silvery matallic" color on the inside of the bulb.  

Now, when I pulled out both of the bulbs and turned on the computer and
hooked everything back up trying to troulbleshoot I found the computer LCD
display still worked, but of course no backlight.  Which light bulb then
lights up the LCD display then?  So I guess my question is, where can I
buy, (besides the dealer which is a couple of blocks from my apt) a
replacement bulbs for both of these.  Since that is probably my best bet.
If anyone has had this problem please let me know.  I feel like this may be
a tough one since many people probably have not explerienced this problem.
Man, I hope I do not have a short, damn electrical gremlines.

Chad Frederick
86 4kcs Q (My pride and joy)
84 318i (thank god I am selling it tommarrow)

P.S. I have always kind of wondered, what is the adjustment nob on the face
of the tachometer that you can access with an allen head, on the out side
ot the display glass for? (nice run on sentance)