RE: Light electronics question

Shiao Wang wrote about problems he is having with his flourescent lighting:

>1. Turn on the switch, lamps glow faint orange at the ends but do not come
>on. They come on after a few minutes (times vary and unpredictable) by

>2. Turn on the switch, nothing happens. Twist the bulb slightly and it comes
>on and lights fine.

>3. Turn on the switch, nothing happens. Touch or tap the metal hood and the
>lamp comes on and lights fine. This only happens with a T-8 Triton bulb.
>Regular T-12 bulb works fine.

My first question is: are using a T8 ballast?
Typically T8 tubes will not run very well with T12 ballasts since the tube 
charateristics are different.
Points 2 and 3 seem to indicate that the tube lights when it's mechanically 
disturbed.  My guess is that as the tube moves in the socket it momentarily
opens the connection (tube to socket) which places the ballast in a no-load
state.  Under no-load the ballast's output voltage increases.  When the tube 
re-makes the connection (to the socket), the high voltage 'spike' causes the
gas to ionize and the tube lights...(note: flourescent tubes only require a
high voltage to start - once the gas ionizes the internal impedance drops and
the lamp remains 'on' at a much lower voltage.)

Two factors which affect tube startability are age and temperature - new tubes
start easily, older ones require higher starting voltages, and the warmer the
tube the easier it is to start.  

BTW - Excellent T8 ballasts are made by Conik Technologies and Osram/Sylvania.
	- Conik makes 4' twin tube dimmable ballast (<$60cdn)
	- The Osram/Sylvania ballasts come in several versions and they
	  feature independant output drivers (ie. if one tube fails the others
	  remain ON.)

Hope this helps...

Torsten Tiedtke
Lynden, Ontario

"Electronics used to be a hobby - now it's a job..."