[sci.electronics] Ballast Boxes

smlg1015@uxa.cso.uiuc.edu (10/30/89)

 When I moved into my present apartment, the fluorescent lights emitted
a loud buzzing noise.  Upon examination, the noise seemed to be coming
from something marked "Ballast Box: Class P".  I replaced it and the
noise stopped.  Can somebody tell me what a Ballast Box is and how it
works?  I opened the old one and found some kind of black paste surrounding
the wires.

Stuart Lichtenthal    smlg1015@uxa.cso.uiuc.edu

marty@puppsr3.princeton.edu (marty ryba) (10/31/89)

smlg1015@uxa.cso.uiuc.edu writes:
> When I moved into my present apartment, the fluorescent lights emitted
>a loud buzzing noise.  Upon examination, the noise seemed to be coming
>from something marked "Ballast Box: Class P".  I replaced it and the
>noise stopped.  Can somebody tell me what a Ballast Box is and how it
>works?  I opened the old one and found some kind of black paste surrounding
>the wires.

A ballast is a large transformer with some capacitors thrown in for starting
assistance.  It steps line voltage up to the approx. 300v needed to run a
fluorescent lamp.  It has several taps for heating the filaments inside the
lamps.  The capacitors act as shorts during starting to start one lamp first.
Once one lamp starts, the voltage drop across it drops, and the second lamp
starts immediately due to the greatly increased voltage across it.

The buzzing noise was some part of the transformer core that had cracked due
to age, stress, etc.  It was a good idea to replace it.  The black paste is
epoxy to seal the whole thing up (300v can kill, and these things are every-
where, so you have to be *very* careful).

I interned at GE designing fluorescent lamps.

Marty Ryba (slave physics grad student)
They don't care if I exist, let alone what my opinions are!
marty@puppsr.princeton.edu
Asbestos gloves always on when reading mail