although mercury vapor & metal halide ballasts seem to be prone to buzzing as they age,i would think any ballast would become noisy,if maybe the laminations,cane undone.

I've seen both MV and MH ballasts get equally noisy. The most common source of noise seems to result from the coil becoming loose around the core. I have successfully repaired this by applying class H transformer varnish on and around the coils...usually works like a charm. Problem is that the varnish that I have is hard to find....luckily I had some at work.

although its more expensive,why not use expoxy resin,if you pot the ballast with epoxy the ballast would be very quiet,also epoxy would last longer than varnish because it has a very high tollerance of tempatures,the epoxy also reduces hot spots on the windings,prolonging the life.

although mercury vapor & metal halide ballasts seem to be prone to buzzing as they age,i would think any ballast would become noisy,if maybe the laminations,cane undone.

Yes, any ballast can become noisy,even fluorescent and HPS.I have a couple fixtures with HPS ballasts, that are buzzing a little more than most.

I used Epoxy on my Silverliner's Ballast and it sure made it quiet!

there is one flourescent fixture in my school that needs replacing the ballast hum is very prominent,the lamp has very blackened ends,and the old lamp is destroying the ballast!

i also recall a ballast in a flourescent fixture overheating,when it burned out it had the most awful smell!