Flourescent bench lamp

[Radio Fixer]

I thought of that and that's why I will leave the main overhead shop light as 'old' ballast. But for a bench magnifying lamp it doesn't matter, I always turned it off when listening anyway. With the magnetic ballast it was very noisy ... maybe due to flicker in the gas and fluctuating current with radiated interference from the wiring ?

Actually the electronic seems good, certainly better than before. Can hear it as it strikes the tube and then it seems OK. If I turn it off I don't hear any change, mind you I only have 10 foot of wire aerial at the mo !

Gary

[Nick]

What about putting the ballast in a diecast box (they only get warn, not hot, and you could bond the ballast to the base of the box), use a good in-line mains input filter (even though the ballast will already have one) and add some extra output filtering - ferrite ring maybe or shield the cables.

[Mark Hennessy]

The BAG unit I have is already encapsulated in an earthed metal case - the problem is that the output is several hundred volts at ~110kHz. It's a reasonably clean sine wave at the usual brightness I use (about 25%), but as you increase the brightness, the frequency falls and progressively becomes more distorted. At max, it's 50kHz and it looks a bit more like a triangle wave. The HF switching noise looks to be reasonably well attenuated on the 'scope (I don't have a spectrum analyser).

It's no wonder that radios are bothered by this, and I'm not sure how much help screening/filtering would be - not least because the whole tube is a radiating antenna... Still, the extra light is invaluable for close-up stuff and not really needed for lining up a set, so it works OK in practice - but it is a shame I can't replace all the lights down here with HF ballasts.

[Radio Fixer]

Maybe this bench lamp is good because the electronic ballast is in a completely enclosed die cast box with a metal plate bottom. As to the tube even that is shielded apart from the bottom by a die cast hood.

Anyway a success story for this lamp and leave the main over head strip one alone.

Gary