Rod Speed wrote:

Fredxxx wrote
Rod Speed wrote
wrote
R D S wrote
Phil L wrote

Is there a starter? - 35p each, I'd try this first

Thought the same, done that.

So you've got switchstart fittings. Then it's wrong starters,
bad tubes or bad contacts. The capacitor can't cause this.

Corse it can.

And is in fact by far the most likely problem when the tubes
arent connected in series after the things he has tried already.

The capacitor will be across mains in.

Yes.

Can you explain, assuming the supply impedance is in the
order of a fraction of an ohm, why a capacitor can cause the
perturbations in voltage supply to cause a substantial flicker?

You havent established that it is causing perturbations
in the voltage supply. And it can obviously do that by
not being a viable cap anymore anyway.

In this permissive society the capacitor can be anything it likes. But
the only way it is going to significantly affect the operation of the
tubes is by 'being' a sufficiently low impedance to operate the
over-current protection device protecting the supply. The OP would have
noticed such acting-out by the capacitor.

--

Roger Hayter