On Fri, 20 Apr 2018 21:55:35 +0100, ARW
wrote:

snip

The
starter is a one shot process.

Agreed, it *should* be but I was wondering under what criteria it
might try to kick in again after say a couple of hours? eg, what if a
ballast was going or a tube etc (except the ballasts have been there
since I fitted the units possibly 30 years ago (could be less [1]) and
they currently have new Philips tubes).

Once the tube is lit it has no further use.

Agreed.

snip

Voltage drop to the house?

Well, that's the sort of thing I am open to but if I understand it
right, the ballast and tube are in series across the mains (forming a
potential divider) and the starter is in parallel with the tube on the
other side of the filaments. The starter is a voltage / current
sensitive device so it *could* be falsely triggered if 1) the voltage
goes above it's trigger voltage [1] and / or 2) the starter is made
such that it's over sensitive (to voltage)?

I know the bottom line is that the electronic (and old Philips
70-125W) starters work, just that the new 4-80W ones don't (or not
fully).

Would you use / have you successfully used 4-80W starters on 70W tubes
do you know / remember please Adam?

I think I'll try to pick up some branded (Philips?) 4-80W starters and
see if they work reliably in my lamps.

Cheers, T i m

[1] Where the gas (Argon / Neon) in the starter switch capsule get's
hot enough to heat the bi-metallic switch and close the contacts.