On Sat, 21 Apr 2018 07:49:08 -0000 (UTC),
(Andrew Gabriel) wrote:

snip

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

It's not really a potential divider because the tube is far from a
resistor.

Ok ... but can you not have a potential divider (in crude function) on
AC and using a choke and a tube? (Genuine question).

To a first approximation, it's a constant voltage device,
and to a second approximation, the voltage across it varies inversely
with the current flow. So a reduction in mains voltage will drop the
voltage across the inductor, which will drop the current in the circuit,
and the second order approximation will raise the tube voltage because
of the lower current. This could trigger a marginal starter.

Cool, so I was asking the right sort of question at least. ;-)

snip

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?

Tubes changed their ratings, whereas starters didn't. The 4-80W
starters were originally for tubes up to 5'. 5' tubes dropped from
80W to 65W to 58W over time.

Interesting, thanks.

6' tubes dropped from 85W to 70W, with
the 70W tube having a higher tube voltage than the original 85W tube
(so it runs at 70W on original 85W ballasts).

Ahhhh ...

FWIW, the sticker on the actual fitting says '1 x 70W' but the choke
could be the 85W as you say (I'll check when I get a mo).

So a starter for an old 80W tube might not work on a current 70W tube.
It would have been more accurate to rate them by tube length where the
original 4-80W starter would have been tubes up to 5', although even
that's not perfect. There was generally enough leaway they worked
outside their ratings, but you hit one that doesn't.

Well I seem to have hit at least 2 (of the 6 I bought) that cause the
lamps to flick off (possibly when they get warm or after running for a
couple of hours or some other external influence, like incoming supply
lower voltage etc) but does it explain why another three don't
actually start a tube at all (till it's already been warmed up via
another starter)?

I notice that starters nowadays seem to be 4-65W (which is probably
exactly the same as the old 4-80W starter), 70W is a separate starter,
also a 70-100W starter (which is probably exactly same as old 125W
starter for old 8' tubes).

LOL ... crazy eh, as you say.

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

I would look for a 70W starter or 70-100W starter.

Because of the 'discussion' I'm having with this eBay seller I think
(just for the S&G's etc) I'd like to try a 'branded' 4-80W starter,
just to see if they can do the job.

OOI, the starters I have that are playing up are branded 'Star' (with
red writing)

Cheers, T i m