Fluro lights
Trying to fix a twin 8W fluro light.
Just wondering, what sort of resistance range should the ballast be if it's good ? Old black Bal-co B4C 2/8L ballast.
Last edited by loopyloo; 28-10-17 at 11:20 PM.
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Been ages, but I don’t think there is specific resistance for a working / faulty ballast... I always figured if a new globe and starter (which I’ve always changed together) doesn’t fix it - change the ballast... Depending on which side of fail the ballast decides to go, you should either have a slow starting and dimmer globe, or a brighter and quicker burnt out globe you’ll get
loopyloo (28-10-17)
If it's a simple inductive type ballast, it's the inductance XL that's important and not so much the resistance of the winding.
So it's looking good if it's not an open circuit although you couldn't rule out an internal shorted turn but I've never encountered that.
Not much to go wrong with a mains powered fluoro lamp but heaps of possibilities in a battery powered (inverter) type.
Last edited by Skepticist; 28-10-17 at 11:08 PM. Reason: typo
loopyloo (28-10-17)
Hmmm twin 8W sounds like a smaller Aquarium lighting, DC probably in the 100 Ω range. Corrosion issues could be everywhere.Originally Posted by loopyloo
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loopyloo (29-10-17)
Not aquarium lighting and it's 240vac.
The ballast is around 300ohms.
Last edited by loopyloo; 29-10-17 at 09:21 PM.
That sounds good for the power you quoted at 8W and the inductive reactance will be much greater than that (like about 5-10x) at the mains 50Hz frequency.
The resistance only determines how much heat is lost in the ballast and, for 8W running load, it should be less than 1W
Got an inductance tester that can measure a large inductor? like up to 10H or so
Do the tubes light up very dimly with the starter removed?
loopyloo (30-10-17)
Nah no inductance tester.
Don't think the 2 tubes would light at all without the starters cos they're in series.
So if the ballast sounds good then it must be a bad connection somewhere. Typical for fluros eh ? ... a little while ago I found one of the tombstones has a crack in it and I think it's opening up when the tube is rotated into position. I'll find out when the glue dries.
Do the tubes look black at the ends?
Usually there'll be a tiny current flow through the mercury vapour with no starter in circuit (or a faulty starter) which is just enough to produce a faint glow visible in a dark room but I'm thinking in terms of older fluoro tubes, not so sure about the newer 'slim' tubes which are notoriously harder to 'strike'.
loopyloo (30-10-17)
No the tubes look ok, used but ok.
I know the tubes and starters work cos I tried them in a different light fitting.
Might let the glue do its job overnight and check it out in the morning.
The glue did the trick.
The tombstone obviously lost contact with the tube.
Both lamps are working now, although slow to start, so I will replace the old lamps and starters.....Job done.
Well done
loopyloo (30-10-17)
He he yeah thanks. Funny how a really simple circuit can be a pain in the butt sometimes. I probed the whole circuit and it was fine. That's why I wondered about the ballast, but when I read 300ohm I though it should be ok too. Well I couldn't probe the tombstone when the fluro was fitted and of course that's when the tombstone spread apart and lost contact.Well done
Anyway, Humbrol plastic model glue worked well and the fitting is as solid as new now.
tristen (30-10-17)
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