Both tubes in a flourescent are flickering and won't light. Reading up on the symptoms suggests the ballast at fault but there's two of them so unlikely they've both failed?
As the only thing in there that there's only one of is a capacitor, is it likely to be that at fault?
If you have any other tubes of the same type change one and see what happens. I'm assuming these are the standard starter type old school fittings, like the old Thorne ones for example. I thought the capacitor was all to do with power factors and all that? Brian
I had a twin fluorescent unit that flickered a bit for all of its life. I recently fitted LED retrofit replacement tubes and I am delighted with the result. You do need to know whether the ballast is magnetic or electronic as there are different versions.
I seem to recall my posting creating a surprising level of controversy in this group.for some obscure reason.
Some systems have the tubes in series.
Remove the cap and see. It does sweet FA regarding the lights actually ability to work. A duff one could cause problems. It's only there for power factor corrections.
Or swap the lamps for LEDS ones and bypass the ballast and the capacitor.
That's quite common in dual 2' fittings, although not all work that way. The two tubes in series type require different rated starters too. When one tube dies, the other will stop working too.
Quite - this is the concept of series :-)
Maybe they are making a cake?
Christ, what a palaver I seem to have provoked!
Don't blame yourself. The "palaver" was largely the result of a "Rod Speed baiting frenzy" by Fredxxx and tabbypurr most of which I swiftly passed by unread (I did briefly consider killfiling both perpetrators but, hey! it was a Rod Speed baiting exercise after all and he's already in my killfile filter). :-)
Your post did give me cause to track down my "Lamps and Lighting" book (1972 edition) to check out fluorescent ballast circuits but I didn't see any twin tube switch start circuit examples (only one each of the Quickstart , Rapid-start and cold-start transformer circuits, each sans any 'starter switch').
I'm pretty certain the total of 14 fluorescent ballast circuits shown in the book are far from an exhaustive list but I can't think where else I may have seen a more comprehensive one.
Perhaps your twin tube fitting is simply two independently ballasted switch started lamps wired to a common PFC capacitor? Does the fitting use two plug in starters? Also, does removing one of the lamps prevent the remaining one from even starting up or else modify the flickering symptom if it does still light up?
It's quite possible that it's just a case of both lamps wearing out at almost the same time. The second lamp to start flickering may well have masked the flickering of the first lamp failure giving a false impression that both lamps have either improbably failed simultaneously or else the problem lies with another common component.
Having checked out what wikipedia has to say on the subject (not as much as I'd hoped) and a google search, I did see a few examples of twin tube fittings using switch starting where a couple of 2 foot 20W tubes are connected in series via a single ballast choke to the mains supply using two starter switches, one for each tube. To my mind, a rather improbable circuit but since I saw at least three examples of this twin tube circuit, I guess it must exist IRL.
If your fitting is using the same arrangement, it will be blessed (or cursed) with *two* starter switches. Also, this means that removing any one tube will cause the remaining tube to stop working (they are in series). The presence of a starter across each tube must make for an unusual starting sequence under normal working conditions (there's going to be some interaction between the operation of each starter switch).
It seems that the flickering of *both* tubes only requires one of them to go faulty, loss of emmissive material at a cathode, either from old age or from premature failure. BTW, I can't figure out how a *single* starter can be wired up to start a double tube fitting. If you've already tried replacing "the starter switch", singular, I reckon you must have missed one.
The problem could be as simple as a single tube failure. However, in view of the liklihood of it being age related wear out, I'd suggest replacing both tubes, keeping hold of the old but still working tube as a spare for diagnostic testing purposes the next time one of the tubes starts exhibiting such symptoms (often the result of being used way beyond its useful 8,000 hours or so service life typical of use in switch start circuits - 16000 hours being more typical with modern delay start electronic HF ballast units).
En el artículo , R D S escribió:
A killfile works wonders. I saw only five posts out of the 130 in the thread, including yours.
We tried to introduce him to reality on his own terms, a futile exercise.
you need a better book!
what other info did you hope to find?
it was moderately common. A definite compromise but cheaper.
yeah, it's a bit crazy to watch. But it gets there.
could be either tube bad, either starter bad, or a bad connection somewhere. That's the main downside of 2 tubes on one switchstart ballast.
I don't believe it can
NT
Given the 4 heaters need preheat to strike, I don't believe you can have just the one starter either.
It might have been smarter to have killed the whole thread.
But then you won't see this!
Practically, no. If desperate one could make it work with only 2 getting preheat, but it wouldn't do tube life any good.
NT
The point I was making was that the OP only mentioned trying a replacement starter (*singular*) which implied some cunning circuit topology where both tubes could be started using just a single starter switch. However, once you've resorted to that sort of complexity, a starter becomes redundent since you're now into the territory of twin tube quickstart and rapidstart ballasts which can fire up the tubes without any such switch starter devices.
Rather than speculate any further, I'll await the OP's response to clarify the situation for us. I'm anticipating that he'll confirm the use of a pair of starters and that the unit won't even attempt to light up either of the remaining tubes once one of them has been pulled from the fitting.
Of course the OP requires 2 starters, unless it's a cobbled together fitting of different ballast types, or some homebrewed oddity.
You can start 20w tubes by simplifying the setup rather than complicating it... just remove the starters & use an LC ballast instead of L. The resulting raised starting voltage slowly increases tube current until it lights properly. Done that before.
NT
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