Fluorescent tubes and starters

[Brian Gaff]

I honestly do not think the few flickers at start is the cause of failure particularly. I've had them last for ages in lights that flicker at the start. One thing that does cause a lot more flicker seems to be low temperatures. For some odd reason some tubes like it warm or take an age to start or never do so. This seems to afflict the thinner ones, which is counter intuitive to me. There used to be quick start ballasts around that did not use starters and these seemed to be better to me. Brian

[DerbyBorn]

My observation is tha tthe DIY Sheds tend to sell rather conventional outdated fittings - and they have little information on the diplay. I guess one needs to go to a proper electrical wholesaler.

Noticed this week - some interesting LED replacement for tubes, They had a plat white panel about a foot deep - some light escaping from the side faces of the panel - and most emerging through the panel and out of the bottom face. They seemed very effective.

Also in local Walmart - all tubes replaced with LED arrays. At first sight

- they look the same - but focus your eyes and the individual LEDS are apparent.

[Johny B Good]

Actually, I _did_ do a dummy run on the checkout page (it was a lot simpler than some I've used) and there are TWO surprises. The first being the expected P&P item with the second being the VAT. Even so, it only came to a total of just £4.38 incl P&P plus VAT.

[Tim Streater]

Well, according to Winky that does have lot to do with it, because with the rubbish starter I've got at the moment, it flickers like that each time we turn it on. As it's in the utility room it gets turned on/off quite a lot. Each start tends to sputter off some of the cathode material. They reckon using an electronic starter extends the life quite considerably.

[meow2222]

Switchstart gives around half the tube life. Electronic, thermal & manual start give better life - though there are electronic ones that dont.

NT

[Andrew Gabriel]

I still have an SRS set of gear and a tube somewhere, although not connected together.

Mine's the first edition, 1966.

I just stripped out 3 85W Transtar ballasts from my parents' living room pelmet lighting, and replaced with dimmable T5's. The Transtars were probably quickstart, but you can't see as ballasts, transformers, capacitors, etc are all expoyed into a a large can.

My bedroom in my parents' house still had a dimmable ballast I made nearly 40 years ago for the 5' 80W tube until they refitted the room as an office a couple of years ago.

They still have a couple of 5' 80W tubes with bayonet cap ends and 4-pin starters lighting the loft.

They generally work on constant current, so that one ballast can operate several tube lengths in the same family.

More modern ones have a microcontroller which can work out which of several different tubes are fitted from different families, and operate each of them correctly. This significantly reduces the number of different ballasts which have to be manufactured and stocked.

I wish that was true, but electronic ballasts are still much more expensive than they should be.

[meow2222]

I studied Atkinson's 1947 book.

Much nicer to live with than glowstart

NT

[Andrew Gabriel]

Isn't that the phone and exchange wiring book?

They are glowstart. The thermal starters took much longer to start the tubes.

[Johny B Good]

Probably using the QuickStart transformer plus ballast or its equivilent, a high leakage transformer. Essentially, the transformer was an autotransformer with 10v or so taps from each end to preheat the cathodes wired across the tube.

Prior to the tube striking the transformer would see nearly the full mains voltage until the tube struck wherupon the voltage would fall to around the 108v mark reducing the heater current with the mercury arc current providing the majority of the heating effect as per the usual modus operandi.

The cathodes would still run warmer than on a switch start circuit but this was to the benefit of the life of the tube since it reduced the risk of cathode stripping due to marginal electron emission causing a damaging ionic current flow to make up the difference.

These were in common use in UK telephone exchanges throughout the 70s and 80s.

[Johny B Good]

As does the quickstart transformer. Until the advent of electronic ballasts, this was the "Rolls Royce" of fluorescent lamp running gear.

If you only switch a cheap switch starter lamp on once and leave it running it can last as long as 2 or 3 times its rated life (these days, rated life is up to 16,000 hours, about twice what it used to be around 1980).

It's only when you are switching it on and off frequently that the wear and tear of a switch starter takes its toll on the cathodes. The quickstart ballasts allow you to apply far more switch on cycles per day without the detriment exhibited by the cheap switch starter ballasts.

The near instant (less than 200ms) startup to full light output encourages you to switch them on and off for even the briefest of moments so it's just as well that they don't inflict anywhere near the wear and tear of a switch starter.

If you want a quick fix, the electronic starter switch is a quick 'n'dirty solution to the issue of high startup wear on a frequently switched conventionally choke ballasted light fitting. You won't get the improved efficiency of an electronic ballast though, just extended life from your tube(s).

[sm_jamieson]

I put those in the kitchen. You get a hurrrrumph sound as they start but th ey are quick. The pre-heat ones with 2 seconds delay would not be accepted by the family, even if the delay was explained ! I gave up on electronic ballasts for my use - the unshielded installation a bove the kitchen units radiated and blocked out FM radio in the room ! Might be OK in an earthed metal enclosure, although the enclosed "luminaire " in my mothers utility room certainly interferes with radio 4. Simon.

[meow2222]

Here it is, Fluorescent Lighting by A.D.S. Atkinson AMIEE, 3rd edition 1948. Most of it was still right until T8s came along, but there is the odd oddity.

He reported choke power losses as:

12w for 40w 4ft tube 10w for 80w 5' tube And the lumens/watt as 38 for 5', 43 for 4', despite calcium halophosphate being on the list of phosphors, though the main one used was apparently zinc sulphide plus metal activators.

I so much preferred the thermals. You can also use a relay with simple RC delay, but the 50Hz choke days are nearly gone now.

NT

[Andrew Gabriel]

OK, it probably predates the change with the UK reducing 5' tubes from 80W to 65W (and 6' tubes from 85W to 75W).

We originally designated the 5' tube as 80W because it could then use the same ballast as an 80W mercury vapour lamp, which already existed. That's also the same reason we went with baynet caps - they already existed and tooling up to make something new during the war was to be avoided where possible.

I don't know the date, but shortly after the war, we changed the

5' tubes to 65W which is the most efficient rating for that tube length at the time, and what the US were using by then.

Through to about 1980, 5' tubes were mostly dual rated 65/80W so they could be used in old or new fittings (and same for 6' 75/85W).

[meow2222]

n 1948. Most of it was still right until T8s came along, but there is the o dd oddity.

ate being on the list of phosphors, though the main one used was apparently zinc sulphide plus metal activators.

According to his book, only 4' 40w and 5' 80w tubes existed. IIUC 4' were b ipin from the start, 5' were still BC only then.

He does also mention that some smaller tubes had been proposed: 3'30w T8, 2 ' 20w in T8 & T12 versions, and 1.5' 15w T8. So it seems 6' didnt exist, an d perhaps hadn't even been proposed then. If that's not the case it would b e an odd omission. Bear in mind the dates:

1st edition 1944 2nd 1946 3rd 1948 So it seems unlikely he'd be out of date.

I guess the 2' T8 never came about, at least not till another several decad es.

Oh, and he reports average tube life as 3000 hours. And makes it clear that glowstarters don't switch more than once at powerup, that if they ever do the thing is faulty, and should be taken out of service until fixed.

Very high tech compared to carbon arc & carbon filament lamps, both of whic h I've used.

NT

[Andrew Gabriel]

Electronic starters come in different types. Some very deliberately try to strike the tube very quickly, way before the filaments are preheated, and will give short life for frequent switching. Others deliberately go for > 2 seconds preheat, and will give long life with frequent starting. The instant starting type usually create a rather loud buzz from the ballast whilst starting, because they're generating a back-EMF voltage spike every mains cycle to start the tube as a cold cathode tube, whereas the preheat type heat the electrodes (for typically 2.3 seconds), and then let the tube strike in thermionic emission mode using just mains voltage and avoid generating any high voltage pulse.

Glow starters work very well on UK mains voltage (pretty much max life) for 4' and 5' tubes, but work very badly on US mains voltage (where they can only work on short tubes anyway), which is why you will see them often stated as giving short tube life. They don't work so well for shorter tubes on 240V mains because the tube can strike before the filaments hit thermionic emission temperature, causing a short period of cold cathode operation which wears the electrodes very quickly for a second or two at start.

With infrequent starting, the type of starter and control gear make almost no difference to tube life. Stated tube life is based on 3 hours on-time per switch-on.

It used to be possible to buy electronic control gear which is instant-start (i.e. < 0.1 seconds), but they have got much harder to find. I used them in places like bathrooms where you don't want to have to wait, and also in my garage where we nip in and out very quickly (probably within 5 seconds) to grab something from the freezer. Even the Philips Matchbox range for small tubes, which come in instant start or preheat versions - the current instant start ones are no longer instant, whereas they used to be. Sometimes you want instant start over long tube life.

[meow2222]

The only bit I'm puzzled about is this

IME glowstarters nearly always repeatedly try to start the tube prematurely, regardless of tube length, so life reduction seems inevitable.

Atkinson says that wasn't the case in the 40s. I'm guessing miniaturisation to save cost has resulted in them switching faster in more recent decades.

NT

[John]

Most of the tubes at Church are the old T12 (I think) ones. Some of the fittings have starters, some do not.

I am told that the old, fat tubes are no longer available. I have heard scare stories about using the T9 tubes in old style fittings.

Any tips, real warnings, etc. - do not want to have to replace a load of fittings.

Thanks

[meow2222]

Simple, use T8s all round. Same light for less power. Its unlikely you'd encounter fittings that wont work with them, though they do exist. There's nothing to worry about.

NT

[John]

Thanks - scare stories abound!

[Andrew Gabriel]

The common UK tube sizes cannot strike in cold cathode mode with just mains voltage, but can strike in thermionic emission mode with just mains voltage. The glow starter alternately heats the filaments and leaves the tube to try striking. The tube will fail to strike until the starter has heated the filaments to thermionic emission temperature. A failed strike may not look pretty, but doesn't harm the tube. Harm is done by any successful premature strike.

I'm not aware of any significant change in behaviour (in UK ones) since I've known them. In the US, they've played with all sorts of different gas mixtures and radioactive doping to get combinations which work well with the 120V mains, but that's not a problem we have on 240V mains.