Fluorescent light and starter question.

[T i m]

Hi all,

So, I have a couple of 6' single TL-D 70W tube fittings in the kitchen and the other day one started flickering.

I had a box of new tubes so replaced them both (they were due anyway) but one still wasn't right. I found a spare starter and replaced the iffy one and all was well.

I ordered a cotchel of 4-80W basic starters cheap from ebay and when they arrived, replaced both in the fittings and initially all seemed well.

Then a couple of evenings later the Mrs reported one was randomly blinking off and then seemed to do so nearly constantly. Replacing that starter with an old Philips 70-125W one had everything stable again ... until, the other new starter fitted lamp started blinking off. ;-(

So, I bought a small cotchel of electronic starters, replaced the kitchen ones again and they have been fine ever since. ;-)

So, after running the situation past the eBay seller of the first starters we have been having a discussion where he seems to think that it could be anything but the starters ... and I think it could be that the starters are a bit underrated ... and so the range of voltages seen across the starters are sometimes too much for those particular items and hence why they are re-triggering, even when the tube is running fine?

So panel, anyone experienced anything like this before and what was it? Is it just that 70W is on the upper end of a starter rated as

4-80W, especially a cheap one?

One of the same two starters runs a 40W tube / fitting fine.

To add a bit more fuel to the fire. I thought I'd also test the other

4 new starters on the tubes when they were cold. The first caused the tube filaments to glow but the tube didn't even try to start. The next two caused the tube to try to start but not actually manage it. The last did allow the tube to fire up, as then did the previous two but once the tube was already warm?

Putting one of the electronic or one of the old Philips 70-125W starters back in will start the same tube from any situation.

Now, What *I* think might be happening (on the first two new starters at least) is they initially start and run the tubes (two separate fittings) ok until everything warms up, when the voltage across the tube increases slightly, causing the starter to re-trigger and the tube to blink off and back on again. This process is fairly repeatable (it might vary between fittings) and the blinking get's worse if left.

Is it just duff (weak) starters or *could there* be something else?

Cheers, T i m

[ARW]

Remove the starter after the tube is lit and see what happens. The starter is a one shot process. Once the tube is lit it has no further use.

[T i m]

It works fine till you turn it off again. ;-)

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).

Agreed.

Cheers, T i m

[1] The diffusers yellowed and the end plastics went brittle so I may have bought new (slimline) fittings (Fitzgerald?) somewhere along the line.

[ARW]

Voltage drop to the house?

[T i m]

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.

[The Other John]

From Collins Dictionary:

"cotchel

New Word Suggestion:

A large meal or large portion of food. Additional Information possibly from the days of Covent garden fruit market when left over fruit was taken home by workers - eg. taking home a cotchel of fruit."

Are your lights eating starters? :)

[Graham.]

A tranche of starters?

[T i m]

I'd go more with:

'a small quantity'. ;-)

If they are they aren't having currents for pudding. ;-)

Cheers, T i m

[Brian Gaff]

The spread of tolerances in the starters is far too wide I think. Either that or they are marked incorrectly for the job you put them to and all kinds of random changes will then cause issues. Probably knock offs made in a Chinese dodgy plant. Brian

[gopalansampath]

I would suspect things around choke. Clean and reconnect the terminals. Som etimes cobweb or cockroach muck could cause change in voltage across the ch oke. As a total unit, once the plasma is struck the total energy is sum of choke drop and the plasma drop. Plasma energy is generally low, hence choke is the component taking most enrgy. Choke may develope intermittency due t o failing insulation.failing insulation.

[ARW]

Just had a look on the van (I keep starters). Well the first one I picked up was rated 4-65W and 80W!

[Brian Gaff]

Obviously, but that is hardly an answer to the problem but might help you keep fit if you like step exercises!

The fact that the voltage is still enough to operate the starter still points to the spec being incorrect for the job. Brian

[Cynic]

I wouldn't fanny about like that. Buy an led tube with dummy starter and forget the flickering.

[T i m]

I did have a look in one of the two units (that are behaving similarly) and it was as clean in there as when I installed it from new (you don't live in a seedy restaurant in Thailand do you)? ;-)

That would have to be on two independent units then? Not impossible of course but at the same time after maybe 20 years?

Cheers, T i m

[T i m]

Quite.

I agree Brian. I believe the spec (4-80W) should be good for my 70W tubes so it could just be that they are weak units.

It was suggested that along with the gas used in the starter capsule, the initial distance between the electrodes can also set the strike voltage?

Cheers, T i m

[T i m]

I thought you might (and thanks for looking). ;-)

Oooerr!

No use for my 70W tubes then. ;-(

Cheers, T i m

[Andrew Gabriel]

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

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. 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).

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.

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).

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

[T i m]

That could be more the case with these 4-80W jobbies than the 70-125W version.

I think is the right answer.

And you could be right with that as well as they were less than a pound each, delivered (from the UK though).

Cheers, T i m

[harry]

The resistance between the filiments is near infinity when "Off" and near zero when the tube is running. This the basic problem.

The "choke"/inductors provide the high voltage jolt to establish the "arc" between the filiments and then limits the current when running (hence "choke").

Chokes are very reliable. If it goes wrong, you'll probably be able to smell it. (They can also go open circuit) As someone else has said switch the thing on and remove the starter and observe. If it starts to flicker, the tube is at fault (may take some time).

Both tube and starter have sub-atmospheric gas filled glass bulbs. (Plus mercury in the tube) The common fault is for air to leak in. The other fault is for a filiment in the tube to go open circuit.

A fluorescent tube with electronic "choke" is as efficient as an LED bulb.

[T i m]

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

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

Interesting, thanks.

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).

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)?

LOL ... crazy eh, as you say.

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