Fluorescent light and starter question.

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
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On 20/04/2018 18:51, T i m wrote:

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.
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Adam

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On Fri, 20 Apr 2018 21:04:20 +0100, ARW

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.
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On 20/04/2018 21:25, T i m wrote:

Voltage drop to the house?
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Adam

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On Fri, 20 Apr 2018 21:55:35 +0100, ARW

<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 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.
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On Saturday, 21 April 2018 07:35:03 UTC+10, T i m wrote:

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.
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On Sat, 21 Apr 2018 00:31:21 -0700 (PDT), snipped-for-privacy@gmail.com wrote: <snip> >I would suspect things around choke. Clean and reconnect the terminals. Sometimes cobweb or cockroach muck could cause change in voltage across the choke.
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
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On Saturday, April 21, 2018 at 5:43:15 PM UTC+10, T i m wrote:

Sometimes cobweb or cockroach muck could cause change in voltage across the choke.

oke drop and the plasma drop. Plasma energy is generally low, hence choke i s the component taking most enrgy. Choke may develope intermittency due to failing insulation.failing insulation.

Just to make it clear to you- the plasma breaks due to high voltage induced due to choke in series with t he starter which breaks the circuit to cause it; before plasma breaks tube a high resitance in series with the choke. For your info I am not in Thailand or some stinking Thames river country, I am in Australia a clean intelligent country where early convict arrivals h ave long been dead!
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On Sat, 21 Apr 2018 22:41:11 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

Ok ...

Ok?

So no roaches there either then?

Ah, hence the thought re spiders living in your lights, interfering with the inductance. ;-)
Cheers, T i m
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On Sunday, April 22, 2018 at 5:35:35 PM UTC+10, T i m wrote:

s. Sometimes cobweb or cockroach muck could cause change in voltage across the choke.

choke drop and the plasma drop. Plasma energy is generally low, hence chok e is the component taking most enrgy. Choke may develope intermittency due to failing insulation.failing insulation.

h the starter which breaks the circuit to cause it; before plasma breaks tu be a high resitance in series with the choke.

,
ls have long been dead!

Ah, hence the thought re spiders living in your lights, interfering

Matey! one can survive with spider stings but has no such chance with plagu e from rats in Thames bank;-)
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On 20/04/2018 22:34, T i m wrote:

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

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On Sat, 21 Apr 2018 08:31:30 +0100, ARW

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

Oooerr!
No use for my 70W tubes then. ;-(
Cheers, T i m
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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.

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Andrew Gabriel
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On Sat, 21 Apr 2018 07:49:08 -0000 (UTC), snipped-for-privacy@cucumber.demon.co.uk (Andrew Gabriel) wrote:
<snip> >> Well, that's the sort of thing I am open to but if I understand it

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. ;-)

<snip>

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
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On Sat, 21 Apr 2018 07:49:08 -0000 (UTC), snipped-for-privacy@cucumber.demon.co.uk (Andrew Gabriel) wrote:
<snip> >So a starter for an old 80W tube might not work on a current 70W tube.

I asked a mate if I could borrow a 4-80W starter (thinking he'd have a spare) and he went out and bought me one, a 4-65W.
Anyroadup, I thought I'd give it a try and it seems to work fine so far but I'd have to see how long it lasts to be fair to the questionable ones (as they may have run for a week before the issues started).
Cheers, T i m
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On Friday, 20 April 2018 22:35:03 UTC+1, T i m wrote:

no. There's far too much margin for that.

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On Friday, 20 April 2018 21:25:10 UTC+1, T i m wrote:

the starter is faulty. It should never interfere once the tube is lit, at l east after the first 2 seconds or so. Unless the tube is absolutely on its last legs, which you'd see by increasinly severe flicker every so often the n the starter kicks in. Then it runs ok for a bit then goes into flicker ag ain.
NT
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On Sat, 21 Apr 2018 03:02:11 -0700 (PDT), snipped-for-privacy@gmail.com wrote:
<snip> >the starter is faulty.
Well, 3 of the 6 could be considered so as they fail to even start the tubes from cold but the first two that caused the tubes to flick off now and again, may just be considered 'under spec' ?

Agreed.

Ok.

New tubes (now) so not that in this case.
And that's the ting ... I've been installing and maintaining such fittings for many years now and it's not the first time in the 20 years (or whatever) those fittings have been in the kitchen that one has started to misbehave and I've had to sort them.
The first and obvious trick is to swap stuff about between the two fittings, and / or just pull the starter once the tube is on etc.
It was just I was interested to find out what could cause a potentially good / new starter to start to misbehave but only after (it seemed) a few hours.
Now I'm a little clearer how the system works (thanks Andrew) I can see how a 70W tube could be 'pushing' a starter marked 4-80W (as it's actually likely to be rated as a 4-65W).
I'll put them back in and note the supply voltage when they are working fine and when they aren't and see if there is any correlation (when I believe there is more chance of them misbehaving if the input voltage is low).
All for the S&G's etc.
Cheers, T i m
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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
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On Sat, 21 Apr 2018 08:32:33 +0100, "Brian Gaff"

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
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