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The dangers of instant start

The dangers of instant start

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Shame on me. :(

Those of you who view my photos know that out of my dozen or so fluorescent light fixtures, all but two are instant start. Such is life when your specialty is battery powered fixtures. Now, I'm well aware of the detrimental effects of an instant start ballast on fluorescent lamps. Luckily, I have an ample supply of lamps with one or both cathodes broken to run in my instant start fixtures.

But I never knew how quickly an instant start ballast can inflict it's harm on a lamp. Here we have my Norelco F8T5/33, the original lamp that came in the Burgess Safari Lite . It's one of only three vintage lamps I own, one of only two that's 100% healthy, and my only 8 watt lamp with both cathodes intact. See that black blotch below the etching? That happened when I ran it ONCE, for about FIVE SECONDS, on an instant start ballast.

It's a complicated story, but to summarize it, I wanted to compare the current draw of a healthy 8 watt lamp compared to a flickery near-EOL one on the same instant start ballast. I wanted a 100% healthy lamp to compare with, which left me with this one. What harm could it do, right?

Well, I threw this lamp in the instant-start fixture, turned it on, and it started right up. Then there was a bright pink glow for about a second on this end of the lamp, and I was left with this nice blotch.

At the moment I'm running this lamp back in the Safari Lite to try and clear it up. I can't help but feel slightly bad. How does a perfectly healthy lamp go so haywire on an instant start ballast so quickly?

IMG_3279.JPG IMG_3183.JPG IMG_3173.JPG IMG_2997.JPG

Light Information

Light Information

Manufacturer:Norelco (Philips)
Model Reference:F8T5/33
Lamp
Lamp Type:F8T5
Electrical
Wattage:8
Optical
Color Temperature:4300K
Physical/Production
Factory Location:Holland
Fabrication Date:Q2 1972

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Album name:themaritimegirl / Fluorescent lamps
Keywords:Lamps
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Date added:Mar 04, 2013
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TL8W
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Mar 04, 2013 at 07:05 PM Author: TL8W
Made second quarter of 1972.

We do not have to agree on anything to be kind to one another. The ability to be civil is available to everyone on earth, for free.

themaritimegirl
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Mar 04, 2013 at 07:13 PM Author: themaritimegirl
Thanks! I had guessed it was from 1972.

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jercar954
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Mar 04, 2013 at 07:43 PM Author: jercar954
Are you sure it's not mercury condensation?

Preheat and T-12 fluorescents forever! Down with LED's and instant start T-8 fluorescents.

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Brian TheTellyman
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Mar 04, 2013 at 07:43 PM Author: BG101
I've ruined a few good lamps in these horrid battery-powered lanterns too, unfortunately. Usually the blackening burns off to a degree when the tube is run at its correct rating but it's not nice to have a pristine tube blackened like this

Jercar, our posts crossed in the ether I have a few tubes which exhibit significant mercury condensation. I didn't know what it was at the time.


BG

Say NO to DICTATORSHIP in the form of bulb/tube/ballast bans !!

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Mar 04, 2013 at 08:36 PM Author: themaritimegirl
Does the event I describe sound like it could be mercury condensation? It was very strange - the lamp started, then went bright pink at this end like it was EOL, and during the second or two it was pink I watched the black spot grow very fast, just like watching a match burn a whole in a piece of paper. It's been running in the Safari Lite for a couple of hours now, and it looks like it might have faded a little bit, but it's still very visible. That's the last time I ever put a vintage lamp in one of my instant-start fixtures.

Perhaps I'll expand on the summary of the "experiment" that caused this. So my only instant-start 8 watt fixture, one of those crappy GE closet lights, recently kicked the bucket. I've been wanting something to run an 8 watt cathodeless lamp I have to death so I can get rid of it. So, I tried a GE 6 watt closet light I have. It actually worked well - it's meant for 6V, but it takes 12V like a champ, and allows it to start larger lamps effortlessly. It actually started an F17T8 I wired into it.

Anyhow, I tried a couple of 8 watt lamps with one good cathode in them, and they all acted like this one. They started, acted like EOL for a moment, then ran fine afterwards. Those lamps never acted like that before, so I'm wondering if because I'm running that fixture at twice it's rated voltage, if it's OCV is so high that it's simply beyond what any small fluorescent lamp was designed for, thus causing the arc to go nuts upon start-up?

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dor123
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Mar 05, 2013 at 05:51 AM Author: dor123
Don't confuse between a mains voltage instant start electronic ballast, to a battery operated instant start emergeny inverter.
Even if a two wires IS ballast, have no any heating supply to the electrodes at all (Unlike most of the 220-240V 4 wires IS ballasts), if the lamp operates at the electrodes thermionic emission temperature (By the discharge, similar to LPS and HID lamps), so the electrodes will be hot cathodes and will almost not sputter during operation, but only during starting.
However, if the lamp operates with an IS two wires emergency inverter (Which often underdrives the lamps [Occurs also in several american mains voltage electronic IS two wires ballasts]), the electrodes willn't reach the thermionic emission temperature, so the electrodes will be cold cathodes, and will sputter very fast, resulting in an end blackening from only several minutes of operation.

I"m don't speak English well, and rely on online translating to write in this site.
Please forgive me if my choice of my words looks like offensive, while that isn't my intention.

I only working with the European date format (dd.mm.yyyy).

I lives in Israel, which is a 230-240V, 50hz country.

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Mar 05, 2013 at 11:49 AM Author: themaritimegirl
Yes, I know all that. I don't think it's due to being underdriven because I've never seen a lamp do this simply because it was underdriven before. I'm waiting for someone with more technical knowledge than myself to confirm or debunk this, but I'm thinking that because I ran this lamp on a fixture designed for 6V input, running on 12V, that the OCV was just too high for what a lamp of this size is supposed to handle.

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BG101
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Brian TheTellyman
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Mar 05, 2013 at 07:30 PM Author: BG101
One possible outcome of running the lantern at this voltage is to distort the waveform produced by the oscillator, which could heavily bias the tube or produce potentially harmful spikes (assuming it's not already) .. the other is the power dissipation by the transistor. I'm amazed it hasn't already melted the casing! I know this from experience ..

My mods of this sort of circuit involve a higher-rated transistor, a couple of resistor changes and, with one exception, a decent heatsink.


BG

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Mar 05, 2013 at 10:53 PM Author: themaritimegirl
Makes sense. Yeah, it actually ran pretty cool while I was doing this!
By the way, I sent you a PM slightly related to this.

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Mar 08, 2013 at 10:30 AM Author: don93s
I've had many new lamps make spots within minutes to hours on preheat or rapidstart fixtures. My theories are either the lamp is either burning off impurities or the emitters are not perfectly distributed on the filament wire. Another case might be too high of crest factor which could happen with a cheap "electronic" ballast that isn't working properly. An instant start fixture could possibly exacerbate any of the above problems, imo.
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