Problem with fluorescent lights (2 tubes in series).

[Victor Roberts]

Ahh! Sounds like someone who can answer a long standing question.

Background:
I understand the older switch start system. You need something like 500
volts to start the tube discharge, the ballast inductance keeps the arc
going (My mental model).

Only instant start lamps need voltages near 500 volts. Rapid Start and
Switch Start lamps have heated electrodes and can start with much
lower voltages. I believe the starting voltage for a 4-foor T12 rapid
start lamps is about 230 volts. 2-foot switch start lamps can start on
120 volt circuits with no inductive kick.

The role of the ballast is to LIMIT the current drawn by the lamp. The
arc will keep going quite well without any ballast. In fact, so well
it will burn out in a fraction of a second

So how does the rapid start get started? and what's the interchangeability
between switch start and rapid start fixtures and bulbs?

On a traditional rapid start system the electrode voltage and lamp
voltage are applied at the same time. The lamp voltage is not high
enough to start the lamp while the electrodes are cold. Once the
electrodes heat to operating temperature the lamp starts.

Switch start lamps have higher resistance electrodes than normal rapid
start lamps and can only be used on special rapid start ballasts
designed for these higher resistance electrodes.

 

[Sam Goldwasser]

SO... Is this sorta' like that nifty method of starting a gas laser with a
low current voltage multiplier using diodes & caps in series with the main
supply...and when the tube fires the multiplier diodes are just in series
with the running supply ???

If so, how do they prevent excessive drop across this winding when running
current flows?

It's more like a loosely coupled HV winding.

http://www.repairfaq.org/sam/flamp.htm#wd5

Hi Sam. I sent a laser power supply schematic to you some years ago.

Yes you did. It's still in the Laser FAQ.

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[Adam]

quoting:


No light at all means: open circuit. Wether it's in the ballast,
wiring, lamp holder, lamp filaments, or starter.

If everything else tests good, then I would suspect the starters. In
a duel starter setup in a series configuration, each starter sees a
lower voltage
than they would if it were a single starter. This reduced voltage is
not enough to activate each of the starters if the starters you
installed are
designed for a single starter setup. You will need to get the proper
starters that were designed for your two starter series setup.

Good point. The two starters I took out of the fitting in question are
labelled "220/240V Series 110/130V Single" -- but they do work (one at
a time, of course) in a 230V single-tube fitting.

Nonetheless, starters are cheap, so I'll get some *correct* replacement
ones tomorrow.

Thanks,
Adam

 

[James Sweet]

Good point. The two starters I took out of the fitting in question are
labelled "220/240V Series 110/130V Single" -- but they do work (one at
a time, of course) in a 230V single-tube fitting.

Nonetheless, starters are cheap, so I'll get some *correct* replacement
ones tomorrow.

Thanks,
Adam

Hmm the ones you have sound like they are the correct ones, wouldn't hurt to
try some new ones though.

 

[AC/DCdude17]

X-No-Archive: Yes

If you post on sci.engr.lighting there are some very good experts in this
type of thing.

I would try another ballast, if I know that the wiring is good. Testing it
with an ohm meter is not a very good test. If there are any defect, you have
no good way to know with an ohm meter.

There are some new electronic ballasts that don't require starters. These
are worth the investment.

Actually, the ballast only act as a current limiter the moment power is
applied. The glow starters in this setup is completely dependent on line
voltage and if the ballast isn't open circuit, both will glow.

These should explain why nothing is happening.

1. Wrong starters with same physical connector. Just because they fit do not
mean they're right.

He mentioned he pulled starters from different fixtures. If those working
fixtures only took one lamp, the starter will have a higher break down voltage
than a starter used in series connected application.

2. Connection error/problems

3. Broken filament(s) in one or both tubes.

4. Failure in hermetic seal on one of the starters.

 

[Adam]

Thanks for all your suggestions, especially JM who came up with the
right answer in my case: replace the starters with the correct ones. I
had tried good 240V starters where I needed 120V starters. I bought
and installed two new 120V starters and the lights came on. Then I put
the original (two-year-old) tubes back in and they worked. (So now I
have spare tubes.)

This leads to me to ask a few extra questions.

1. Tubes and starters are both consumables, but isn't it unusual for the
original starters to fail before the original tubes? (My experience
has been that tubes need to be replaced more frequently than starters.)

2. Why did the failed 120V starters work in a single-tube 240V fitting?

3. Would it have been hazardous to leave those starters in use at 240V?

Thanks,
Adam

 

[soxlamp180w]

Hi Adam

The starters may be the wrong ones

You need 155/100, 155/200 or Osram ST 151 types as they operate on 110v
single or 240v series

Soxlamp180w

 

[soxlamp180w]

Hi Adam

This leads to me to ask a few extra questions.

1. Tubes and starters are both consumables, but isn't it unusual for the
original starters to fail before the original tubes? (My experience
has been that tubes need to be replaced more frequently than starters.)

some starters can last for many years before failing although Lamp suppliers
do recommend them to be replaced at the same time as the tubes

2. Why did the failed 120V starters work in a single-tube 240V fitting?

The voltage is twice the amount and as the starter gets older the contact
between the Bi metal strips in them spreads wth age and as the voltage is
increased from 120V to 240V the spark gap operated without any problems

3. Would it have been hazardous to leave those starters in use at 240V?

No as they are designed to be used on both 120v and 240v but if you fit a
new 120v Starter in a single fitting the bi-metal strips do seperate faster
and will affect the life of the tube as they will cause it to flicker for a
few times before striking the arc and if you decide to use the same starter
in a twin tube light it may not work as the bimetal strips have spread too
far


Hope this helps

Soxlamp

 

[Adam]

Hope this helps

Interesting -- thanks.

 

[N. Thornton]

Only instant start lamps need voltages near 500 volts. Rapid Start and
Switch Start lamps have heated electrodes and can start with much
lower voltages. I believe the starting voltage for a 4-foor T12 rapid
start lamps is about 230 volts. 2-foot switch start lamps can start on
120 volt circuits with no inductive kick.

The role of the ballast is to LIMIT the current drawn by the lamp. The
arc will keep going quite well without any ballast. In fact, so well
it will burn out in a fraction of a second

So does this mean I could put a 2 foot tube with a capacitor for a
ballast onto a 240v supply and it would light? I did have one standard
L ballast 2' fitting with no starter, and was surprised the thing
would light reliably with some 2' tubes, but not at all with others. I
put a starter in in the end

Regards, NT

 

[Victor Roberts]

So does this mean I could put a 2 foot tube with a capacitor for a
ballast onto a 240v supply and it would light? I did have one standard
L ballast 2' fitting with no starter, and was surprised the thing
would light reliably with some 2' tubes, but not at all with others. I
put a starter in in the end

Regards, NT

No. You cannot use a capacitor as a ballast at 50 or 60Hz. Well, you
actually can, but the current will flow in short, high current spikes,
once each half-cycle and will destroy the lamp electrodes in a short
period of time. You would need either a resistor, which would be very
lossy, or inductor at 50Hz or 60Hz.

 

[James Sweet]

So does this mean I could put a 2 foot tube with a capacitor for a
ballast onto a 240v supply and it would light? I did have one standard
L ballast 2' fitting with no starter, and was surprised the thing
would light reliably with some 2' tubes, but not at all with others. I
put a starter in in the end

The later of those "Brite Stick" fluorescent lights used exactly that, they
ran off 120v though, at least in this country. Early ones had a choke
ballast in an enlarged end, later ones just used a capacitor, there may have
been other passive components but there was no choke.

 

[Victor Roberts]

The later of those "Brite Stick" fluorescent lights used exactly that, they
ran off 120v though, at least in this country. Early ones had a choke
ballast in an enlarged end, later ones just used a capacitor, there may have
been other passive components but there was no choke.

Bright Stick (R), which is a GE Trademark, never used either a
capacitor or inductor ballast. Bright Stick (R) uses a resistor
ballast which is formed from a resistive wire extruded into the
plastic base plate. That is the reason the system is so light. Since
GE had a patent on this design, similar products made by other
companies used a heavy inductor.

As I stated above a capacitor ballast is a very poor choice, A
capacitor by itself would destroy the lamp electrodes in a very short
period of time. Some cheap shop light fixtures use a ballast composed
of a series connected capacitor and a small inductor, with the
inductor designed to reduce the size of the current spike that would
result from the use of a capacitor by itself. However, these LC
ballasts still produce very high lamp current crest factor and hence
result in short lamp life.

 

[James Sweet]

Bright Stick (R), which is a GE Trademark, never used either a
capacitor or inductor ballast. Bright Stick (R) uses a resistor
ballast which is formed from a resistive wire extruded into the
plastic base plate. That is the reason the system is so light. Since
GE had a patent on this design, similar products made by other
companies used a heavy inductor.

Interesting, I distinctly remember seeing a capacitor inside the end cap,
perhaps it served another purpose.

 

[Sam Goldwasser]

Bright Stick (R), which is a GE Trademark, never used either a
capacitor or inductor ballast. Bright Stick (R) uses a resistor
ballast which is formed from a resistive wire extruded into the
plastic base plate. That is the reason the system is so light. Since
GE had a patent on this design, similar products made by other
companies used a heavy inductor.

Must be the World's most inefficient fluorescent fixture. The whole
idea of an inductor or capacitor is that it doesn't dissipate significant
power. But with a resistor, probably over half the power is going into
heating the resistor.

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Important: The email address in this message header may no longer work. To
contact me, please use the feedback form on the S.E.R FAQ Web sites.

 

[Victor Roberts]

Interesting, I distinctly remember seeing a capacitor inside the end cap,
perhaps it served another purpose.

Bright Stick (R) is a switch start system. Every switch start system
(at least in NA) uses a small capacitor across the starter to reduce
EMI. This is not the ballast.

 

[Victor Roberts]

Must be the World's most inefficient fluorescent fixture. The whole
idea of an inductor or capacitor is that it doesn't dissipate significant
power. But with a resistor, probably over half the power is going into
heating the resistor.

Yes, it is rather inefficient. The GE catalog says 725 lumens for 35
watts, which is only 21 lm/W, but it does have a life of 7500 hours

 

[Clive Mitchell]

Interesting, I distinctly remember seeing a capacitor inside the end cap,
perhaps it served another purpose.

It wasn't a starter? The original hand-held fluorescent inspection
lamps that had a resistive lead had a starter in the handle.

 

[James Sweet]

It wasn't a starter? The original hand-held fluorescent inspection
lamps that had a resistive lead had a starter in the handle.

I could be remembering wrong, when I disasembled a dead one I was probably
only 5 years old at the time, so it's been a while.