Problem with fluorescent lights (2 tubes in series).

[Adam]

I have a light fitting that takes two tubes wired in series in what I
believe is the standard configuration. I've replaced both tubes twice
and replaced both starters with ones taken from fluorescent fittings
that work. I've also checked the ballast to make sure it hasn't failed
open (ohmmeter with the power off: 50 ohms) but I understand ballasts
rarely fail. I've gone around it with a voltmeter and an ohmmeter
checking for any other open circuits and all the wiring seems good.
(This is in the UK, so 240VAC 50Hz.)

The only difference is that the original tubes that worked were labelled
"18W/41" and the replacements (available near my house) are "18W/35".
They have the same length and diameter.

Any suggestions?

Thanks,
Adam

 

[Sam Goldwasser]

I have a light fitting that takes two tubes wired in series in what I
believe is the standard configuration. I've replaced both tubes twice
and replaced both starters with ones taken from fluorescent fittings
that work. I've also checked the ballast to make sure it hasn't failed
open (ohmmeter with the power off: 50 ohms) but I understand ballasts
rarely fail. I've gone around it with a voltmeter and an ohmmeter
checking for any other open circuits and all the wiring seems good.
(This is in the UK, so 240VAC 50Hz.)

The only difference is that the original tubes that worked were labelled
"18W/41" and the replacements (available near my house) are "18W/35".
They have the same length and diameter.

When you say: "standard configuration", you mean two tubes with their
filament circuits wired in series, starters across each tube, and ballast
in series with everything? Something along these lines?:


=======
L o---+-----^^^^^^^-------+ +-----+
| Ballast | | |
| (Inductor) +|-|+ |
| | - | |
| | | +-+
| Tube 1 | | |S| Glow Starter
| | | +-+
| | - | |
| +|-|+ |
| | | |
_|_ Power Factor | +-----+
___ Correction |
| Capacitor | +-----+
| | | |
| +|-|+ |
| | - | |
| | | +-+
| Tube 2 | | |S| Glow Starter
| | | +-+
| | - | |
| +|-|+ |
| | | |
N o---+-------------------+ +-----+


What exactly happens? Have you checked with the voltmeter with power
applied? What are the readings?

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[Steve]

The only difference is that the original tubes that worked were labelled

"18W/41" and the replacements (available near my house) are "18W/35".
They have the same length and diameter.

Then they're basically the same tubes, the 41 and 35 relates to the
colour-temperature in x100 degrees kelvin, 4100 and 3500 respectively.

Are you sure both tubes are in working condition. Can you show us how you
wired everything toghether?

Thanks,
Adam

Steve

 

[Adam]

When you say: "standard configuration", you mean two tubes with their
filament circuits wired in series, starters across each tube, and
ballast in series with everything? Something along these lines?:

That's the one, although the ballast is on the neutral side rather than
the live one.

What exactly happens? Have you checked with the voltmeter with power
applied? What are the readings?

I took the tubes and starters out. I used the ohmmeter with the power
off to make sure that there aren't any breaks in the wiring (by
applying the probes to various points such as the contacts in the tube-
and starter-holders). Then I used the voltmeter with the power on to
test that the power is connected properly. All the measurements failed
to produce any evidence of breaks.

 

[Adam]

Then they're basically the same tubes, the 41 and 35 relates to the
colour-temperature in x100 degrees kelvin, 4100 and 3500 respectively.

I thought the second number meant something like that.

Are you sure both tubes are in working condition. Can you show us how
you wired everything toghether?

Here's the wiring diagram (slightly modified from the other post --
thanks Sam):

L o---+-------------------+ +-----+
| | | |
| +|-|+ |
| | - | |
| | | +-+
| Tube 1 | | |S| Glow Starter
| | | +-+
| | - | |
| +|-|+ |
| | | |
_|_ Power Factor | +-----+
___ Correction |
| Capacitor | +-----+
| | | |
| +|-|+ |
| | - | |
| | | +-+
| Tube 2 | | |S| Glow Starter
| | | +-+
| | - | |
| +|-|+ |
| ======= | | |
N o---+-----^^^^^^^-------+ +-----+
Ballast

I didn't wire any of this internal stuff myself; I just installed the
fitting on the wall, connected the incoming power to the terminals and
put the original tubes in a year or two ago. It worked fine until at
least one tube failed (obviously I understand that either tube's
failure will stop both from lighting) and then I couldn't get it to
work with two new tubes. I took those two back to the store and
exchanged them for two more: it still doesn't work. In the meantime I
swapped the starters with two others from working single-tube fittings
in another room. (The other fittings are still working with the
starters taken from the troublesome one, so the starters must have been
OK anyway.)

 

[Steve(JazzHunter)]

I thought the second number meant something like that.


Here's the wiring diagram (slightly modified from the other post --
thanks Sam):

L o---+-------------------+ +-----+
| | | |
| +|-|+ |
| | - | |
| | | +-+
| Tube 1 | | |S| Glow Starter
| | | +-+
| | - | |
| +|-|+ |
| | | |
_|_ Power Factor | +-----+
___ Correction |
| Capacitor | +-----+
| | | |
| +|-|+ |
| | - | |
| | | +-+
| Tube 2 | | |S| Glow Starter
| | | +-+
| | - | |
| +|-|+ |
| ======= | | |
N o---+-----^^^^^^^-------+ +-----+
Ballast

I didn't wire any of this internal stuff myself; I just installed the
fitting on the wall, connected the incoming power to the terminals and
put the original tubes in a year or two ago. It worked fine until at
least one tube failed (obviously I understand that either tube's
failure will stop both from lighting) and then I couldn't get it to
work with two new tubes. I took those two back to the store and
exchanged them for two more: it still doesn't work. In the meantime I
swapped the starters with two others from working single-tube fittings
in another room. (The other fittings are still working with the
starters taken from the troublesome one, so the starters must have been
OK anyway.)

I think the other posters would like to know "What doesn't work." No
sign of life at all as if there's no power? Or does the filament glow
and nothng else? Or do the tubes flouresce dimly but don't fire to
full brightness? Each one of these scenarios suggests a different
problem.

. Steve .

 

[Jerry G.]

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.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
=========================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
=========================================


I have a light fitting that takes two tubes wired in series in what I
believe is the standard configuration. I've replaced both tubes twice
and replaced both starters with ones taken from fluorescent fittings
that work. I've also checked the ballast to make sure it hasn't failed
open (ohmmeter with the power off: 50 ohms) but I understand ballasts
rarely fail. I've gone around it with a voltmeter and an ohmmeter
checking for any other open circuits and all the wiring seems good.
(This is in the UK, so 240VAC 50Hz.)

The only difference is that the original tubes that worked were labelled
"18W/41" and the replacements (available near my house) are "18W/35".
They have the same length and diameter.

Any suggestions?

Thanks,
Adam

 

[Adam]

I think the other posters would like to know "What doesn't work." No
sign of life at all as if there's no power? Or does the filament glow
and nothng else? Or do the tubes flouresce dimly but don't fire to
full brightness? Each one of these scenarios suggests a different
problem.

Good point, sorry!

There is no light _at_ _all_, although power is present in the fitting
(about 230V measured across the main terminals with the tubes in, and
on the appropriate contacts with the tubes out).

 

[Adam]

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.

True: the only thing I know is that it hasn't failed open.

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

I'll look into that. Can these be used as a "drop-in" replacement for
the ballast in the existing circuit? Then I just take the starers out
and leave their sockets empty?

 

[Sam Goldwasser]

I took the tubes and starters out. I used the ohmmeter with the power
off to make sure that there aren't any breaks in the wiring (by
applying the probes to various points such as the contacts in the tube-
and starter-holders). Then I used the voltmeter with the power on to
test that the power is connected properly. All the measurements failed
to produce any evidence of breaks.

But what exactly happens? First the starters should light up. Then
the starter switches should close. Then the filaments of the tubes
should come on. Then one or both will go out and the tubes should
try to start.

Do the filaments light up? Have you confirmed that the tubes have good
filaments (with the ohmmeter)?

--- sam | Sci.Electronics.Repair FAQ Home Page: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
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| Mirror Site Info: http://www.repairfaq.org/REPAIR/F_mirror.html

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.

 

[Sam Goldwasser]

I didn't wire any of this internal stuff myself; I just installed the
fitting on the wall, connected the incoming power to the terminals and
put the original tubes in a year or two ago. It worked fine until at
least one tube failed (obviously I understand that either tube's
failure will stop both from lighting) and then I couldn't get it to
work with two new tubes. I took those two back to the store and
exchanged them for two more: it still doesn't work. In the meantime I
swapped the starters with two others from working single-tube fittings
in another room. (The other fittings are still working with the
starters taken from the troublesome one, so the starters must have been
OK anyway.)

It's still possible the single tube starters don't have the same
breakdown voltage as the two tube starters. They might be higher.

Get a pair of proper starters and try again.

--- sam | Sci.Electronics.Repair FAQ Home Page: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Site Info: http://www.repairfaq.org/REPAIR/F_mirror.html

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.

 

[James Sweet]

True: the only thing I know is that it hasn't failed open.


I'll look into that. Can these be used as a "drop-in" replacement for
the ballast in the existing circuit? Then I just take the starers out
and leave their sockets empty?

You'd have to bypass the starters, I'm not sure how common electronic
ballasts are where the line voltage is 240v, here with 120v we need an
autotransformer ballast to step up the voltage for anything more than about
a 2' tube, so the electronic ballast buys a fair amount of efficiency. Over
there where a simple choke reactor can be used it's already quite efficient.

As someone else suggested, I would try the proper starters, if that doesn't
work then try swapping the ballast from a known good fixture.

 

[jfrog]

I have a light fitting that takes two tubes wired in series in what I
believe is the standard configuration. I've replaced both tubes twice
and replaced both starters with ones taken from fluorescent fittings
that work. I've also checked the ballast to make sure it hasn't failed
open (ohmmeter with the power off: 50 ohms) but I understand ballasts
rarely fail. I've gone around it with a voltmeter and an ohmmeter
checking for any other open circuits and all the wiring seems good.
(This is in the UK, so 240VAC 50Hz.)

The only difference is that the original tubes that worked were labelled
"18W/41" and the replacements (available near my house) are "18W/35".
They have the same length and diameter.

Any suggestions?

Thanks,
Adam

The difference between the 18W/41 and the 18W/35 is the former is cool
white and the latter is warm white.

What is the nature of your problem?

 

[H. R. Bob Hofmann]

I have a light fitting that takes two tubes wired in series in what I
believe is the standard configuration. I've replaced both tubes twice
and replaced both starters with ones taken from fluorescent fittings
that work. I've also checked the ballast to make sure it hasn't failed
open (ohmmeter with the power off: 50 ohms) but I understand ballasts
rarely fail. I've gone around it with a voltmeter and an ohmmeter
checking for any other open circuits and all the wiring seems good.
(This is in the UK, so 240VAC 50Hz.)

The only difference is that the original tubes that worked were labelled
"18W/41" and the replacements (available near my house) are "18W/35".
They have the same length and diameter.

Any suggestions?

Thanks,
Adam

I'm puzzled, but I'm from the other side of the Atlantic where we have
120V 60Hz input to most lights, other than commercial 207 V, 1-phase
of 3-phase fixtures.

If the lights are is series, why would there be 2 starters? Our
ballasts (magnetic) usually have a couple of wires feeding one end of
each of the tubes, and separate wires feeding the other ends of each
of the tubes, and no starters.

Interesting!

H. R.(Bob) Hofmann

 

[JM]

quoting:

There is no light _at_ _all_, although power is present in the fitting
(about 230V measured across the main terminals with the tubes in, and
on the appropriate contacts with the tubes out).

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.

 

[Victor Roberts]

I'm puzzled, but I'm from the other side of the Atlantic where we have
120V 60Hz input to most lights, other than commercial 207 V, 1-phase
of 3-phase fixtures.

If the lights are is series, why would there be 2 starters? Our
ballasts (magnetic) usually have a couple of wires feeding one end of
each of the tubes, and separate wires feeding the other ends of each
of the tubes, and no starters.

Interesting!

H. R.(Bob) Hofmann

Well, we also use starters here in the Colonies on our meager 120 Volt
power systems but generally only for fluorescent lamps with a length
of 2 feet or less. The operating voltage of longer lamps precludes
their operation with a simple series inductor from a 120 Volt power
source.

The system you describe, with "a couple of wires feeding one end of
each of the tubes" is known here as Rapid Start and provides superior
lamp life compared to systems using starters, known here as Switch
Start or Pre-Heat Start, and can be used with longer length, higher
voltage lamps.

 

[Steve Nosko]

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).

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

 

[Sam Goldwasser]

Rapid and trigger start use a HV low current winding on the ballast.

--- sam | Sci.Electronics.Repair FAQ Home Page: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
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| Mirror Site Info: http://www.repairfaq.org/REPAIR/F_mirror.html

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.

 

[pedrodeswift]

Good point, sorry!

There is no light _at_ _all_, although power is present in the fitting
(about 230V measured across the main terminals with the tubes in, and
on the appropriate contacts with the tubes out).

When you check with a multimeter the probes can make contact with the
metal connectors but that is not to say that the same contacts will
touch the tube pins when you put the tubes in (also applies to the
starters). In a single tube fitting if you rotate the tube slightly
you can sometimes get a connection but with 2 tubes the possible
combinations preclude this. All it takes is one pin to not connect and
you get no action at all. I would take the fitting down and check
continuity to the starter contacts with the tubes in. If no problem is
found then you should try to confirm that the starter contacts connect
to a starter to do this you may have to make a dummy starter. A
importer recently mentioned that he is having problems with starter
sockets and is changing the contact material.

I had these series lights and finally converted the fittings by
throwing away the series ballasts and fitting each light with 2 new
ballasts (one for each tube) with the added benefit that could then
use instant electronic starters. I have seen tenders where one tube
one ballast is specified and I know why.

 

[Steve Nosko]

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?

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