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Dim florescent lamp

W

warren upchurch

Jan 1, 1970
0
I have run across an unusual situation a few times in the last few years.
Usually in a plastic sign, I will see 3 out of 4 lamps lit and one doesn't
appear lit. This is on a 4 lamp series start ballast. When you remove the
lamp that is not lit the others go out, and replacing the lamp results in
all 4 lit. Any ideas as to what causes this?
Thanks
Warren
 
A

AC/DCdude17

Jan 1, 1970
0
X-No-Archive: Yes

warren said:
I have run across an unusual situation a few times in the last few years.
Usually in a plastic sign, I will see 3 out of 4 lamps lit and one doesn't
appear lit. This is on a 4 lamp series start ballast. When you remove the
lamp that is not lit the others go out, and replacing the lamp results in
all 4 lit. Any ideas as to what causes this?
Thanks
Warren

Sign ballast may have a weird wiring, but generally, many ballasts are
series wired. Did you mean one lamp is out, but one of the other lamps
is lit dimly? The light output is quite low in this situation and it
can get confusing in the daylight.

Basically, if part of series circuit fails, everything in that circuit
fails. If it's a four lamper, it is most likely a pair of two series
circuit.

You should replace all the lamps because lamps are cheap, service calls
are not.
 
A

Andrew Gabriel

Jan 1, 1970
0
I have run across an unusual situation a few times in the last few years.
Usually in a plastic sign, I will see 3 out of 4 lamps lit and one doesn't
appear lit. This is on a 4 lamp series start ballast. When you remove the
lamp that is not lit the others go out, and replacing the lamp results in
all 4 lit. Any ideas as to what causes this?

Perhaps it's lost its mercury somewhere?
In that case you typically get a dim and different
coloured glow from the gas in the tube and probably
no phosphor excitement.
 
C

Clive Mitchell

Jan 1, 1970
0
Andrew Gabriel said:
Perhaps it's lost its mercury somewhere? In that case you typically get
a dim and different coloured glow from the gas in the tube and probably
no phosphor excitement.

If it's similar to the series circuits sometimes used to run two lamps
on a single ballast in the UK, then a dead lamp will still pass current
through it's heaters if the starter welds.
 
J

JM

Jan 1, 1970
0
quoting:
Sign ballast may have a weird wiring, but generally, many ballasts are
series wired. Did you mean one lamp is out, but one of the other lamps
is lit dimly? The light output is quite low in this situation and it
can get confusing in the daylight.

Basically, if part of series circuit fails, everything in that circuit
fails. If it's a four lamper, it is most likely a pair of two series
circuit.

You should replace all the lamps because lamps are cheap, service calls
are not.


I've seen this happen in one the signs I relamped about 5 years ago. The
sign had two ballasts and 8 lamps. F60T12HO . On one half of the sign, one
lamp did not light. The other three in that half litghted properly, but it
didn't matter if the non-lighting lamp was in the holders or not. I
attributed it to a short somewhere that just jumpered that lamp out of the
circuit.
 
W

warren upchurch

Jan 1, 1970
0
X-No-Archive: Yes



Sign ballast may have a weird wiring, but generally, many ballasts are
series wired. Did you mean one lamp is out, but one of the other
lamps is lit dimly? The light output is quite low in this situation
and it can get confusing in the daylight.

Basically, if part of series circuit fails, everything in that circuit
fails. If it's a four lamper, it is most likely a pair of two series
circuit.

You should replace all the lamps because lamps are cheap, service
calls are not.

What I'm talking about specificaly are two signs that were relamped
about a year ago (by me) as part of an ongoing maintainance program.
During this years inspection the lamps in question were not visibly lit,
while the others on the same ballast were. When the offending lamp was
replaced, it as well as the others lit at full intensity.
I have noticed this a few times over the years on other series ballasts,
but never thought to put the question to the group.
I hope this clarifies the question, sorry for any confusion caused by my
poor description of the situation.
Warren
 
N

Nick Hull

Jan 1, 1970
0
warren upchurch said:
I have run across an unusual situation a few times in the last few years.
Usually in a plastic sign, I will see 3 out of 4 lamps lit and one doesn't
appear lit. This is on a 4 lamp series start ballast. When you remove the
lamp that is not lit the others go out, and replacing the lamp results in
all 4 lit. Any ideas as to what causes this?
Thanks
Warren

It's possible that the lamp is operating and just producing little
light. I saw this in MA at an indoor range off the grid, the lamps
froze often and were subject to shock from gunshots. The result was
that a lot of the phosphor flaked off inside the tube and piled up in
the bottom. Probably produced a lot of UV but the phosphor was getting
little since it either wasn't there or was piled too deep.
 
V

Victor Roberts

Jan 1, 1970
0
If it's similar to the series circuits sometimes used to run two lamps
on a single ballast in the UK, then a dead lamp will still pass current
through it's heaters if the starter welds.

Interesting. I have never seen series-connected "switch start" or
"pre-heat", as we call them in the colonies, lamps in the US. This
question shows the importance of stating the line voltage and country
or region of the world when posting a lamp/ballast related question.
 
A

Andrew Gabriel

Jan 1, 1970
0
Interesting. I have never seen series-connected "switch start" or
"pre-heat", as we call them in the colonies, lamps in the US. This
question shows the importance of stating the line voltage and country
or region of the world when posting a lamp/ballast related question.

This is very common with 2' T8 tubes (18W for us, maybe 16W for you?)
in modular ceiling luminares in Europe. It's not used for longer tubes.
 
C

Clive Mitchell

Jan 1, 1970
0
Andrew Gabriel said:
This is very common with 2' T8 tubes (18W for us, maybe 16W for you?)
in modular ceiling luminares in Europe. It's not used for longer tubes.

It's also a grind because this application needs 110V starters and when
a tube fails it can cause very unusual disco effects when it's trying to
restrike.
 
C

Clive Mitchell

Jan 1, 1970
0
Nick Hull said:
It's possible that the lamp is operating and just producing little
light. I saw this in MA at an indoor range off the grid, the lamps
froze often and were subject to shock from gunshots. The result was
that a lot of the phosphor flaked off inside the tube and piled up in
the bottom. Probably produced a lot of UV but the phosphor was getting
little since it either wasn't there or was piled too deep.

Even mercury absorption or polarisation could give this effect. The
dull purple glow of the argon on it's own would be hard to see outdoors.
 
J

JM

Jan 1, 1970
0
quoting:
This is very common with 2' T8 tubes (18W for us, maybe 16W for you?)
in modular ceiling luminares in Europe. It's not used for longer tubes.


17w, T8, electronic ballasts. We do have the 18w, it is sold as an
"appliance lamp". I see them in 2 foot under cabinet fixtures with a series
inductor and a starter.
 
T

TKM

Jan 1, 1970
0
warren upchurch said:
I have run across an unusual situation a few times in the last few years.
Usually in a plastic sign, I will see 3 out of 4 lamps lit and one doesn't
appear lit. This is on a 4 lamp series start ballast. When you remove the
lamp that is not lit the others go out, and replacing the lamp results in
all 4 lit. Any ideas as to what causes this?
Thanks
Warren

A key question is whether the lamps involved are T12/HO or slimline.

Terry McGowan
 
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