One light in fluorescent lamp randomly starts

Check connections and/or new tubes new ballasts.

Like Tom said also change the tubes over and see if its the one tube U/s

Normal old style start circuit where a 'starter' is not used. This circuit is found on desk/counter fluorescent lights where you pushed a button to light the tube, after holding the button for a second or two. Button switch is momentary on.

The bulbs are independent of each other (even though the start windings are shorted together for starting) - each has a ballast. I would expect that the tube that doesn't light has a bad ballast. Did you exchange the bulbs to see if the good one lights in the other position? It may also be that the tube connector pins are bent or a broken connection. Use an ohm-meter to check continuity with only one bulb installed at a time.

This light was just after WWII is my guess, and starters were not always used.

If you need a 15watt ballast they are around $10US - you want the two-wire version. We use these in jukeboxes and arcade games.

John :-#)#

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fixing. It weighs a ton, has been passed down from my father-in-law, and i t just retro-cool. According to him it's always worked, except the F15-T8 b ulbs are possibly original and very worn out, and only one bulb ever lights . I've been told this has always been a problem, and holding the start butt on for a long time will sometimes get both to start. I've never been succes sful but I don't like this and want to fix it.

awn in Paint!):

both lamps seems odd to me, a little like directly paralleling LEDs or neo n bulbs after the limit resistor. If I disconnect one bulb, the remaining a lways starts. I doubt this design would ever work very well....would it?

d momentarily shorting the two pins at opposite ends of each lamp, they eac h start right up. My plan is to modify it with a DPDT relay with 120VAC coi l so the start button drives the coil, and each lamp has it's own set of re lay contacts. I'm sure this will work, but.....WTF with the original design ? Is this normal? I doubt it's even been modified, and see no good way to fix it without adding a relay or a multipole start switch.

hing this old.

The circuit is a right bodge. The 2 tubes are connected in parallel, the li t one will be taking around twice its rated run current.

NT

I should clarify a few things.

-I already purchased new bulbs. The old ones worked but were very dim.

-The ballasts each measure about 30 ohms. I have not yet put an inductance meter on them but my guess is they are good.

-I connected the bulbs using jumper wires to eliminate bad connections in t he sockets. No change.

-If I install only one bulb with everything wired as it originally was, tha t one always starts. If I remove it and install the other bulb in the other bulb socket pair, that one also always starts. With both in circuit, I've never seen them both start, only one does.

-With both bulbs in circuit one specific bulb tends to start, but randomly the other does instead.

-If I separate out each bulb-ballast circuit so they look like completely i ndependent fixtures and start each manually by temporarily shorting the one bulb pin at each end, each starts and runs no problem. So that's why I bel ieve both ballasts are good.

The part of the original circuit I'm having trouble dealing with is how the bulbs are permanently connected at the same end as the ballast connection. It seems one bulb could steal the start pulse from both ballasts, hence th e reason for the issue. But then again this was designed this way and suppo sedly would work?

I have a DPDT relay on the way to isolate each starting switch and that wil l fix it, but did these desk lamps ever intend to work correctly? Seems odd .

I suspect you have Rapid Start bulbs that are self starting. What is the code number of the bulbs you used?

A quick ballast test is to power up the fixture then read the ballast side against the other side of the line - should be around 130VAC. If it show 115 (or whatever your AC source is) then the ballast is bad.

Try grounding the metal frame of the fixture. Or if grounded (someone would have added that, wouldn't have been there originally), remove the ground

True.

The bulbs are only connected to the non-ballast line side when the button is pressed. Otherwise the interconnections can't conduct current as they are on the same side of the line for each bulb.

Why not use a DPDT push button switch? While I don't think it will change anything it can be wired to isolate the two bulbs from each other more easily than fitting a relay in there.

It is odd, I agree, that both bulbs won't light if everything is as described. They should. You do press and hold the button until the ends of the tubes glow for a second, right?

John :-#)#

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It's item# 147940 from Lowe's, and the specs say they are not rapid start.

nce meter on them but my guess is they are good.

in the sockets. No change.

that one always starts. If I remove it and install the other bulb in the o ther bulb socket pair, that one also always starts. With both in circuit, I 've never seen them both start, only one does.

Interesting. It does have the original cord but I've considered putting a g rounded cord on there because I started wondering about the safety of this thing should something internally touch the enclosure. For what it's worth, is does the same even with the innards laying out on a table.

mly the other does instead.

ly independent fixtures and start each manually by temporarily shorting the one bulb pin at each end, each starts and runs no problem. So that's why I believe both ballasts are good.

the bulbs are permanently connected at the same end as the ballast connect ion. It seems one bulb could steal the start pulse from both ballasts, henc e the reason for the issue. But then again this was designed this way and s upposedly would work?

I was most concerned about the ballast side of the bulbs where they essenti ally connect together through the heater/filament even when start isn't pre ssed. That seems like not such a good design and maybe why the problem is o ccurring.

will fix it, but did these desk lamps ever intend to work correctly? Seems odd..

That's what I first looked at, but the relay was much cheaper and most impo rtantly, keeps the outward appearance the same. There's also plenty of room inside this thing.

Oh yeah. I pressed and held it, and both ends of both bulbs begin glowing w hite. When I release it, one lights, and the other has this very dim flicke r that decays within a few seconds. The interesting thing is one end of one bulb randomly flickers while holding start. Now whether that's the one tha t doesn't start, I didn't think to observe until now.

This may sound stupid but did you check you line voltage where you are doing this testing?

.

he

art.

tance meter on them but my guess is they are good.

it

s in the sockets. No change.

s, that one always starts. If I remove it and install the other bulb in the other bulb socket pair, that one also always starts. With both in circuit, I've never seen them both start, only one does.

e

a grounded cord on there because I started wondering about the safety of t his thing should something internally touch the enclosure. For what it's wo rth, is does the same even with the innards laying out on a table.

domly the other does instead.

tely independent fixtures and start each manually by temporarily shorting t he one bulb pin at each end, each starts and runs no problem. So that's why I believe both ballasts are good.

ow the bulbs are permanently connected at the same end as the ballast conne ction. It seems one bulb could steal the start pulse from both ballasts, he nce the reason for the issue. But then again this was designed this way and supposedly would work?

t

entially connect together through the heater/filament even when start isn't pressed. That seems like not such a good design and maybe why the problem is occurring.

at will fix it, but did these desk lamps ever intend to work correctly? See ms odd..

er

importantly, keeps the outward appearance the same. There's also plenty of room inside this thing.

s

ng white. When I release it, one lights, and the other has this very dim fl icker that decays within a few seconds. The interesting thing is one end of one bulb randomly flickers while holding start. Now whether that's the one that doesn't start, I didn't think to observe until now.

It's near 120VAC as it should be. It's in my house plugged into a regular o utlet.

I think your assessment is correct, that the two lamps that have the ballast side of their filaments connected together may be the problem. It is odd as I'm sure thousands of these lights were made and would have worked correctly with the wiring as you showed.

Let's see what happens once you get the relay wired in.

Randomly flickering on one bulb when the start is pressed suggests a problem with a connection to the bulb. I'd look into that more.

More info on fluorescent lamps that you will ever need to know, but they talk about lag time which may have a bearing...

John :-#)#

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. e

t.

tance meter on them but my guess is they are good.

t

s in the sockets. No change.

s, that one always starts. If I remove it and install the other bulb in the other bulb socket pair, that one also always starts. With both in circuit, I've never seen them both start, only one does.

grounded cord on there because I started wondering about the safety of thi s thing should something internally touch the enclosure. For what it's wort h, is does the same even with the innards laying out on a table.

The electrical properties of fluorescent tubes plus their method of startin g makes what you see happening inevitable. The circuit is a complete bodge. The solution is to separate the tubes at the ballast end, requiring a 2 po le push switch.

domly the other does instead.

tely independent fixtures and start each manually by temporarily shorting t he one bulb pin at each end, each starts and runs no problem. So that's why I believe both ballasts are good.

ow the bulbs are permanently connected at the same end as the ballast conne ction. It seems one bulb could steal the start pulse from both ballasts, he nce the reason for the issue. But then again this was designed this way and supposedly would work?

tially connect together through the heater/filament even when start isn't p ressed. That seems like not such a good design and maybe why the problem is occurring.

at will fix it, but did these desk lamps ever intend to work correctly? See ms odd..

r

portantly, keeps the outward appearance the same. There's also plenty of ro om inside this thing.

white. When I release it, one lights, and the other has this very dim flic ker that decays within a few seconds. The interesting thing is one end of o ne bulb randomly flickers while holding start. Now whether that's the one t hat doesn't start, I didn't think to observe until now.

...

This circuit is indeed rather unreliable, one lamp will always fail to start. The reason is that the filaments have a rather low resistance and as soon as one discharge is ionized, it will steal the remaining start pulse from the other lamp through the filament resistance. It will also overload the lamp that works because additional current will be driven into it through the other lamp's filament.

There are at least 3 ways to fix this (roughly in order of usefulness):

1. Change the SPST start button to a DPST one, use one pole per lamp.

1. Keep the SPST button but add a DPST relay to start the lamps via the relay contacts and use the button to energize the relay coil.

2. Put a center-tapped inductor between the lamps as shown here:

This will present a low impedance to the preheat current (inductor has opposite-phase windings, being essentially shorted) but a much higher impedance to the ignition pulse (inductor has in-phase windings, being essentially open to high frequency components from a pulse). The 1kV varistor is only there to protect the switch contacts from arcing.

Been reading this thread.

Would one of these fit? If so, install one, pick the lamps you want - and be done with it. All the nostalgia, but fully functional and less energy used.

Peter Wieck Melrose Park, PA

Why do some people rip long lived original stuff out of historic items, fit junk instead, and pay for doing so? Senseless.

NT

Long-lived? Sure, the ballast may be long-lived - it is essentially a step-up only device, but the consumables that go with it lasted a fraction of what a modern lamp will last, used far more power and give far less light per watt.

So, about 12,000 hours (at best) vs. about 32,000 hours (on average) of longevity. CRI of 69 vs. up to 96.

34 watts (at best) to as little as 25 watts for equivalent output. Much better aging.

Seems like a pretty simple choice to me. I would prefer to keep my money for other things than wasting it needlessly on power.

Peter Wieck Melrose Park, PA

fit junk instead, and pay for doing so? Senseless.

p-up only device, but the consumables that go with it lasted a fraction of what a modern lamp will last, used far more power and give far less light p er watt.

ongevity.

for other things than wasting it needlessly on power.

That seems confused. I was talking about the ballasts, which obviously do n ot need replacing. The tubes you refer to are hardly likely to be original, and even if they are replacing them won't save any power or money. All the OP needs is a 2 pole switch or relay.

NT

not need replacing. The tubes you refer to are hardly likely to be origina l, and even if they are replacing them won't save any power or money. All t he OP needs is a 2 pole switch or relay.

It is the ballasts that drive the consumables. Magnetic ballasts of that vi ntage cannot handle T8 or T5 lamps, some cannot even handle high-efficiency T12 lamps. They also require manual-start switch systems which further deg rades the lamps. They also consume considerable power in their own right.

A "smart" electronic ballast will adapt to various lamp options, consumes 3

0% less power, and will very nearly triple the longevity of the lamps and h alve the overall power consumption. As well as being adaptable to input pow er from 100 - 240 VAC.

The analogy I would use is that I am not required to use single-weight non- detergent oil, paper oil filters (if any at all) and non-resistor plugs in a vintage automobile. Nor am I required to use gutta-percha gaskets or leat her belts - that is if I actually wish to drive it.

Peter Wieck Melrose Park, PA

do not need replacing. The tubes you refer to are hardly likely to be origi nal, and even if they are replacing them won't save any power or money. All the OP needs is a 2 pole switch or relay.

vintage cannot handle T8 or T5 lamps, some cannot even handle high-efficien cy T12 lamps. They also require manual-start switch systems which further d egrades the lamps. They also consume considerable power in their own right.

30% less power, and will very nearly triple the longevity of the lamps and halve the overall power consumption. As well as being adaptable to input p ower from 100 - 240 VAC.

n-detergent oil, paper oil filters (if any at all) and non-resistor plugs i n a vintage automobile. Nor am I required to use gutta-percha gaskets or le ather belts - that is if I actually wish to drive it.

US fluorescent lighting is different to UK in many ways. All our historic s witchstart ballasts work fine with T12, T8 and a lot of LED tubes.

NT

switchstart ballasts work fine with T12, T8 and a lot of LED tubes.

That would explain a lot of your attitude. But, your electrical power is, o n average, 50% more costly than power in the US - one would think that ener gy efficiency would would be of greater concern to you than it seems to be. We operate a 464 square meter center-hall colonial built in 1890 for US$23

9/month (180 GBP). And we heat in the winter and cool in the summer. This i ncludes heat, hot water, electricity, cooking, drying, and municipal water and sewer. Yes, we use a clothes line in the summer. But energy is dirt-che ap in the US relative to the rest of the world - not to suggest we waste it , but the only incandescent lamps we own are in the chandeliers. They too, are slowly giving way to LEDs.

Peter Wieck Melrose Park, PA