Rewiring a ballast. Help needed.

Excellent webpage about fluorescent lamp theory, and how to wire them. There are some ASCII type diagrams towards the bottom of the document. The diagrams shown, are very standard.

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Jerry G. ======

Thanks a lot! Sean.

If I understand all this correctly the switch has four connections. Is that correct? From your description is seems that this is a Preheat (switch start) circuit and you will not be able to replace the four-contact switch with a two-contact switch of any type. The switch provides the functions of both power switch and starter switch. (It must have three positions, even if one is momentary: Off, On, and Start.) You could use a standard power switch and then a glow bottle starter - if you can find one to match your lamp - but you would be better off replacing the ballast with something more modern that can be controlled with a simple series switch.

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I bet you press and hold the switch, then release it. During the press and hold the lamp is shorted out to preheat the filaments. You need the special switch. Ask at a hardware store, but make sure the guy knows what he is talking about.

Thanks for the reference. The diagrams help a lot. Sean.

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While it's hard for me to visualize without a drawing, it sounds somewhat like a switch start preheat ballast where you turn the switch on and hold it for a moment to preheat the cathodes. If that's the case then to bypass it you would need to install a starter in place of the starting contacts in the power switch.

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You can buy a glowbottle starter at any hardware store, usually under a dollar.

But it must match his lamp. While the Op did not give us lamp data, he indicated it was a 40-watt ballast. Therefore I am assuming the lamp is a 40-watt or 34-watt lamp (until I get better information.) If the OP lives in the US, I do not believe he can purchase a glow starter for 40-watt lamps since they will not operate from 120 volt power supplies. if the OP lives in a part of the work where the normal supply voltage is 220 to 240 volts, he should be able to find a glow starter.

I have found also that starters are quite non critical, and I've used a 20W starter in a pinch, though it likely wouldn't last as long.

I appreciate your desire to get this to work & the fun/challenge therein, but should it prove to be more f'ing around than it's worth, keep in mind you can buy a brand new 4' single tube starterless light for $10-15. They usually come "knocked down", so it would be a pretty easy task to fit the new ballast etc to the existing fixture/fish tank, should you not be able to use the entire new fixture itself.

Dan

Sean wrote:

Actually rapid start is much older than the 1970's, but you are correct about 40-watt preheat start lamps. The 1981 IES Handbook lists both 40-watt T12 and 90-watt T17 preheat start lamps. Thanks - I learned something new today.

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Perhaps it was 60's? I'm not sure really, but I do know that preheat start

The 90W T17 lamps are dinosaurs, I've never actually seen one up close but they were used in streetlighting some in the 50's. Another neat lamp I'd love to get my hands on are the GE PowerGroove PG17 series of VHO (1500mA) lamps that were somewhat common in the 70's. They use a rippled tube that allows a 9' arc length in an 8' tube and were available in 4' as well.

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Add a glow lamp starter to the circuit. That should work fine with the existing ballast. Otherwise you'll need a complete new ballast, and a complete new lamp is cheaper. In Canada you can get models with an electronic ballast quite cheap. Home Depot or Rona will have these - possibly on sale. They plug in, so you can plug it into a wall timer. Easy, cheap!

We need some input from Terry here, but we developed the 34-watt T12 energy saving lamp while I was working at GE Lighting in the mid-1970's. One problem with the lamp was that due to the lower lamp voltage the 34-watt lamp placed more voltage stress on the internal capacitor in rapid start ballasts. When the new 34-watt lamp was installed in fixtures with old rapid start ballasts, many of the capacitors, which were near end of life anyway, blew. So these ballasts must have been almost 20 years old by 1975- which means they were popular by the mid-1950s. By the mid-1970's the 40-watt rapid start lamp was nearing the end of its life due to the new 34-watt rapid start lamp.

Well, we had lots of Power Groove lamps at Nela Park along with its inventor - who I believe was Gene Lemmers - who also co-invented the rapid start ballast, I believe with John Aicher. Terry, can you help here? The Power Groove lamp was introduced by GE about 1956 and was a rapid start lamp, so the basic rapid start system must be older than that.

Those 34W lamps were (and are) awful, always dim and they flicker if it's even a bit chilly. I always thought it was so silly that with the regulations for efficiency of the lamps and ballasts the end result was that we had more efficient but dim lamps so you had to use more of them resulting in a net increase in ballast losses and overall power.

I didn't realize the PG's came out so long ago. HO and VHO have always been RS as far as I know, for some reason it took longer for RS to catch on for indoor use though, I'm not really sure why. You don't see many PG lamps anymore, I think only the 96" version is still in production. VHO in general is not real popular these days, I have a couple 4' VHO fixtures in my garage, they're very bright but not real efficient and the phosphor is hit so hard with UV that it degrades fairly rapidly. It'd probably work well using a modern trichromatic phosphor but as far as I know nobody makes those.

Someone else gave you a link to Don's lighting site. Look and the second diagram under preheat start. That being said, you need more information than you provided in your original note.

You will see from Don's diagram and perhaps your own experience, that each end of the lamp has two pins. You have told us in your original note that a certain wire goes to a certain end of the lamp, but NOT TO WHICH PIN, which is critical.

Based on what you wrote, I THINK that the starter would wired to the two wires that go respectively to the top left and top right contact of your switch. But this is ONLY correct if the wire currently connected to the top right hand contact of the switch is also connected to the pin on the right side of the lamp that does NOT also connect to the power line. I assume that the white lead from the ballast goes to the SAME lamp pin as the power line, so there are two wires connected to this AND ONLY THIS lamp pin.

If my assumptions about which wires go to which lamp pins are not correct, then the rest of my suggestions should be ignored.

If the above is correct, then the timer switch is wired between the two bottom contacts of the switch.

The information above is provided for educational purposes and you are responsible for understanding the hazards of working with electrical circuits and any damage to person or property that may result from experimenting with this lamp circuit.

Actually, they are my diagrams. :)

Huh? Unless I misunderstand your statement, it is irrelevant.

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I apologize for the error.

The OP has described 5 wires going to a 4-pin lamp - so (at least) one lamp pin must have two wires. One of those 5 wires goes directly to the power line. He must not connect the starter to the lamp pin that is connected to the power line. As you know, the starter is to be connected from one end of the lamp to the other, and connected to the side of each electrodes that is not connected to the ballast or power line per _your_ diagram :-)