newbie with questions on retrofitting old stage lights

Hey all, I've got a sort of interesting problem on my hands... I'm the head A/V guy on campus at an emergency response training organization. I'm actually the only guy in the department, makes things interesting... Anyway, I know next to nothing about stage lighting. The campus we got about five years ago came with a large multipurpose gym with a stage, light, and sound setup that was probably very nice about 10 years ago. We haven't really had to use the stage for anything other than large promotions and graduations (which require very basic lighting), and I've been able to "make things work." During a large homeschooling conference last year a children's drama group came and did a performance for one of the sessions. Thankfully one of the guys that came in to help with the sound and lights did the lighting for it. I realized then that I needed to pay a lot more attention to maintaining the lighting system, and I realized that I needed to do it now when I found out last week that the same drama group was doing another performance soon.

Really I've got two problems. One, I know almost nothing about stage lighting, only what I've picked up just messing around with what we have and what I've read on this forum. Two, the lamp sockets or holders are burning out (carbon buildup, arc damage), and I'm not sure whether I should look for straight-across replacements, or look into retrofitting them to take a newer, more efficient bulb. They currently use a 1000 watt FEL, but from what I gather the FEL is an old, inefficient lamp design and I could probably get better performance from a newer bulb. Most of my fixtures are old Kliegl Brothers ellipsoidals (I'm not too sure on the ellipsoidal part, they have reflectors built into the fixture itself). I also have a few Berkley Colortran 40 degree ellipsoidals that have the same type of lamp socket.

I also have another style fixture, not sure what make it is (no markings). It's a shorter throw fixture than the Kliegl Brothers units, but it has a similar bulb/reflector configuration. It uses an EGM style bulb, they go in with a "push and turn to lock" action. The spring loaded contact on the bottom of the light bulb socket on a lot of them is also corroding and showing arc damage. Can I get away with cleaning those and using a heat-resistant deoxidant, or should I look at replacing/retrofitting them as well (also, what's a good deoxidant for the application?)?

I'm sorry if I'm asking things that have been answered in previous posts... I just don't know the lingo well enough yet to take answers that were given to other questions and apply it to my own challenge. Thanks in advance for the help!


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take and post a photo of the fixture in question.

In having read past posts - good for you, it would seem that you already know much of the answers or at least often my opinions. Just be sure to have that person who seems to know what he is doing at very least there with you when you service the equipment. Certain techniques and things you would not know better about could end up becoming very dangerous. Otherwise a repuitable service center might be willing to fix one fixture for you while you watch and get trained in fixing the rest.

Unfortunately telling who knows what they are doing in teaching you, or in one random fixture having all the problems you will see is a hard question to answer. Hedge your bet in trying to find some old man who is familior with the Kliegl lights in having used them. They are much different than a ETC fixture.

Given the push down and turn socket description, much less lamp given, it is a medium pre-focus lamp base. P-28s.

Very easy to clean. Brass wire wheel with Dremmel tool, and if the center of the base is arched you will have to do a little more to re-surface it. Than coat the exposed surface. Be mindful of your lamps also in that if they while in P-28s, it's more stable, still if damaged it's going to re-damage your freshly cleaned lamp base. Clean the button with an abrasive fiber grinder wheel. MIght also be possible to un-screw the center button on the lamp base and use the above fiber grinder wheel to hone and smooth the edge. Otherwise silicone based fine abrasive fiber wheels on the dremmel will be necessary to surface it.

By description, it sounds like your lights are a lot older than just 10 years old. Especially those with the EGM lamps. These fixtures are probably at least 30 years old.

Still once they function properly, there is nothing wrong with continuing to use them, and the EGM is a darned good lamp. The rest of your FEL lamps, yea change them. While your fixtures are probably rated for a 1Kw load, it's an in inefficient lamp.

Depending upon how bad the lamp bases are, all are cheap enough to replace instead of clean. A new lamp base runs about as much as a new lamp. Certainly much easier to install new lamp base than fix it when in doubt.

Hope it helps, use caution and learn from what you have while taking it apart. Try not to force your bolts either. The longer the gear has been un-cared for, the more chance screws will be rusted in place.


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Berkeley Colortran? That was way more than 10 years ago. Here is the short Colortran story, Berkley-bought out by Lee-bought out by Leviton(most records disappeared into the dark abyss of filing systems during this takeover)-current


As far as the choice of FEL vs FLK or other similar lamps (called light bulbs by laymen), I defer to ship. However, from reading your post, I got the impression that you wanted to replace the sockets (thing that holds and provides power to the lamp) with a different type of socket. I counsel strongly against that. Replacing them with the same or equivilant socket is all well and good, but when you change over to a different lamp base type (like the medium pre-focus of your EGM lamps instead of the bipin (is that what it's called?) base of the FEL, you screw up the optics of the lighting instrument. Bascially, by changing the socket, you change the position of the lamp filament within the reflector, and it is the precise positoining of that filimanet which makes and ellipsoidal so controlable.

However, sticking with the same socket type shouldn't be a problem at all. In fact, if you're trying to find replacement lamps for the FEL, almost all, if not every single one of them, will fit the same base.

Also, as you're an educational institution and on (I assume) a tight buget, I'd go with phasing out the FELs as the die, instead of replacing them all at once and throwing away the rest of their perfectly good lamp life.


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Premium Member
No worries in challenging me, we are in complete agreement in all ways. Nor would I abuse anyone calling a lamp a light bulb. Heck, I'm even trying to put into my lingo the "luminary" term as more "PC" these days than fixture. The terms as they are as long as understood what you are talking about is less important than understanding the intent unless my own intent is to play with you as also necessary. Had a person asking for a Mac 2K replacement lamp today. He asked for something like a HMI 200. Were it a normal tech person I might find fun in educating them so they do know what they are asking for, this was someone from the repair department in also helping (below) and he is more prone to fixing a sound cousule than re-lamping and needing to call from a truss to a stage hand what specific lamp he needs. I helped him without hassle. This once I understood I did not have to figure out if I still had any 200w arc source lamps in stock given he also said what type of fixture it was for.

Didn't get the concept of converting say a radial 360 series or similar fixture to medium bi-post G-9.5 or what people call the TP-22 series of lamp base from the question. Good that you are also lending your thoughts as if the intent, that's something I missed. This is not a ask the "Ship" type of forum though my long posts might intimidate otherwise at times as not intended. My intent as with anyone else's is to be of help. Though in my case being thorough with details in tech is thought to be of both use and necessity. Someone suing me because I provided brief advice is more a factor to me than to anyone else I hope is respected given I know better and in commenting and offering advice, I have to try to cover all bases to the extent possible without physically instructing. Thus long posts.

Yep, I agree in not attempting to swap the P-28s base with the G-9.5. It can be done in a similar way to how I did the 10K Fresnel re-lamping to 2Kw upgrade by way of jacking up the lamp base by 5", but that cited upgrade was also very difficult to do technically. Certainly not worth it given the optics of a incandescent series of Leko.

That incandescent to halogen lamp upgrade while archaic in also being jacked up in length is still a really reliable and cost effective lamp - unlike the FEL.

One slight difference between me on doing a FEL upgrade would be very much dependant upon what the FEL outfitted fixtures look like in comparison to the upgraded fixtures for lamp. While I would not just do a total swap, I might pull some lamps in having some used FEL replacements for those less important fixtures, but still also have what I needed for the important lights. Lots of ways to cost effectively merge in new technology. Would like to hear more about your own system for this.

If of any help in being archaic, I at the moment find myself in the Leko prep area. Somehow in the last few weeks I got caught up for the most part in stuff that really needs to get fixed immediately, and the prep area is experiencing a major shortfall in labor needed to get shows out the door. What the heck, I'm a company man, I'll give it a shot in doing mindless labor and even loading trucks for a week.

This given I'm paid to do stuff I need to concentrate on and think about, much less between desk and work table, my back and feet by now are killing me by the end of the day.
Ok, let me see if I got this straight...

I can replace the FEL with a reasonably equivilant lamp (the GLE, HPR, or Phillips #6981P, if I read past posts correctly) without having to change to a different type of socket. The socket that I currently have (that takes the FEL) is called a TP-22, G-9.5, or medium bi-pin socket, and if I find a replacement socket with one of those descriptions then I can be reasonably sure that it will work in my fixtures. The other fixtures that take the EGM lamp (that use a p-28s base) will be fine if I just clean off, resurface as needed, and protect the damaged contacts. Have I gotten it so far?

Working on getting pictures posted to some webspace, hopefully should have that by the end of the day.


Any fool can make things bigger, more complex, and more violent. It takes a touch of genius--and a lot of courage--to move in the opposite direction.

- Albert Einstein


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The TP-22 is a Medium Bi-Pin or G-9.5 based lamp socket. Just as you can change wattage or from say clear to inside frost in a medium screw E-26 based household light socket, you can change wattages and types of lamp in a Leko as long as it's using the same style of lamp base. In this case all do as it's a very standardized lamp base type.

The G-9.5 is a more accurate description in meaning "G" is bi-pin and having two equal sized pins, and 9.5 meaning 9.5mm on center. There are other types of 9.5mm on center bi-pin lamps on the market but all will have a second even at times a third letter in the base type description. Such as GX or GZZ. The GZ-9.5 for instance in 600w is a standard ray-light lamp by the name of DYS/DYV/BHC. Many people on the forum use this type of lamp with it's similar but different lamp base type. Such letters designate that while the pins have the same spacing, there is other details to the pin and base design such as one oval one round, different size pins or other details.

This is getting a bit complex but as long as you have a lamp saying that it's a G-9.5 or in falling less in use the description of medium bi-pin it should be what will be necessary to fit into the lamp socket.

After this, in confirming a lamp will work in the fixture, a question of the length of the lamp comes up. All of these above more modern Leko lamps have a "LCL" or lamp center length of 2.3/8". This is the specified distance between a set point on or near the lamp base and the center of the filament.

Dependant upon what style of lamp base is used, this set point can cange between lamp types but within a specific type of lamp base it is always the same specified measurement point.

For instance with your EGM lamp, it has a distance of 3.1/2" from the locking fins of the "medium pre-focus" P-28s lamp socket and the center of the filament.
("P" for single socket with locking alignment fins and no screw base to it, "28mm" in dia, and "s" for single center contact.)
All other lamps of the type in that wattage still made: DNT/FMD, EGF, & EGG will also thus work in your older Leko.

But there is also lamps with a P-28s lamp base such as you might find on a standard Fresnel in this 750w range, while they will fit into the lamp base, the length from filament to lamp base fins is much different. Instead it's only 2.3/16". This older style of Leko using the EGG is a halogen lamp that was made to directly upgrade some narrow dia. but long incandescent lamps which because of cooling needed to be larger so as not to reduce reflector cut out hole, yet still required a certain amount of cubic area within the lamp for proper cooling. The Fresnel on the other hand has lots of room for a fatter more squat incandescent lamp thus it could be much shorter. In many ways, the EGG lamp is symilar to those lamps designed for a Fresnel - just much longer instead of more squat. That distance than is the primary difference between the two types.

There are lots of other minor and major differences that go into lamp design, but in judging one lamp to another, beyond ensuring voltage and wattage are the same, one needs to ensure both lamp base type and LCL.

My opinions for the best Leko lamps are:
575w/115v = Osram HPR for high output or Phillips GLA for long life.
750w/115v = Philips #6981P (or #6982P - Philips is having some lamp coding problems for the same lamp) or the GE/Thorn GLE/HX-705 lamp for long life.

After that, there is also the HX-400 & 401 series of lamp for times you don't need as much light and dimming will otherwise cause amber shift problems.

All use the same lamp base as similar to the EHD, FLK/HX-600, EHG, FEL system of Leko lamps in the past.

On the radial style of Leko, there is the DNT which is between 200 & 500 hours in life, 3,050°K which is hot for a incandescent lamp, and 17,000 Lumens in light output. Or the EGF which is more or less a high output direct halogen replacement for it at 500 hours life, 3,200°K in color temperature and between 20,000 and 20,400 Lumens. Or the EGG I think most efficient at 2,000 hours life, 2,900°K to 3,000°K, and between 15,000 to 15,750 Lumens of light.

Given the 2,000 hour lamp, it's much more worth less output and color temperature, though at 500 hours, the EGF is not that bad, and given it's output and color temperature that's in the range of a more modern Leko lamp, such high output lamps might be worth the extra cost during their life so as to better match up with more modern Lekos and not look as dim in comparision. The EGF thus should be considered as a good viable option.

In 500w, the EGC high output and EGE long life lamps are the best two options otherwise. Some companies stil do make the DNS/FMC lamps in both incandescent and halogen versions of them, along with the DEB incandescent lamp that's the long life version. Such DNS/DEB lamps are very obsolete other than special purpose looks.


if it is carbon build up that you have you should use sodium hydroxide a 2 molar solution. my chemistry teacher suggested this and it works wonders.


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if it is carbon build up that you have you should use sodium hydroxide a 2 molar solution. my chemistry teacher suggested this and it works wonders.

While its okay to bring back necro posts if you are in similar situation or have some suggestion that could be extremely helpful, a wire brush works just as well, and generally its not the lamp itself and rather the ceramic socket that's the issue.

Also say hi in the newbie section its always nice to hear about students from SD getting into control booth. and remember search function is your friend since this topic I know from the time i've been here has been covered at least 4 times.

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