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Author Topic: Replacing 750W E39 lamp with Dimmable LED  (Read 1010 times)

Erik Jerde

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Replacing 750W E39 lamp with Dimmable LED
« on: October 22, 2020, 09:35:56 pm »

I've got a few architectural church fixtures (from the 20's or 30's I believe) that take a rather large lamp https://www.bulborama.com/750-WATT-PS52-CLEAR-MOGUL-INDUSTRIAL-GRADE-LIGHT-BULB-p2534.html.  I've got a few to relamp and a lift rental is required so I'd like to swap them to LED.  It looks like there are standard replacements for these with "corn cob" LED array lamps.  750W is about 10K lumens.  It would be easy except I'd really like to preserve having these fixtures be dim-able.  Anyone tangled with this type of thing before?  I'm not opposed to re-working the fixtures.  They are probably 3 feet tall and this lamp is in the down position with another (not sure what kind) of lamp in an up position.  There really isn't room to add lots of electronics though I'd be fine putting electronics up in the attic space above the ceiling if necessary.

I'm not looking to get stage quality of dimming, no need to go barely on.  I'd just like a residential LED lamp level of dimming with no flicker.

Thoughts?
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Caleb Dueck

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Re: Replacing 750W E39 lamp with Dimmable LED
« Reply #1 on: October 23, 2020, 02:25:58 am »

I've got a few architectural church fixtures (from the 20's or 30's I believe) that take a rather large lamp https://www.bulborama.com/750-WATT-PS52-CLEAR-MOGUL-INDUSTRIAL-GRADE-LIGHT-BULB-p2534.html.  I've got a few to relamp and a lift rental is required so I'd like to swap them to LED.  It looks like there are standard replacements for these with "corn cob" LED array lamps.  750W is about 10K lumens.  It would be easy except I'd really like to preserve having these fixtures be dim-able.  Anyone tangled with this type of thing before?  I'm not opposed to re-working the fixtures.  They are probably 3 feet tall and this lamp is in the down position with another (not sure what kind) of lamp in an up position.  There really isn't room to add lots of electronics though I'd be fine putting electronics up in the attic space above the ceiling if necessary.

I'm not looking to get stage quality of dimming, no need to go barely on.  I'd just like a residential LED lamp level of dimming with no flicker.

Thoughts?

I've never run across those before, but it looks like a cool project!

Not much to add except - if you need to add external drivers to dim the diodes, eldoLED has a wide range that can be ordered with DMX control, 120V, and if you buy a special adapter from them, you can use their software to modify the dimming parameters.   
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Scott Hofmann

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Re: Replacing 750W E39 lamp with Dimmable LED
« Reply #2 on: October 23, 2020, 10:29:17 am »

This fixture sounds like the typical pendant type found in a lot of churches. See photo. Does it have a glass reflector for the PS52?
I just did a small church with 10 of these that used PS52 500watt lamps (not your 750 watt) and replaced them with GE 76043 15watt 3000K med.screw base with mogul to med.base adapters. Admittedly the bottom of the fixture was only about 16' above the floor but still the level of illumination was surprisingly adequate according to the church committee that reviewed it. Residential-quality dimming was required in this case as well. We kept the incandescent uplighting lamps in the top portion of the pendant to add some load to the Lightronics AR 1202 commercial dimmer cabinet.

In a school auditorium with a 28' ceiling and large can lights with no reflector and 500watt PS52's, we replaced them with GE 88810 32watt PAR38 40 degree LED lamps and achieved excellent brightness and theatre-quality dimming with an old Electro-Controls Quad dimmer rack.

In both cases, we did testing to be reasonably certain of the results but still had compatibility issues to overcome. In the above instances, access was not difficult so you have that problem to deal with.
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Scott Hofmann

Erik Jerde

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Re: Replacing 750W E39 lamp with Dimmable LED
« Reply #3 on: October 23, 2020, 01:30:34 pm »

This fixture sounds like the typical pendant type found in a lot of churches. See photo. Does it have a glass reflector for the PS52?
I just did a small church with 10 of these that used PS52 500watt lamps (not your 750 watt) and replaced them with GE 76043 15watt 3000K med.screw base with mogul to med.base adapters. Admittedly the bottom of the fixture was only about 16' above the floor but still the level of illumination was surprisingly adequate according to the church committee that reviewed it. Residential-quality dimming was required in this case as well. We kept the incandescent uplighting lamps in the top portion of the pendant to add some load to the Lightronics AR 1202 commercial dimmer cabinet.

In a school auditorium with a 28' ceiling and large can lights with no reflector and 500watt PS52's, we replaced them with GE 88810 32watt PAR38 40 degree LED lamps and achieved excellent brightness and theatre-quality dimming with an old Electro-Controls Quad dimmer rack.

In both cases, we did testing to be reasonably certain of the results but still had compatibility issues to overcome. In the above instances, access was not difficult so you have that problem to deal with.

Very similar Scott.  A bit more ornamental but I'm betting the internals are similar.  I can't say exactly what's going on inside, I've only just seen a spare lamp.  It's glass all around (not sure on the top - can't see that).  I'm going to have a lift in for some other work and I'm hoping to be able to do the retrofit work at the same time but it may end up being an exploratory job and then later doing the actual retrofit.  Fortunately with one fixture out I could actually remove that one for bench work if needed.

I'm not even sure what the dimmer cabinet is on this, suffice to say it's got 4 massive dimmers and is about 3'h x 4'w x 2'd.  It's OLD!  Plenty of space to replace the internals with something modern if needed though!
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Scott Hofmann

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Re: Replacing 750W E39 lamp with Dimmable LED
« Reply #4 on: October 23, 2020, 01:51:45 pm »

I'm all about old dimmers. Would love to see external and internal photos of it!
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Scott Hofmann

Erik Jerde

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Re: Replacing 750W E39 lamp with Dimmable LED
« Reply #5 on: October 23, 2020, 04:19:34 pm »

I'm all about old dimmers. Would love to see external and internal photos of it!

If (when!) I dig into it I'll take some pics.
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Brian Jojade

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Re: Replacing 750W E39 lamp with Dimmable LED
« Reply #6 on: December 08, 2020, 05:15:06 pm »

With LED lights, part of the trick is that dimming them is very different than dimming an incandescent.  An incandescent just needs a lower average voltage and it will be less bright.  The lights work on AC but don't particularly care if they are a clean sine wave, or some random shaped hash (within reason. Some patterns can cause premature failure or ringing of the lights.) 

Because of this, there are a plethora of different types of dimmers out there that work fine with any incandescent light.  However, with LED lights, the light takes line AC voltage and converts it to low voltage DC.  LEDs by their nature are not very dimmable.  Dimming is achieved by pulsing the LED at a high enough frequency that you don't notice it.

The trick for dimmable LEDs is that they have to figure out based on the supply voltage and pattern that is coming in how to convert that AC to the appropriate DC voltage and pulse it at the right rate for it to offer dimming.  As you can imagine, this is a pretty challenging task.  The results are going to depend on the type of dimmer that you are ultimately using and the compatibility of that dimmer with your selected LED.  Additionally, getting different brands/models/revisions of LEDs to dim the same across the same dimmer can be a holy nightmare. 

I've even run into situations where having more than one LED light on the same dimmer as the other can introduce noise into the line to confuse the lights and cause flickering on certain dimmers.

So what that means is if you order bulbs, there's no real way of knowing if they are going to work the way you want until you put them in and test them.
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Brian Jojade

Don T. Williams

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Re: Replacing 750W E39 lamp with Dimmable LED
« Reply #7 on: December 08, 2020, 06:42:31 pm »

I have a HOW customer that was having problems with "dimmable" LED lamps even though they had new ETC dimmers in their new facility.  I don't know if you will have this problem, but their solution (I'm told it came from ETC) was to have a small (10-25 watt) incandesent lamp on each dimmer circuit that contained the dimmable LED lamps.  These were actually hidden in a utility closet and never seen.  This smoothed the dimmer curve and solved their problem.  This may be a solution looking for a problem, but I'm passing it on.
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Erik Jerde

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Re: Replacing 750W E39 lamp with Dimmable LED
« Reply #8 on: December 09, 2020, 02:42:53 am »

I have a HOW customer that was having problems with "dimmable" LED lamps even though they had new ETC dimmers in their new facility.  I don't know if you will have this problem, but their solution (I'm told it came from ETC) was to have a small (10-25 watt) incandesent lamp on each dimmer circuit that contained the dimmable LED lamps.  These were actually hidden in a utility closet and never seen.  This smoothed the dimmer curve and solved their problem.  This may be a solution looking for a problem, but I'm passing it on.

Thanks Don.  I've seen that on Unison racks before when a church I was doing freelance mixing for hired a non-av company to re-do their sanctuary lighting.  It was an after-the-fact oh-shit patch on new lamps.  In my case the dimmer isn't anything nearly as fancy.  I have a feeling I'm going to use one of the drivers Caleb suggested and build a lamp that'll fit the existing fixture.  I'm just in a holding pattern now waiting to get a lift in to get one of them down and onto the bench.
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ProSoundWeb Community

Re: Replacing 750W E39 lamp with Dimmable LED
« Reply #8 on: December 09, 2020, 02:42:53 am »


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