Halogen bulb confusion for Chromega

ac12 · Jan 8, 2014

My Omega D5 color head bulb spec is for 250w 24v halogen bulb, and an Omega part number.

I've seen references to ELC and ELC-E bulb for this enlarger.
But even in the ELC family there are many variants ELC-3, ELC-5, ELC-7, etc.

I am also confused as some of the bulbs are rated at 50 hours, and others at 500 hours.
Is the 50 hours many on/off cycles, vs 500 hours more continuous burning?
All things being equal (which they probably are not) I would go with a 500 hour bulb over a 50 hour bulb.

So what do I go with?

thanks

Tom1956 · Jan 8, 2014

For my small portion of contribution to the quest, I bring up that it is the amount of actual on-off cycles that contribute most to the longevity problem. Thermal shock has killed more bulbs than continuity of burning. Face it, bulbs are 1 thing they sure don''t make like they use to. They use to use tungsten, so is said. Lord only knows where your modern third world bulb comes from or what is in it. Concentrate on the question of light evenness from the replacement bulbs or bulb sets. But then, with color heads that use mixers, then only bulb length can come into play. Wattage goes without saying; it is set in the operator's manual.

Neal · Jan 8, 2014

Dear ac12,

My Chromega head came with a bulb that used a smooth reflector. Further, the ones that are noted as being for enlargers and projectors seem to be rated at 3400K but also seem to be rated at 50 hours. I have settled on bulbs with those two ratings and have had no issues. Just to stir the pot a bit though, when I first got the enlarger (cheap basket case) it came without a power supply so I re-wired it to use in an ELH bulb (120V 3200K). This worked fine for both b&w and color for more than a year. Then I had an issue with color printing I couldn't resolve, I cobbled together a power supply and rewired the enlarger to the original specifications. The new system was brighter, but of course the real problem was due to operator error.

Why did I bring all that up? Because it probably doesn't really matter which bulb you choose.

Good luck,

Neal Wydra

mgb74 · Jan 8, 2014

Tom1956 said:
For my small portion of contribution to the quest, I bring up that it is the amount of actual on-off cycles that contribute most to the longevity problem. Thermal shock has killed more bulbs than continuity of burning. Face it, bulbs are 1 thing they sure don''t make like they use to. They use to use tungsten, so is said. Lord only knows where your modern third world bulb comes from or what is in it. Concentrate on the question of light evenness from the replacement bulbs or bulb sets. But then, with color heads that use mixers, then only bulb length can come into play. Wattage goes without saying; it is set in the operator's manual.

Which raises the question of whether it would be better to come up to full voltage somewhat gradually. And, if so, should we look for a way to do this as bulbs become more scarce?

ic-racer · Jan 8, 2014

Which raises the question of whether it would be better to come up to full voltage somewhat gradually. And, if so, should we look for a way to do this as bulbs become more scarce?

The Durst CLS2000 has filament preheat, which might be something you could implement. There is always current going through the bulb, but not enough that it lights (though it uses an electronic shutter to time the exposure).

In terms of the Chromega and reflector style. I have not tested that head, but I did test another 6x7cm dichroic diffusion head with different bulbs and did not detect any change in illumination evenness based on the bulb's reflector.

mgb74 · Jan 8, 2014

I was thinking of something along the lines of a rheostat (essentially a dimmer switch) to lower voltage. Although probably not such a good idea for any equipment with electronics in the circuit.

Ian C · Jan 8, 2014

The Omega dichroic heads that use the ELC lamp operate at reduced voltage by design.

The winding ratio of the transformers in the Chromega D Standard Power Supply, Chromegatrol, Chromegatrol II, and Super Chromega F Power Supply have been selected to produce a 6.25% voltage reduction to prolong lamp life and help prevent blackening of the inside of the glass envelop (gets plated with evaporated filament material). Thus the 250-watt 24-volt ELC lamp (4 lamps in the F head) operate at 22.5 volts in the Omega dichroic color heads in the list above.

Tom1956 · Jan 8, 2014

mgb74 said:
I was thinking of something along the lines of a rheostat (essentially a dimmer switch) to lower voltage. Although probably not such a good idea for any equipment with electronics in the circuit.

Agreed. Not a good idea.

L Gebhardt · Jan 8, 2014

Ian C said:
The Omega dichroic heads that use the ELC lamp operate at reduced voltage by design.

The winding ratio of the transformers in the Chromega D Standard Power Supply, Chromegatrol, Chromegatrol II, and Super Chromega F Power Supply have been selected to produce a 6.25% voltage reduction to prolong lamp life and help prevent blackening of the inside of the glass envelop (gets plated with evaporated filament material). Thus the 250-watt 24-volt ELC lamp (4 lamps in the F head) operate at 22.5 volts in the Omega dichroic color heads in the list above.

And some people said I was crazy for doing effectively the same thing with a variac for my Durst bulbs. I now feel somewhat vindicated.

ic-racer · Jan 9, 2014

Ian C said:
The Omega dichroic heads that use the ELC lamp operate at reduced voltage by design.

The winding ratio of the transformers in the Chromega D Standard Power Supply, Chromegatrol, Chromegatrol II, and Super Chromega F Power Supply have been selected to produce a 6.25% voltage reduction to prolong lamp life and help prevent blackening of the inside of the glass envelop (gets plated with evaporated filament material). Thus the 250-watt 24-volt ELC lamp (4 lamps in the F head) operate at 22.5 volts in the Omega dichroic color heads in the list above.

Interesting. The D5500 service instructions instruct one to crank the voltage on the 82V EYA in that device right up to 82.0V. I had considered lowering the voltage but, in 14 years of using D5500 components, lamp life has not been an issue for me.

DREW WILEY · Jan 9, 2014

The exact reflector pattern of the ELC bulb is relatively unimportant, because the diffusion chamber will even things out. What is important is
the basic quality of the bulb. Spend the extra bit to acquire true US or Japan mfg bulbs. The cheap Chinese imports are exactly that - cheap -
and won't last long at all. I prefer Ushio bulbs and probably only need to change the ELC once a decade, or even at longer intervals. Some
cheap bulbs won't even last a month.

John Weinland · Jan 19, 2014

My stock (no electrical mods) D5 uses the ELC-SY bulb which can be used in overhead projectors, and has a dichroic reflector surface. Other ELC variants are clearly not for optics applications (pool lighting, entertainment &c). Perhaps the ELC-SY do not last very long, but at under $10 each from www.bulbdirect.com you can afford to have a few spares.

ac12 · Jan 19, 2014

Thanks guys, I think I will go with a plain ELC, and I will look for the Ushio, GE, Sylvania or Phillips. But for the non-Ushio, I think I need to have the bulb in hand to see the "made in..." printing. So is there any value in going with a major brand w/o seeing the package?

Neal · Jan 20, 2014

Dear ac12,

It just doesn't matter. Order it with a film or paper you always wanted to try and you might save a bit on shipping.

Neal Wydra

Jim Taylor · Jan 20, 2014

My experience with this lamp in a De Vere dichromat IV head is that the colour temp of the cheap (50 hour) lamps drifts a little over time...

The 500 hour lamps seem more stable for longer. Nothing too serious, just need to be aware of it and correct the filter pack.

ath · Jan 20, 2014

The rated life of a bulb depends on the temperature of the filament. This temperature gives the colour temperature of the light. The higher the temp the shorter the rated life.

(there was a url link here which no longer exists)

gleaf · Jan 20, 2014

Some crevice of brain thinks that bulbs are color temperature stabile to 80% of their rated life. Tucked next to that is a photo flood letter code. Likely true for all conventional bulbs.

Halogen bulb confusion for Chromega

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