Omega Super Chromega C - LED Bulb Replacement?

[Alexm920]

My buddy recently inherited a darkroom complete with an Omega Super Chromega C enlarger (the enlarger itself is a C67). While checking it over, the lamp burned out, and both replacements we got ahold of burned out the instant we supplied power to them. At this point we're suspecting the power supply is at fault, due to component aging, but rather than dive into that, we were considering replacing the lamp with a modern LED bulb, and simply powering it from an outlet+timer. The longer life, lower operating temps, and ability to work without the stock power supply appear to make it a winner.

From what I've read in other threads, a color temperature around 3000K is decent, with an output of 50-150W (incandescent-equivalent, actual power is usually ~5-15 W). Given the light passed through the dichroic filters, then the mixing box, I'm less concerned about total uniformity.

The hard part is finding a bulb / socket combination that fits correctly in the lamphouse. We've measured the current bulb and housing. There's a retaining clip about 2" from a plate with a circular hole, full-diameter just under 2". With the original bulb, this clip pressed the bulb against that plate to hold it in place.

Has anyone solved a similar problem before? In other threads I've seen bulbs suggest, e.g. Dead Link Removed, but it doesn't seem like I can order one within the US.

Images: https://imgur.com/a/kKCJu

 

[spijker]

Do you know the wattage of the original burned out lamp? The LED bulb in your link is only 350 lumen which won't be enough. The type of halogen bulbs used in these dichroic head enlargers is approx. 20 lumen/watt. So a 100 W bulb produces approx. 2000 lumen. As far as I know, there are no small reflector GU10/MR16 LED bulbs available that are that bright.

 

[Alexm920]

Do you know the wattage of the original burned out lamp? The LED bulb in your link is only 350 lumen which won't be enough. The type of halogen bulbs used in these dichroic head enlargers is approx. 20 lumen/watt. So a 100 W bulb produces approx. 2000 lumen. As far as I know, there are no small reflector GU10/MR16 LED bulbs available that are that bright.

The bulb that burned out was a #471-033 Quartz Halogen Reflector Lamp rated for 150W at 21V, given your rule it thumb it likely put out quite a lot more than the one that was suggested in the previous thread. That said, other users have reported reasonable exposure times using these style of bulbs, so I was hoping to see if anyone tried this with something similar to the Super Chromega with it's relatively cramped lamp compartment. Even if we can only substitute in a dimmer source, I'd be fine with bumping up the exposure time for printing accordingly.

 

[Sirius Glass]

I found two brightnesses of bulbs for my SuperChomega at FreeStyle. Give then a telephone call.

 

[spijker]

The bulb that burned out was a #471-033 Quartz Halogen Reflector Lamp rated for 150W at 21V, given your rule it thumb it likely put out quite a lot more than the one that was suggested in the previous thread. That said, other users have reported reasonable exposure times using these style of bulbs, so I was hoping to see if anyone tried this with something similar to the Super Chromega with it's relatively cramped lamp compartment. Even if we can only substitute in a dimmer source, I'd be fine with bumping up the exposure time for printing accordingly.

As far as I can see, the users in that thread all use condensor heads and not dichroic heads. The condensor heads typically take a round incandescent bulb and not a halogen reflector bulb. Incandescent bulbs are less bright so that and the larger form makes it easier to replace them with a LED bulb. The bulb that Ron789 uses outputs 1055 lumen but it radiates in all directions. The condensor heads are designed to accommodate that. In your (and my) case the light needs to be squeezed through a approx. 1 inch hole between the reflector bulb and the dichroic filters. So you'll need something that gives you a bright and concentrated light beam. You can try a GU10, PAR20 or MR16 (12V !!) reflector bulb but I'd suggest to find something that is at least 600 lumen and 3000..4000K. Narrow-beam is better than flood. You can also experiment with the bigger PAR30/38 bulbs that use one COB (disc) LED in the center. Not ones with a multiple LEDs distributed over a larger surface. But you'll likely have to modify the enlarger lamp house for that.

I recently tried out this bulb to get an idea on how much lumen I need in my LPL 670 enlarger. It normally takes a 100W 12V bulb. The 620 lm LED bulb is 1.5 stop less bright then the 100W halogen bulb. Haven't printed with it yet.

 

[DREW WILEY]

LED's aren't continuous spectrum. So you're off on the wrong foot to begin with in a colorhead using CMY subtractive filters. It could be a failing power supply, corrosion on old bulb contacts, fingerprint oil on a new bulb, or just the fact you bought a junky bulb from some El Cheapo store. If the bulb pkg says, Made in China, avoid it.