Does the bulb say the wattage on it? You could measure the current draw with a multimeter that has a clamp on current capability. It should be around 8.3Amps if the bulb really is 1000W. The meter would just go around one of the wires, which should be accessible near the socket.
If you have a spare bulb try that out. If you don't this may all be moot since the Thorn bulbs are not available new anymore. I don't know if there's a good replacement in that wattage. The smaller ones are rare.
Drew raises a question that's on my mind as well. I'm wondering if you're running into an inverse-square law issue with a combination of small negatives, lens choice, and distance from enlarger to paper.Originally Posted by Drew Wiley
Maybe you're right about the combo of small negative and lenses..
Here's the lenses we have. I did slap some Nikon lenses into the durst lens boards.. maybe that's the issue? So far, I've only tested the enlarger with the 50mm and the 105mm. Again those are Nikon lenses that I put into the Durst boards, because the 50mm and the 105mm that were given to me with the enlarger were in rough shape.
Perhaps I'm using the wrong lens boards for the focal lengths? Because there's some that are recessed about 3".
If you can focus the lenses it shouldn’t matter which lens boards they are mounted to. The purpose of the recessed lens boards is to hold the lens and position it close enough to the film for the focus to be possible. As long as that is met the brightness of the projected image will be the same between boards.
Are you adjusting the position of the bulb so it is correctly centered and the right distance from the film? That makes a big difference in how even the image is and maybe if it’s off enough could be cutting down the light.
Can you setup for a 4x5" to 32x40" with the 150mm at f5.6 and take an incident meter reading. I can compare to my Durst with the same settings.
Unfortunately, I've never bothered with condenser heads, so can't give a specific answer online. I have one in storage somewhere. But I have rebuilt several large Durst colorheads and commercial chassis, and am using those. I have no doubt that upgrading a housing and lamp source like the one in question would be fairly easy for me if I had it in my own shop; but conversion and recommended rewiring should done by someone with prior experience or at least a knack for it. Trying to rely on arcane old opal bulbs is futile. Even if it works out, that won't be the answer for very long. Or you might be able to afford a used actual halogen colorhead like the CLS 301, provided that itself doesn't have repair issues.
These are the kinds of things you should discuss with someone like Glenn Evans.
I will, however, point out another helpful trick. You can often use a longer than normal focal length at fully wide open aperture since only the center of the optic is being utilized. For example, I have sometimes used a 105 Apo Rodagon N wide open at f/4 for little 35mm film. That might not work so well with older less corrected lenses; but it is something to keep in mind.
Totally sure the lens aperture is wide open, and not all the way closed down?
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