By the way, if anyone is interested, I'm about to buy a whole darkroom setup from a guy, keep some stuff and sell the rest, including another Thomas Duplex, so if you are in the market, shoot me a PM. I'm sure the filters will need replacing!
I tested my Duplex safelight and found that I had to close the flaps.
We have 3 Thomas units in our college darkroom. The darkroom is about 15' x 30' and the lights are spaced about 10' apart. They are about 1' below and bouncing off the ceiling with the vanes open approximately 1/3 of the way. When I'm working in there alone I usually close the vanes because I prefer it dimmer than the students. (sic) The brightness sometimes interferes with seeing the projected image at smaller f/stops when burning/dodging.
The only other complaint I might have is that sometimes the lamp contacts get corroded and stick to the socket making the lamp hard to remove. It is awkward to begin with and if the lamp is stuck, very difficult to remove. But then I've only had that problem twice and have only replaced about 5 lamps between the 3 units in 22 years. And that's with them burning about 55 hours per week. They are a very good investment IMO.
I have experienced some fogging with ortho materials so I have a couple 10" x 12" safelights with 15w incandescents and 1A filters directly above the sink areas when I'm doing ortho and have the Thomas' shut off.
My dumpster dived Thomas Duplex hums:(
Can't hear my radio it's so loud. Is there a fix?
I'm pretty sure there is a starter ballast in there. It may need to be changed.
Here's some info that I thought might be interesting. This may all be common knowledge, but hopefully useful to some.
The Thomas Duplex safelight was offered with various filters for different uses. Most of us at APUG are going to be interested in the versions "Type DUB" for black and white printing and ortho processing, or the "Type DUC" for color printing. To the best of my knowlege (and personal experience), the Type DUC is also fine for standard black and white printing (but not ortho film processing) .
The only differences are the filters fitted, and the information below explains the tape color codes that indicate the use for each filter.
This is excerpted, paraphrased, or interpreted from literature from Thomas Instrument Co.:
Black and White Printing (Type DUB)
Yellow filters in the housing and Red in the vanes (that refers to the color of the taped edge of the filter). Vanes can be fully open in a large darkroom (they indicate 12 x 14 feet with "standard" 9 1/2 foot ceiling height and the bottom of the safelight 7 feet high). Being able to use the vanes fully opened would obviously depend on how close the installed safelight is to areas where paper is handled. The vanes should be closed as much as necessary to prevent fogging for the exact darkroom size and conditions.
Ortho Processing (Type DUB)
"For Ortho Films, papers and most graphic arts materials, the vanes should be fully closed so that the light passes through the yellow and red filters. If the light level is much lower than desired, it may be raised substantially by removing the yellow filters and using only the red ones in the fully closed vanes. Make certain the vanes close tightly to avoid leakage of yellow light."
Color Printing (Type DUC)
Yellow filters in the housing and Black (black tape edge) filters in the vanes. "For color printing papers, the vanes should be fully closed, so that light passes through the yellow and black filters. The light level will be rather low, bu t still many times brighter than conventional safelights. ..."
My Thomas safelight has been "humming" along for about 3 years now. The noise is a bit of a bother, but I'm waiting for the bulb to burn out before replacing it, plus, I have a back up Thomas. Does anyone know what type of ballast and where to pick one up? I suspect the ballast is more the culprit than the bulb, could be wrong, but would like to find a replacement just in case.
I am curious where you got the information about the transmission and cut-off for the filters used in the original Thomas Duplex. I want to find replacement filters for the color (black) filters.