White swich on Durst CLS 301 dichroic head

[rcmartins]

I have slowly been restoring a Durst Laborator 138S with a CLS 301 dichroic head. It is a wonderfull enlarger and I am loving it. One thing that has had me curious from the moment I bought it is the white switch that the CLS 301 head has on the lower right corner. In my enlarger it does not seem to do anything. It probably is malfunctioning but I would like to know what it was for. I am also guessing that it is also connected somehow to the power supply. Mine is a regulated EST 301. I also have the cooling fan. My version of the head is the one with two 300W bulbs.
I have searched the net and this forum, but using the keywords "CLS 301" and "white switch" and some variants I was not able to find anything. The Laborator 138S that Durst USA has kept alive does not have anything on the head but it does make a reference to a booklet that has a title something along these lines: "Durst CLS 301 on the Laborator 138S". Again I have not been able to find it.
Does anyone know what it is for?
Thank you!

[mpirie]

I'm not sure about the CLS301, but the white switch at the side of the CLS450 is used to illuminate the cyan, magenta and yellow dichroic dials at the front of the head so ou can see your settings in the dark.

Mike

[thomas ciulei]

I'm not sure about the CLS301, but the white switch at the side of the CLS450 is used to illuminate the cyan, magenta and yellow dichroic dials at the front of the head so ou can see your settings in the dark.

it's the same for the cls301!

[ic-racer]

Looks like thomas ciulei has your answer. I case anyone else searches for "white switch" on the CLS2000 head the switch turns off the illuminated indicator for "White Light" when the white light lever is pulled.

[rcmartins]

Thank you all. I will now have to find what I suppose is a bulb that is used to illuminate the dials or an empty thread. Again, thank you.

[thomas ciulei]

rc,

from my experience, that switch is more or less useless, the dials, even if lit, are quite dark.
also, who moves the dials in the dark? i always do this with the light turned on after inspecting prints

[rcmartins]

If I am printing B&W you are right, even more so because my timer switches on and off the red light in an automatic way - I am always lit. For RA-4 though the story is different. When making white balance adjustment strips, the amount of filtration must be changed but there can be no light since the paper is on the table and is sensitive to all wavelengths. The fact that it is very dim is actually very good news to me .

[rcmartins]

It is actually a configuration of three very small lamps that are located inside the small black boxes right on top of the middle of the scales for each color. These lamps seem to be neon glow pilot lamps. This would be clever as these typically have an orange spectrum which is one of the safest wavelengths for RA-4. These lamps should be powered by mains voltage. My voltmeter is able to measure the mains voltage in a connection of the wires that go to the switch but on the switch and in the electric connection ruler that derives to the lamps, nothing. Will have to check it further once I disconnect the head from the power supply.

[thomas ciulei]

For RA-4 though the story is different. When making white balance adjustment strips, the amount of filtration must be changed but there can be no light since the paper is on the table and is sensitive to all wavelengths. The fact that it is very dim is actually very good news to me .

can't argue with that