Durst CLS450/500/501/AC1200: shutter?

I got an Durst AC1200 with busted analyzer/control unit, it only allows manual (timer) function. I have some plans about converting the color head to 12V/100W bulb with a new 12V fan installed, so I could throw away the very big and now almost useless control unit. It would be easy to replace the lamp and connect it + replace the original huge fan with one or two 12V fans used for PC's.

However, there is a shutter in all these big CLS color heads, and when the color head is disconnected, the shutter is closed.

I wonder if anyone here knows more about this shutter? There is a small electric motor operating it but does anyone know what voltage it has? Does anyone have a circuit diagram for the CLS450/500/501?

And if I want to simply mechanically disengage the shutter permanently, is it easier to access it from below or from upside?

So if anyone here knows these details of the construction of CLS450/500/501/AC1200 any information would be welcome!

I did find out that the AC1200 color head uses its second set of dichroic filters as a shutter. All three filters in = no light out.

Hello !
I own a CLS450 mounted on a plain Durst Laborator 1000. There is no shuter on this one.
I bet the shutter is inserted between the head and the neg carrige, and is apt to be removed. I doubt there are two heads bearing the same reference and no separate shutter to adapt any head to the AC1200 ?
So maybe you can remove the shutter and, either, mount the head closer to the neg stage ot make a box the size of the shutter one to mount the head without the latter.

The shutter in the CLS1840 and CLS2000 runs off a 24v supply. The complex cam and switches and relay. From what I recall the unit reverses the polarity to the motor unit and it opens the shutter. Then reverses the polarity again to close it. The motor stops on its own (with the microswitches) and 24V stays applied to the board until the polarity is reversed again to open the shutter.

Having said that, none of the info I have on the Durst 4x5 CLS heads describes a shutter. Can you post some pictures?

If you are doing B&W, you won't need the shutter anyway. In fact the major color lab that used my 10x10 CLS had jury-rigged the shutter open all the time when the shutter failed.

You should be able to get excellent results with your intended plan, and just unhook the shutter from the motor and leave it open all the time.

Ok, so I have gotten the false impression that the CLS450/500/501 had shutters?

The only reason I can think of to use a shutter in a color head, is that the bulb doesn't reach it's operating temperature + color temperature instantly, and with a shutter the exposure can be started when the lamp has reached that temperature. This may give better color consistency when the exposure times are short. Is this correct?

I have printed color with a Opemus 5a + Meochrom 2 color head, and never have had any feeling that a shutter would be necessary.

Rollei fan said:

The only reason I can think of to use a shutter in a color head, is that the bulb doesn't reach it's operating temperature + color temperature instantly, and with a shutter the exposure can be started when the lamp has reached that temperature. This may give better color consistency when the exposure times are short. Is this correct?

Click to expand...

The single filament bulb on the 2000W head does take some observable time to warm up (even with the baseline heater current going through it) and it has quite a long orange decay after the power is cut. Back in the day, a Color lab needing to make 20 identical color prints would benefit from the perfection of this system.

In your system I agree with hooking up a generic power supply. Just make sure it has the wattage to handle the lamp you will use. Since the filters in dichroic heads don't wear out, I think it is worthwhile refurbishing color heads. Dichroic heads will outlast two-color coldlight heads.

Sticky filters can be freed up
Bulbs can be replaced or easily substitured
Bulb sockets can be replaced
Generic power supplies can be bought or made
Frayed cords can be replaced
Sealing foam rubber can be replaced
Mixing boxes can be rebuilt and relined with styrofoam
etc...

My workplan for modifying the AC1200 color head:

1) remove or mechanically disengage the second set of dichroic filters (which are now all-in, acting as a shutter)
2) remove the original fan and unnecessary wiring
3) install 1 or 2 12V PC fans + wiring
4) replace the bulb with a 100W/12V bulb, rewire it for the 12V transformer

I guess I will use a PC PSU to drive the fans, then they will be on all the time and cool the lamp after it has been switched off.

After that I could sell the AC1200 control unit for spares.