Durst dichroic heads for the larger Leitz Focomats (IIa, IIc)?

[Lachlan Young]

I was digging around for some information on possible dichroic head options for my Focomat IIa, & encountered a passing reference to Durst having apparently offered adapters for the CLS 201 and other dichroic heads (CLS 450 etc?) to the Focomat II enlargers - does anyone have any literature related to this? I'm especially interested in finding out whether they used a mixing box above the condensers or replaced them entirely.

While I'm asking about Focomat IIa's, does anyone happen to know what the maximum wattage the last generation IIa condenser lamphouse can take? I know that the IIc is rated to 250w, but I'm struggling to get a definitive answer for the IIa.

 

[Hilo]

Lachlan,

I have used a IIa for about half a year, before getting the IIc and used the 250 bulb only two, three times. This was with 30x40cm prints and my exposure times were 25 to 35 seconds and probably with some burning of yet another 25 to 35 seconds. There was no problem. I think the key is to set up the negative fast and if the head feels hot after set up, you wait with exposing a little bit.

 

[Lachlan Young]

Lachlan,

I have used a IIa for about half a year, before getting the IIc and used the 250 bulb only two, three times. This was with 30x40cm prints and my exposure times were 25 to 35 seconds and probably with some burning of yet another 25 to 35 seconds. There was no problem. I think the key is to set up the negative fast and if the head feels hot after set up, you wait with exposing a little bit.

Cheers for this - the IIc manual suggests using a dimmer or similar to lower voltage for setup etc, then turn to full power only for the exposure, which given the 3 hour rated life of the 250w (an over run 150 I'm assuming?) is probably a good idea! I'm used to working with the 600w MG500 head which only lets the focus mode run for 99s at a time, so I'm fine with working quickly then letting things cool off before final exposure. Hopefully I can get decent exposure times with Fomatone...

 

[Hilo]

Probably, in this heating question, there is not much difference between the IIa and the IIc. I do a lot of 50x60cm prints with both IIc and Ic, and use the 250 bulb 25 percent of the time. All I made sure about is to have correct wiring.

As I prefer the original opal bulbs over anything else, this question of (over)heating has been important to me. Perhaps more than anything else. I have a Durst L1000 wall mounted and use the very large opal bulbs, 200, 250 and 300 watt. With this Durst the light uses a mirror to reach the negative and this means longer exposures. Durst made a hole in the lamp-head into which one could connect a flexible tube to blow air in there. I have used this hole to install a small fan and covered this on the outside with a black box that can take air in. I use that fan while setting up and after exposing. Not during the exposure, although I probably could. This works fine. I frequently have basic exposures around 60 seconds, and then again that once or twice for burning. With the use of this fan, there is no problem.

For 135mm negatives the surprising solution came from using the Valoy II for the 50x60cm prints (I modified this enlarger for that purpose). Exposures are a lot shorter with the Valoy II compared to the Ic. This is mainly due to the bulb being much closer to the negative.

Perhaps the above gives you ideas.