Olite lamps and photocells...

[sklimek]

Hi, I was hoping to open up a discussion on the Olec exposure system in particular the calibration and sensitivity of the lights and photocells.

(I'm not sure if the graphs will open up in this thread so please open the pdf attachment for the graphs supporting this post).



I am currently using an Olite AL53 5K power supply with an LT1 light head and the lamp is the L1250 with the standard baffle, PA 91 photocell and all running on an integrator. I have had good results so far but looking at the specs on the L1261 it seems to be for lack of a better description more ‘full body’ within the 325 to 440 nanometer range.



Here are the specs on the two different lamps:






Here are the Photocells (I am using the PA 91)






As you can see the L1261 is a much broader nm spectrum than the L1250. Digging back into the cobwebs of my brain I believe platinum converts best within the ~325-375 nanometer range.



Looking at the graphs of the photocells it appears that their function is to only allow a controlled spectrum to reach the vacuum frame and can be calibrated more or less.



My questions are even though the lamps put out a broad range is it in fact the photocell that controls the spectrum output and if I did convert over to the L1261 you will notice that it states in the far right column that requires capacitor switch change.



Finally, Olec uses a capacitive ballast instead of a transformer to tune the frequency of the light spectrum:






The reason I bring this up is that in converting to the L1261 it states that it ‘requires a capacitor switch’ which I believe supports the UV spectrum tuning. Has anyone ever done this mod and if so do you recall the part number for this capacitor? I’m sure it is in the power supply and I have the service manual for reference.



Thanx - Stan

 

[bobherbst]

Stan,

The "capacitor change" for changing lamp types is done via a rocker switch internal to the AL53 power supply. The switch positions are described in the AL53 wiring diagrams. See attached jpg. The wiring diagrams used to be available on OLEC's web site. The switch is located inside the front cover and should be visible through the grill above the power and configuration switches. You will have to remove the cover of the power supply to change the switches. Be careful not to touch or short the capacitor leads. The capacitors can deliver quite a jolt if discharged.

The 1261 lamp is broader spectrum than the 1250, but I haven't seen a significant difference in exposure times between them. I've used the L1250 in an AL19 and AL53, and an L1261 lamp in an AL53 unit. I have concerns about the potential damaging effect of the 1261 on skin versus the 1250 if you dodge/burn during exposure. But this is purely subjective personal experience.

Carbon exposures using B&S Ren BLK tissue are about twice the exposure for Pd-NA2 from the same negative. Peak sensitivity of ferric oxalate-palladium-NA2 is at 350nm so in reality, BL tubes are the most efficient light source for Pt/Pd. Still, I prefer the OLEC units and use an AL53 with an L1250 lamp. I used an L1250 in an AL19 for 9 years before that.

Bob Herbst

 

[sklimek]

Just great information Bob - Thanx.