Help needed with aristo 1212 cold light

[Ethan]

Hello World!

This is my first post here, so sorry if I made any mistakes.

I recently picked up an old Elwood 8x10 enlarger, and am in the process of restoring it. The enlarger has had several modifications made to it over the years, one being the conversion to an Aristo 1212 cold light head. I don't know much about this head, other than that it is 12x12 and made by aristo, but I opened it up, and it appears to have a single fluorescent tube. it also has a plug which I hadn't seen before, and didn't match any of the power sources at the photo store I got the enlarger from. Photo of that below for reference, how common is this plug?

I also don't have the original power source for this head, I am in contact with the enlarger's previous owner, and he is looking for some components he thinks he has lying around, but in case that doesn't turn up, I may need an alternative to power this thing. I know enough about fluorescent lighting to know that powering it directly from the wall would be a bad idea, so is it possible to use a different cold light power source for it? I'm toying with the idea of modifying a simple beseler enlarging timer with a fluorescent light ballast if I can figure out the specs of the light, but obviously just re wiring it to fit a different power source would be easier.

I tired to find more information on the specs of the lamp, but came up short. the sum of my knowledge on it is basically that the tube has "ARISTO 7452" printed on it, so if that means something to any of you, please share what that meaning is. photo of the fluorescent tube below as well.

Thanks,
Ethan

[David Lindquist]

There are probably others out there that are more knowledgeable than I, but here goes. It is my understanding that the Aristo cold light tubes use a high voltage. I have a hand written note that the power supply for my Model 57 "Hi Intensity" head puts out 2000 volts at 45 ma. I expect your 12 X 12 head also had a separate power supply. That plug is to prevent the head from being plugged in to anything else. I hope the previous owner can find the original power supply, that will certainly simplify things for you!

I don't know what "7452 refers to. I have some early 1970's Aristo literature that describes replacement lamps available in five different colors, "W28", "W31", "W45", "Vari" and "B64".

David

[Pere Casals]

Hello Ethan

https://www.light-sources.com/wp-con...ead_info_0.pdf

If you are to print BW photopaper then cold cathode light requires a calibration procedure: http://www.jbhphoto.com/wp-content/u...ljbharlin1.pdf

Because of spectral nature of the cold cathode light Ilford contrast filters will have a shift, see "Cold cathode enlarger heads" section in page 3: https://www.ilfordphoto.com/wp/wp-co...Multigrade.pdf


Me, what I'd do is directly replacing the tubes by a "Do It Your Self" LED illumination, probably it would take less effort, you won't need antique spares in the future and also you won't need a calibration procedure if you take the right LEDs.

If you use warm white leds of about 3000K color temperature of (say +90) high CRI (color reproduction index) you will have a "standard" illumination that will work fine with Ilford Contrast Fiiters and papers.

I the past tungsten light was provocating a lot of heat and a cold cathode had a thermal advantage at the cost of having a non standard spectrum, today with LEDs you have both the Tungsten bulbs spectrum and no reheating.

________

Instead using warm white LEDs, you may also substitute the tubes by RGB LEDs, using a separated power control for each channel, with that you would have a variable contrast head with no need for filters, you may do split grade printing by making two consecutive exposures, one with Green light and another one with Blue light, by adjusting power/time for each exposure you have different grades, this also allows to burn highlights with lower contrast and shadows wit a higher one. In both the green and the blue exposure you also throw red to see better (for burning/dodging), red it's not seen by the paper, so you expose with yellow (green+red) and purple (blue+red) like with Ilford contrast filters.

But using RGB LEDs may require a calibration work, while using warm white LEDs of high CRI is straighter.

________


So my personal recommendation is that you consider investing in the effort to retrofit the illumination with LEDs rather than fixing the cold cathode gear.

Regards

[LabRat]

Just contact Aristo and ask what is needed, and get a manual for it...

Steve K

[Ethan]

Hello Ethan

https://www.light-sources.com/wp-con...ead_info_0.pdf

If you are to print BW photopaper then cold cathode light requires a calibration procedure: http://www.jbhphoto.com/wp-content/u...ljbharlin1.pdf

Because of spectral nature of the cold cathode light Ilford contrast filters will have a shift, see "Cold cathode enlarger heads" section in page 3: https://www.ilfordphoto.com/wp/wp-co...Multigrade.pdf


Me, what I'd do is directly replacing the tubes by a "Do It Your Self" LED illumination, probably it would take less effort, you won't need antique spares in the future and also you won't need a calibration procedure if you take the right LEDs.

If you use warm white leds of about 3000K color temperature of (say +90) high CRI (color reproduction index) you will have a "standard" illumination that will work fine with Ilford Contrast Fiiters and papers.

I the past tungsten light was provocating a lot of heat and a cold cathode had a thermal advantage at the cost of having a non standard spectrum, today with LEDs you have both the Tungsten bulbs spectrum and no reheating.

________

Instead using warm white LEDs, you may also substitute the tubes by RGB LEDs, using a separated power control for each channel, with that you would have a variable contrast head with no need for filters, you may do split grade printing by making two consecutive exposures, one with Green light and another one with Blue light, by adjusting power/time for each exposure you have different grades, this also allows to burn highlights with lower contrast and shadows wit a higher one. In both the green and the blue exposure you also throw red to see better (for burning/dodging), red it's not seen by the paper, so you expose with yellow (green+red) and purple (blue+red) like with Ilford contrast filters.

But using RGB LEDs may require a calibration work, while using warm white LEDs of high CRI is straighter.

________


So my personal recommendation is that you consider investing in the effort to retrofit the illumination with LEDs rather than fixing the cold cathode gear.

Regards

Thanks for the suggestion, do you know of any tutorials or guides on how to do this retrofit? I'm guessing not just any old LEDs would work

[Tin Can]

Read this thread. https://www.largeformatphotography.i...=1#post1456175

And there are more. I have tried other options. You need to study and search this forum, I have so many posts I can't find mine!

All depends on how intense you are.

Perfection is a disease here.

I experiment.

[Pere Casals]

Thanks for the suggestion, do you know of any tutorials or guides on how to do this retrofit? I'm guessing not just any old LEDs would work

You may use a bare white LED strip



Just use warm white around 3000K, with rated CRI greater than 90, 95 is perfect. Then take an strip with the light power density per length unit that aprox suits the original lamps, when you place all the strip sections that the head would contain, the strips can have a row separation similar than the original tubes, or narrower.

A friend did that in a 8x10 enlarger with perfect results. Me I've replaced the tungsten bulb of a Durst 138 with a warm LED bulb with also perfect results, in my case it was pretty straight. I also use a RGB bulb in the 138 to avoid filters, but until now I've used more the warm white bulb with filters.

[Drew Wiley]

Being incomplete, it's hard to say if the tube grid is still evenly illuminated or even works at all. If you want to restore it, the V54 blue-green tube would be the ideal one for VC papers.

[Ethan]

You may use a bare white LED strip



Just use warm white around 3000K, with rated CRI greater than 90, 95 is perfect. Then take an strip with the light power density per length unit that aprox suits the original lamps, when you place all the strip sections that the head would contain, the strips can have a row separation similar than the original tubes, or narrower.

A friend did that in a 8x10 enlarger with perfect results. Me I've replaced the tungsten bulb of a Durst 138 with a warm LED bulb with also perfect results, in my case it was pretty straight. I also use a RGB bulb in the 138 to avoid filters, but until now I've used more the warm white bulb with filters.

Thanks, it looks like I'll probably go the LED route, as that will last longer and be much easier than trying to get a power source for the fluorescents. I've never done work on a light source before, and don't know the original specs of this cold light, about how many lumens should the source be?

[Pere Casals]

Just the same electric power than the cold light, or more, as you may easily dim the leds if necessary.