Aristo cold light question..

[Robbie Bedell]

I recently bought an Aristo cold light for my D2 enlarger. I have had one once before, a Zone lV. I bought this head for a project which requires printing old negatives which have been attacked by mold. This bulb is the older v45 so I have the yellow filter in it and that part works just fine. My problem is that I am getting inconsistant exposures. After I make a test strip of say, 10 sec. and determine I need a nine sec. exposure, I make my print at the nine sec. I then make a second print at the same 9 sec. and it is sometimes darker and sometimes lighter, by at least one whole stop. I know there is a heater in the head to keep the bulb warm. The heater cord is plugged in. Is it possible that the heater is not working? After it has been on for some time I touch it and can feel no heat whatsoever. Perhaps I have a voltage variation problem. Can anyone suggest a simple voltage regulator, if that might be the problem. This is frustrating because I do like the results I am getting when things do work out. I am not new to printing. I have been printing on my two D2s and focomat for many years and worked for newspapers for more than 20 years and never had such a variation in times without being about to troubleshoot the problem. Can anyone help!

http://robbiebedell.photoshelter.com

[Kodachrome25]

Hi Robbie, you will relieve your self of the headaches of a Aristo Cold Light Head if you use a compensating timer with the sensor which reads the true output of the lamp in real time and then feeds that info directly to the timer.

There are a couple options, one hard to find, one easy. The hard to find one is a Metrolux-II compensating timer with probe which is no longer made and pops up on eBay only on occasion. Then there is what I now have and that is a RH Designs StopClock Vario (http://http://www.rhdesigns.co.uk/darkroom/html/stopclock_vario.html) with probe and is truly excellent. The Vario uses the popular "F-Stop" method of exposing paper, a bit of a learning curve but after no time at all, it all makes sense. Richard is great to deal with and his products are superb, in addition to the Vario, I own the paper flasher and process timer.

The Vario is by no means cheap, but it works out to saving money in paper and frustration in the long run. That is what I did and there is no going back, it just works...

Worse case, you buy and use the Vario just for the project, then if you feel like it, sell the timer and the head as an enticing package and will most likely still come out ahead in paper and time savings...

Good luck either way you go!

[Jon Shiu]

One possible thing to try is to leave the bulb on so that is warm. Turn it on 10-15 minutes before printing. Have to work out a way to block the light with a lens cap or red filter when loading the paper into the easel. Can use a hand held card to block the ligtht when removing the cap or filter to start/end the exposure.
Jon

[Doremus Scudder]

One possible thing to try is to leave the bulb on so that is warm. Turn it on 10-15 minutes before printing. Have to work out a way to block the light with a lens cap or red filter when loading the paper into the easel. Can use a hand held card to block the ligtht when removing the cap or filter to start/end the exposure.
Jon

Ditto! I used this method successfully for years. The only downside is a bit shorter bulb lifespan. I print using a metronome, so it was easy to just cap the lens, put the paper in the easel, hold a card under the lens, start the metronome, remove the cap and then pull the card to start the exposure.

If you use a regular timer, you can do the same, just set the timer for a few seconds more than you need and pull the card at the appropriate moment.

If you have an enlarger that leaks light (as most do), you may want to rig some baffles to keep stray light from bouncing all over the darkroom. I just cut up some of the lightproof paper bags and hung them with tape from strategic point on the enlarger.

Do turn on the head 15 minutes or so before making your first exposure, as Jon advises.

Best,

Doremus

[Brian Ellis]

You might be able to find an enlarging meter like the one Ilford makes or used to make. Mine cost about $25 new. I found that I didn't need it with my Aristo VCL4500 head so I seldom used it and don't remember the details. But IIRC it was pretty simple to use.

I owned the Metrolux II timer someone mentioned. Mine cost about $250 new about 15 years ago. I don't know what used ones sell for today if you can even find one. However, IMHO they're overkill for your problem, which sounds mostly like a stabilization problem. I bought mine mainly with the hope that it would allow me to go from a small print to a larger one without having to re-test or re-check the exposure, dodge, burn, etc. times. It worked less than perfectly for that purpose.

[Robbie Bedell]

Thanks so much for all of your information! It appears that the best solution would be to find a compensating timer someplace. But what I don't understand about this unit as it is, why if it has a built in heater which I plug in a half hour before printing, why it doesn't keep the bulb warm already without having to keep the bulb on? What is also strange is that sometimes the exposures are fine. I did a test yesterday and made three prints of the same neg and they were all fine. Then the next neagtive the times were not consistant. I may just go back to the Ilford 400 that I used earlier..Thanks you all again for your wisdom!! Robbie

http://robbiebedell.photoshelter.com

[Joseph Dickerson]

Robbie,

You don't say what timer you're using but the power requirements of the Aristo heads is too great for many enlarging timers. It actually fries the contacts. Hence, the timer will very quickly become unreliable, this might be what you're experiencing. A relay between the timer and the head will solve the problem, as will using a proper timer. Aristo used to have a list of which ones would work, I believe that the mechanical Time-O-Lites were fine. Many electronic timers simply couldn't handle the load.

If the head is not warm to the touch, not hot mind, just warm, the heater is not working and could also cause the problem you are experiencing as the tube will increase it's output as it warms.

Leaving the lamp on and using a card to block the light as Jon suggests, and an inexpensive metronome for timing will allow you to check if the problem is your timer or a heater issue. To me it sounds like it's a combination of both.

JD

[ic-racer]

Is it possible that the heater is not working? After it has been on for some time I touch it and can feel no heat whatsoever.

I'd say that is the definition of 'not working' :)

Check the thermostat and the heater elements for continuity. In my Aristo, the heater elements are just power resistors shorted across the mains.
http://img.photobucket.com/albums/v670/ic-racer/powerresistors.jpg

[ic-racer]

When the heater is working correctly, you should be able to get excellent repeatable results by allowing the temp to stabilize between prints.
http://img.photobucket.com/albums/v670/ic-racer/IntensityTemp.jpg

[SpeedGraphicMan]

Sounds to me like the heater is DOA.

You can repair it... Or just leave the unit on while using it...

A lens cap for your enlarger comes in handy in this instance.

[Robbie Bedell]

Thanks everyone! Joseph, The timer I am using is a Gralab 500 and I think it can take the load of this lamp, I least I read that someplace. I will open the light up and look inside tomorrow. I am not much of an electrician but I am hoping I can make the fix on the heating elements. This is the 4x5 round lamp. Wish me luck!! Robbie


http://robbiebedell.photoshelter.com

[Chuck Pere]

Don't forget the obvious and make sure the heater AC outlet works OK. If the thermostat is bad and not closing maybe you can get a replacement from Aristo. Checking should be easy if you have an AC voltmeter.

[Robbie Bedell]

Well, I opened it up and this baby is very old. There is a stamp that dates it to April 1983. I am sure parts are impossible to find. It looks like there is a resistor (where the red wires lead). I blew the fuse on my voltometer a while back. Would it be safe just to bypass the relay altogether? I don't know why it would need a relay at all, for something that just stays on for hours and hours. As I said I am no electrician. I am going out to get a fuse, but I can see nothing else that could go wrong. The heater just looks like a plate that sits underneath on the top of the lamp casing. Thanks for all of your patience on this!! Robbie

http://robbiebedell.photoshelter.com

[Neal Chaves]

You don't need special compensating timers to get consistent results from a cold light head. All bulbs, even filament bulbs, take time to reach full brightness when power is first applied. If you make a test strip with a series of five second exposures and then pick twenty five seconds as the best time, your twenty five second print will be dark. That's because each of those five second bursts equalled only about four seconds of effective exposure. To make an accurate test strip with any type head, use an audible timer and a large card. Set the timer for the about twice the longest possible exposure so you can see the result of burning in certain areas. For example: set the timer for 60 seconds when making an 8X10. Cover the whole sheet except for one inch. Start the timer and count seven beeps (It beeps when you start) then move the card one inch for the next six beeps and one inch every six beeps after that. The end result will be a ten level test strip of six seconds each from six to sixty seconds. If you then pick thirty seconds as the best exposure, your thirty second print will match the test strip.

[Robbie Bedell]

Thank you Neal


http://robbiebedell.photoshelter.com

[ic-racer]

In terms of darkroom equipment 1983 would be pretty recent. The head looks very good inside. So, verify that the thermostat is working, it probably just needs to be adjusted. I'd set it to around 40 degrees C and go from there.

The best way to get consistent results is to use little pieces of paper one at a time. Guess at the exposure and process the little piece of paper, and go from there. If it is too light then double the exposure, and so on. You are going to have to guess the exposure anyway even if you use a 'test print.'

[Bill Burk]

I certainly feel your pain.

I found the problem was the "pattern" of my use...

I used to "focus" and compose for several minutes, then turn off the lamp, take a test strip out and hide it behind my back, hit the "focus" switch for a couple seconds while I aimed and then turn it off and put the test strip on the easel. Then I'd get out the cardboard, hit "expose" and count off a few third-f/stops while moving the cardboard. This tended to make test strips while the lamp was "warm".

Then the lamp would cool down during the next phase of my work which might take ten minutes or so... Develop the test strip (three minutes), stop it and fix for a couple minutes, turn on the light, look at the test strip and think what to do next.

When I'd make a final print the lamp had cooled down. The light changed so the print wouldn't match my guess. Same problem you're having.

---
My "solution" was to put a sensor in my lamphead and connect to an ohmmeter. This gives me a number that relates to lamp brightness. I can watch the number changing and stabilizing and adjust my work pattern to work with the lamp while the ohms reading is fairly stable.

It's improved my consistency, though a bit fiddly to recommend anyone else.

---

Bottom line: Pay attention to lamp brightness and how long it takes to warm up to operating temperature. Work with it while it is stable.

It was simple to change my work pattern...

I just turn on the focus for a couple minutes before making final prints... to make the lamp as warm as it was when I made my test strips.

I really like Doremus Scudder's advice to leave the lamp on... But I get squeamish about leaving lamps on.

[Doremus Scudder]

...My "solution" was to put a sensor in my lamphead and connect to an ohmmeter. This gives me a number that relates to lamp brightness. I can watch the number changing and stabilizing and adjust my work pattern to work with the lamp while the ohms reading is fairly stable.
...

I really like Doremus Scudder's advice to leave the lamp on... But I get squeamish about leaving lamps on.

If I had Bill's ohmmeter, I would just find the point on the ohmmeter where the light stablilizes, and then, before making any test strip or print, simply flip on the light and wait until the ohmmeter showed the light was stable (that's basically what the Zone VI stabilizers do). FWIW, I now print with color heads or a cold light with a Zone VI stabilizer.

That said, in lieu of a sensor/ohmmeter/stabilizer, just fire up the head 15 minutes before your printing session and turn it off after you make your last print for the day (or turn it off if you are not going to use it for half an hour or more, e.g., breaks). Even with the light on the entire session, it will only be on a few hours a day usually (my longest printing sessions are 6-8 hours, but a lot of that is prep / washing / toning, etc. when the enlarger light could be off).

When actively printing, keep the light on and just keep the enlarger lens capped when not exposing paper. You just need to find a way to deal with timing exposures, not really an insurmountable problem. No need to be squeamish :) (sorry Bill, couldn't resist)

Best

[Robbie Bedell]

Again, thanks to all. I checked all of the wiring and measured the current with my voltometer and I am alive to tell the tale. I am just checking the heating wire. It appears that there is power right down to the heating plate that is sort of glued to the top of the lamp just above the bulb. But after plugging it in far a half hour or so there still is no heat the be felt, so I guess that part of the heater is not working even though it has power. I have been in touch with Louise Kessler at Voltarc but am a really getting nowhere. Is anyone familiar with the heating plate and is that something I can find? I think I would be able to replace it if I could get the part. My electrical skills are improving thanks to you folks!! Robbie


http://robbiebedell.photoshelter.com

[Robbie Bedell]

OK folks. We can end this whole thread as I just have just bitten the bullet and bought a very nice looking cold light, a much newer one, which I will use to replace this old one and hopefully my problems will be solved and I will spend the rest of my days in darkroom nirvana.. I just want to thank all of of you for the advise you have given me. I have visited and looked at the work of those of you who have provided links to your sites, Doremus and Jon. I think it is truly great work. I wish you all the best of luck...Robbie


http://robbiebedell.photoshelter.com

[ic-racer]

You can ( and Aristo did) use power resistors for heaters.
Here are some links to help you out:
http://www.digikey.com/Web%20Export/Supplier%20Content/Riedon_696/PDF/riedon-an-resistors-as-heaters.pdf?redirected=1
http://www.caddock.com/whats_new/MP9000_press_release.pdf
http://www.edaboard.com/thread252511.html
http://builders.reprap.org/2009/01/ceramic-resistors-as-low-tech-heater.html

[Robbie Bedell]

Thanks Ice, but I just bought a new model cold light. But I will visit your links tomorrow. If I can fix this old one I will sell it. Robbie

http://robbiebedell.photoshelter.com

[Eric Woodbury]

Metrolux is still available from new stock.

http://meteredlight.blogspot.com/