Aristo Cold Light Head- Heat Build Up?

[elaine_w.]

Hello, I own an old Beseler 4x5 enlarger (the one with the motorized

chassis). I just recently bought a used Aristo cold light head off

an auction site. It had no instuctions with it. On the front of the

head it reads, "Aristo, D-2 HI". There are two plugs, one of the

plugs hs a tag that reads "Thermo Cord". I installed the head on my

enlarger and plugged the thermo cord into an outlet and the other

cord into a very old Time-O-Lite timer. I left for about an hour and

when I came back to start printing, the cold light head was very,

very hot to the touch. I immediately unplugged everything and after

a while, I was able to tell that with the Thermo Cord plug unplugged,

the heat went away. I have only used it a few times and I am having

weird problems with consistent exposures from the same negative using

he same fstop and time. Any help at all would be greatly

appreciated. I have been shooting LF for a while now, and I process

my own film using dip and dunk tanks, but I am fairly new to

printing. I shoot only TMax 400. Thanks, Elaine W

[michael_veit]

I've got an Aristo D-2 cold light and after much frustration in getting inconsistent print results like you describe, I started leaving the light on for the entire printing session, only turning it off for the short time it takes to put paper into the easel. Sometimes that means it's on for 6 hours or more and it does get hot, but after two years it's still going strong.

[matt miller cambridge, ia]

The thermo cord should be left plugged in during your entire printing session. It keeps the bulb warm to ensure more consistent printing. Your inconsistency is probably caused by the different light intensity output as the bulb warms during exposure. I have the Aristo D-2 HI and leave the thermo cord plugged in the entire printing session. I don't notice the inconsistency you speak of.

[jnanian]

hi elaine

 

you might want to get intouch with aristo -

their website http://www.aristogrid.com has their phone number - ask for rick.

you can have a new tube installed and everything checked out at the factory for

something like 100.00.

[william_whitaker1]

If the head is, as you say, <I>"very, very hot to the touch"</I>, that does not sound right. I would suggest that for safety's sake you do not use the unit until you've had an opportunity to contact Aristo as already suggested.<P>

 

The Thermo cord is wired to a pre-heater, a small heating unit above the grid lamp in the head. Its purpose is to help keep the lamp in a temperature range where its light output is more consistent. I've used a number of Aristo heads, but admittedly not one of the "HI" output heads. It's possible it's intended to run warmer than the other types, but your description makes me wonder if it's operating normally or if, perhaps, a short may have developed across part of the heating unit.<P>

 

Regards,<BR>

Will

[philip_sweeney]

There is a small thermostat and resistor inside. The lamp should be very warm not very hot. Sounds like a defective thermostat. If you are a do-it-your-selfer you can get a replacement.

[elaine_w.]

Thanks to everyone for the help. Now that I think about it, I was able to leave my hands on the outside of the head for a few seconds so I was probably wrong in my first assesment that it was very, very hot to the touch. It makes sense about keeping the lamp warm. I will try printing that way and see what happens. Thanks once again for the help. Elaine W.

[User_503771]

This is an age-old problem with cold light heads: Varying light output.

 

The problem is that the gas in the tube changes characteristics as it's left on, thus the light output changes over time during a printing session. Add in spikes in voltage and you've got a real mess.

 

I remember in the early '80s reading Fred Picker's newsletters about this subject. He teamed up with a scientist he met at a workshop and they worked out the "compensating timer", which is basically a computerized set-up which measures the actual light output and adjusts output voltage "on the fly" as you make an exposure.

 

Ansel Adams bought one and was very happy with it -- he'd had the same problems with cold lights. I believe I recall that Paul Caponigro also bought one and was happy with it, according to Mr. Picker.

 

These were made for years by Zone VI. I believe that Calumet has taken over the line and still produces them.

 

Zone VI also made a less-expensive version called the "tick-tock" which measured light output and adjusted gaps between beeps. So you have one second's worth of light coming out between each pair of beeps, assuming the timer is adjusted to beep every second. So you get a weird-sounding early-computer-speaker beep. The nice thing about beeps and timers is that you don't have to watch the clock, but can count instead while looking at the print you're making. And the "tick-tock" was substantially less expensive than the compensating timer, but does basically the same thing.

 

In any event, if you don't smell any foul electrical smell while your light is on, it's probably okay, but I would find some way to measure the temperature on the case and then contact Aristo just to be safe. They probably have temperature specs to compare to. An inexpensive digital room thermometer from Radio Shack might do the trick for this; just hold the electrode against the case and you'll have your temperature reading.

 

Hope this helps.

 

'Bye for now,

 

--Michael Hendrickson

mhh@pacbell.net

[tom_johnston4]

I use two heads like yours and I have never had a problem with them getting anywhere near what you would describe as being hot. As someone else suggested, I think it would be a good idea to stop using the head until you have it checked out. Also, as someone pointed out, you should leave the heater plugged in.

 

Unlike some others, I have never had a problem with output inconsistency either. And I live in an old house and while I'm printing my washer is running. It drains into a sump and a sump pump is cycling on and off which could cause voltage fluctuations but my prints are still beautifully consistent. Go figure!

 

(You may find it interesting to know that the scientist that someone mentioned above who designed products for Fred Picker is Dr. Paul Horowitz. He also designed the Zone VI modified meters and other useful products. He is the scientist in charge of SETI - Search For Extra Terrerstrial Intelligence. No...he is not some crackpot. He is a Harvard professor who uses a large array of huge radio telescopes and stuff that searches for unusual radio waves originating from space. If you watch PBS shows, you have almost certainly seen him in NOVA specials, etc. Interesting guy.)

 

Once you are confident that your head is working properly, you may want to get a voltage regulator. You don't even need one made specifically for your head but you do have to make sure that its specs will allow it to be used with it. They are available on eBay or through electronic supply companies.

 

Just out of curiosity, I am going to try to upload an image here. I just want to give this a try.

 

 

Best<div></div>

[dennis_ng]

Well 7 years later same problem

 

I plug the thermo cord to the wall and the other plug to a device called "aristo solid state contractor model 1200" which has

1 plug for a light source up to 1200w and 2 other cables. One cable to aline(black) also to the wall. The other gray line to

the timer.

 

It seems to work. Hope it is right.