Omega Timer With Aristo Cold Light?

[tgtaylor]

Hi all,

I just puchased a used Beseler MXT enlarger that came with an Aristo D2 Cold light head. I have never used a cold light head before and I am wondering if my Omega ET-500 timer will handle the inductive loads that a cold light source gives. Your insight on this is greatly appreciated.

Thomas

[neil poulsen]

It's hard to get consistent results using these heads. If you get one, get one with a heater. It'll have two cords for plugging it in. (A thicker one for the heater and a thinner one for the light source.)

My suggestion would be to get a compensating timer like the Metrolux. But, I don't really know if they're still made? There are others. The Zone VI would be an option, except that it's no longer possible to get the separate sensors. (On perpetual backorder.)

These timers adjust for the high variation that cold light sources exhibit by varying the "speed" of time as the light varies in brightness.

Otherwise, one can help smooth out the variability by leaving the head on prior to printing to make sure the heater is at its peak, and waiting an interval of time between exposures, etc.

[Merg Ross]

Thomas, I am uncertain of the answer re your specific timer. However, along with my Aristo V-54 Cold Light came the following warning from Aristo: "If you are using a digital or solid state timer, check the manufacturers specifications to see if your model is compatible and can handle the inductive load of a cold light head. If you are uncertain, a solid state Contactor model #1200 can be purchased from Aristo which will protect your timer and boost its power handling capabilities to 1200 watts inductive load."

My setup is with the V-54 Cold Light, the Contactor model #1200 and a 545 Gralab timer. It has worked well for the past six years and is very consistent once it heats up. Neil mentioned this above, and I find the V-54 to be more consistent than the earlier Aristo Cold Light. Assuming that you have the V-54, you may want to add a solid state dimmer made by Aristo.

Hope this helps. Aristo used to be very helpful answering questions, and probably still are, assuming they are in business.

[tgtaylor]

Hi Neil,

Thanks for the reply.

The head has the two cords that you mentioned. The burning issue right now is whether or not the Omega/LPL ET-500 timer will safely work with the inductive load of the cold light source and, if not, would attahing a voltage regulator or some other device solve the problem. I wouldn't want to buy another timer just to use with the Aristo.

I E-mailed Omega Satter customer support this afternoon. Hope they respond.

Thomas

[tgtaylor]

Hi Merg,

Thanks for that reply!

The timer manual sets both enlarger lamp and safelight capacity at "Under 500W" each. Do you know that the max output of the Aristo is?

Thomas

[tgtaylor]

On the back of the Aristo head is states the output as 70 watts. Since 70 watts is well under the timers 500 watt capacity for the enlarger, it looks like there should be no problem. But I'm not an electrical engineer (I slept during that class) and I don't know if the head could induce a load in the timer that would exceed the 500 watt limit.

[Peter Langham]

Thomas,

Years ago, I had a similiar set up. I don't remeber the timer model, but it was an Omega. It would not handle the load (it would shut off or not turn on or something). I am no kind of engineer, but I told my brother in law, who is. He disappeared and returned with something I think he called a "snubber" or something like that. Anyway, it solved the problem, and my set up worked fine. It is probably something like the contractor mentioned above. I did use a Zone VI stabilizer for more consistent results.


Peter

[Donald Miller]

I had this setup at one time. I built my own contactor loop to handle the load. All that is needed is a DPST NO 10 amp contactor with 120 volt coil...let the timer enlarger lamp outputs supply the coil voltage and have a live 120 volt sitting on each of the double poles of the contactor. Probably a lot less expensive than Aristo's contactor. Any HVAC supply house would have the contactor that you need.

[Merg Ross]

Hi Thomas-

It sounds like you have the D2 with a V54 lamp which Aristo rates at 70 watts. The high intensity lamp is rated at 110 watts and is very bright. Hence, my mention of a dimmer, but you should be fine without one. You have some good advice above re the contactor; for the record, I paid around $100 for mine in 2002.

Hope you enjoy printing with the cold light. Always a controversial subject, but after years of condenser printing I made the switch and prefer the look of the cold light prints. However, it does take a different type of negative from those intended for condenser printing.

[tgtaylor]

Thanks everyone for the replies. I sent an E-mail to Aristo and to Omega-Sater and will post their response if received. Hope I dont need the contractor.

Yes, it is the V54 model. Has a little sticker on the top with V54 written on it.

This will be the first time printing with a cold light. From what I've read so far, you are supposed to position the negative as close to the cold light source as possible. so I guess that means to close the head down on the negative carrier regardless of the film format.

I bought and picked-up the enlarger yesterday afternoon. It is now set-up in my bathroom and looks great. I ordered the instruction manual yesterday so I can properly align it. Using a torpedo level, the stand and baseboard is level. Using a flat piece of glass in the carrier, the negative carrier looks like it could be tweaked a tiny bit but I can't see where you would do that. Haven't figured out how to check the lens stage yet.

[ic-racer]

These coldlights have a big transformer that takes 120V up to almost 500v. I suspect these transformers come from the 'neon light' industry. When you first turn it on, there is somewhat of a power surge, and I believe this is what they are referring to with the 'inductive load.'

There was so much extra room in my Aristo power supply case that I was able to put a big relay in there. Now my timer just powers the coil of the relay and I don't have to worry about potential damage to my timer. I added a 3 way switch so I could bypass the relay if I wanted.

http://www.largeformatphotography.info/forum/showpost.php?p=318145&postcount=19
http://www.largeformatphotography.info/forum/showpost.php?p=318146&postcount=20

With the heater on, I measured pretty constant temperatures. I did not notice any change in temperature or print quality over the course of a printing session. http://www.largeformatphotography.info/forum/showpost.php?p=320895&postcount=43

Here is an example of the heater and thermostat, if you have not opened yours up to check it out : http://www.largeformatphotography.info/forum/attachment.php?attachmentid=10082&d=1202923345

Yes, get the diffuser as close to the negative as possible, otherwise it will form a hotspot in the middle. I went to a lot of trouble to make mine as close as I could get it. http://www.largeformatphotography.info/forum/showpost.php?p=319616&postcount=29

[Claude Sapp]

I had this setup at one time. I built my own contactor loop to handle the load. All that is needed is a DPST NO 10 amp contactor with 120 volt coil...let the timer enlarger lamp outputs supply the coil voltage and have a live 120 volt sitting on each of the double poles of the contactor. Probably a lot less expensive than Aristo's contactor. Any HVAC supply house would have the contactor that you need.


I have always wondered why my Omega timer never worked quite right with my Aristo heads. It sort of works, but will not shut off completely after the timer has shut off, the coldlight still burns very dimly, it does not shut off completely.

Donald, is the contactor a plug in affair, or does it require wiring?

[tgtaylor]

Hi IC-Racer,

Believe it or not, but not more than 30 seconds before I was notified of your post I bought an ARISTO SOLID STATE CONTACTOR MODEL 1200 advertised as brand new off ebay for $45 "buy it now" (+$10.00 and $3.71 tax) or $58.71 total. The Calumet website list it for $99 + shipping and tax so if it truly is "brand new" I got it for half price and about $5.00 more than getting the devise from an electrical/HVAC source as recommended by Don in an earlier post. (Thanks Don, I was seriously considering that until I just happened upon the ebay post a few minutes ago.)

I never received a reply to my email to either Aristo or Omega Satter and Wednesday I called Omega and spoke with their tech Greg who said that he didn't know whether the ET-500 would take the inductive load (i.e., change of polarity) of the Aristo and was sending off for the schematic and would let me know NLT tomorrow (Monday). Naturally, now that I bought the Contactor, he'll call tomorrow and say that Omega built the ET-500 specifically to handle inductive loads!

The issue now is whether to invest in the (Horowitz) stablizer as recommended by Ansel Adams in "The Print" which I am now reading. Is the stablizer needed with the new V54 head?

Thomas

[Merg Ross]

Thomas, the contactor should do the trick for you, good price. My experience is that after about a fifteen minute warm up time, the V54 stays consistent throughout the printing session. I usually print for six or eight hours at a time and have not had a problem with consistency. Once you get set up, give it a try, you may find the same to be true.

[tgtaylor]

That's good news Merg!! Thanks.

[ic-racer]

The issue now is whether to invest in the (Horowitz) stablizer as recommended by Ansel Adams in "The Print" which I am now reading. Is the stablizer needed with the new V54 head?

Thomas

I think that may depend on where you live. I make an analogy to a water filter. Where I live, the faucet water has never been a problem, and a darkroom water filter is near the bottom of my to-do list. Likewise, my line voltage seems pretty constant.

I guess you could monitor your line voltage over a few weeks or months and see. Maybe someone with one of those coldlight voltage stabilizers can comment on its value.

[Eric Woodbury]

I have some data of v54 light output vs time with heater on and with varying amounts of light-on time. It is fairly consistent, but if you were printing high key images with extreme sensitivity to threshold values, I suspect you'd still have problems with runs of several prints.

I don't have light output vs input voltage. My voltage is a consistent 117VAC, but I know that this is not the case for most people.

I will try to find the data and get them posted soon.

[Eric Woodbury]

Here are the data. The temp is a thermometer in the light chamber and the brightness units are just 'units' from a MetroLux. I hope the columns work out here.

You can see that if your on/off ratio is very consistent, then after an hour or so, exposures may be consistent w/in 1 or 2 %. This is usually fine, but as I mentioned, highkey prints with sensitive high value at threshold will trip you up. Threshold values are so exaggerated by exposure variations of the smallest magnitude.

November 20, 2006
V54 coldlight test
Light on continuously from 0 to 25 min, then off and only on for measurement lasting 30 sec.
Time Temp, F Brightness
0, 70, 45
0.5, 70, 50
1, 70, 59
1.5, 72, 69
2, 70, 77
2.5, 75, 82
3, 77, 91
3.5, 79, 99
4, 81, 106
4.5, 82, 111
5, 86, 117
5.5, 88, 122
6, 90, 125
6.5, 91, 129
7, 93, 131
7.5, 94, 132
8, 98, 133
8.5, 100, 133
9, 101, 133
9.5, 103, 133
10, 105, 132
15, 111, 127
20, 118, 124
25, 125, 121
40, 107, 117
50, 104, 115
60, 103, 115
70, 102, 116
80, 101, 118
90, 101, 119

[tgtaylor]

Hi all,

I got a voice mail from Greg at Omega/Satter this afternoon and he said that he heard back from Omega who said that the ET-500 timer will work with cold light sources and gave him no further elaboration. About the same time I got an E-mail from the guy on E-bay with the tracking number of the Contractor. So I'm going to connect the Contactor to the timer anyway. If it works for Merg, it (better!) work for me.

Now that that's taken care of, time to get down to business. I saw several great B&W shots yesterday but because of the time and lighting couldn't take them. But this weekend...

Thanks all for the help on this. I owe you one (or two)!

Thomas

[Merg Ross]

Thomas, I bet the contactor will work just fine.

By the way, for you and others in the Bay Area looking for photo equipment, a good source is the Hayward Camera Show sponsored by the East Bay Camera Collective. The next one is this Sunday (3/30) from 9:30 to 3:00 at Centennial Hall located at 22292 Foothill Blvd. I have been there a couple of times and there is always a good variety of equipment.