Digital timer for Zone VI Cold Light head?

[Deleted member 19578]

I've read just about every archive post regarding enlarging timers for a cold light head and haven't found a definitive answer...

Can you use a digital timer for the Zone VI Cold Light Head? I've read about problems with inductive loads etc., but haven't found the answer.

I have the following digital timers available:

1) Omega Digital Timer (model 461-016). The nomenclature plate has the maximum enlarger wattage at 650 watts, and the plug specs at 70C watts.

2) Gralab model 900, listed at 1000 watts maximum (gawd how I loathe this timer- you have to push 3 buttons to get it to count!)

I also have the venerable/ubiquitous Time-O-Light model M-72, 750 watts maximum.

Which of the above can be safely used? Or- should I spend the money & buy the Zone VI compensating timer? I have the Zone VI stabilizer for the head, but not the timer.

TIA!

 

[david b]

How about a Gralab 545 ? Max load is 600 Max resistive load is 1200

 

[AllenR]

I've used a Gralab Model 500 digital timer on my zone vi cold light head with stabilizer for more than 20 years. I've never had any problems of any kind.

 

[jeroldharter]

The best timer that you could get is the RH Designs Zonemaster Vario timer which includes a cell that you place in the light source to adjust to the variations in light output of a cold light.

This timer is very expensive and the weak dollar does not help. But, it is one of the most valuable bits in my darkroom. Worth the money.

I have a Gralab 900, Jobo Colorline 5000, Jobo Multitronic, Gralab 300, and a few others sitting in obsolescence because of the RH Designs timer.

 

[Nicholas Lindan]

Can you use a digital timer for the Zone VI Cold Light Head [& stabiliser]....
should I spend the money & buy the Zone VI compensating timer?...

The Zone VI stabilizer will work with any timer. It doesn't have a large inductive 'kick'.

If you have the stabilizer you do not need a compensating timer. The stabilizer has a photocell that monitors the lamp brightness and controls the voltage to give a constant output. A compensating timer does the same thing but it varies the exposure time so the total exposure is constant. Putting both in the system will not improve matters - though they won't 'fight' each other, life can get confusing when you have two pieces of electronics each thinking it is the only one in charge (much like having two bosses).

Compensating timers are a problem with metering probes and enlarging meters. Both the timer and the meter will compensate for any changes in lamp output - as a result any changes are overcompensated. If the lamp output is low the prints will be overexposed and vice versa.

If you use a meter with a compensating timer then you can only make measurements and make prints with the lamp fully warmed up - when the compensating timer has no effect - which begs the question of why use a compensating timer.

A regulated light output is the correct path to take in all cases.

 

[RH Designs]

The best timer that you could get is the RH Designs Zonemaster Vario timer which includes a cell that you place in the light source to adjust to the variations in light output of a cold light.

This timer is very expensive and the weak dollar does not help. But, it is one of the most valuable bits in my darkroom. Worth the money.

I have a Gralab 900, Jobo Colorline 5000, Jobo Multitronic, Gralab 300, and a few others sitting in obsolescence because of the RH Designs timer.

Many thanks for the testimonial Jerold; if I might add a polite correction it's the StopClock Vario . As Nicholas says if your head is stabilised then you don't really need the compensation function so the standard StopClock Professional would do the job and save you a few $$.

 

[Deleted member 19578]

Thanks to everybody for the info! I especially appreciate the input from Nicholas & Richard... It is one of the perks to asking a question on APUG- info from the equipment manufacturer's.

I think I'll hold off on a new timer for the moment & concentrate on making some enlargements. Maybe I should sell some other equipment (ie- a couple too many Graflex's) to pay for a new timer.

John

 

[Marco Buonocore]

I use the darkroom automation f stop timer with a zone vi cold light head, and have had no problems whatsoever. I've been using it for over a year now, so I expect it's fine. I use it together with the zone vi stabilizer.

 

[RJS]

Can you give me information regarding a stabilizer for my cold light? I am using it with an RH Designs timer and I apparently get little or no variation in exposure from one exposure to the next, but a stabilizer would seem a good idea perhaps

 

[Nicholas Lindan]

Can you give me information regarding a stabilizer for my cold light? ... I apparently get little or no variation in exposure from one exposure to the next, but a stabilizer would seem a good idea perhaps

"perhaps" is the key word here.

The saying is "If it isn't broken then you shouldn't fix it, because if you fix it enough times you will break it."

Until you can see variation, produce it on demand, and find it objectionable, don't get a stabilizer. If you can't see variation without one, you won't be able to see variation with one - how will you know it is working and not broken?

If you don't need one then getting one will just add one more thing to go wrong, waste electricity, create pollution and use up money that is better placed in a retirement fund.

It's not like an f-Stop timer; everyone _needs_ an f-Stop timer, as you well know.

 

[ChuckP]

Try exposing 5-10 test prints one after the other. Then process them together. If you can't see any variation then you really don't need a stabilizer.

 

[Nicholas Lindan]

Try exposing 5-10 test prints one after the other. Then process them together. If you can't see any variation then you really don't need a stabilizer.

Very good suggestion ...

If you want to get elaborate:

Make identical small prints

• no negative
• normal enlarger height
• use the highest contrast paper you usually use
• expose for a light-medium grey
• print at the pace of a normal darkroom session, don't speed things up - maybe use a timer
• develop all at once

A stabilizer will also help if you suffer from voltage sags, test by:

• warm the enlarger up fully and leave the enlarger on through the test except for the times you are handling the paper.
• turn off all major appliances, etc.
• make a test print as above
• turn on a reasonable selection of appliances: the air conditioner, drier, refrigerator, house lights ...
• make a second test print
• develop the prints together

The less elaborate approach to the problem is that if you aren't seeing any problems you most likely don't have any.

If you examine anything closely enough you will find imperfections, ones that don't matter and take an awful lot of money and effort to combat. The purpose is to make satisfying photographs and not to run a sensitometry laboratory - I tell myself that all the time, but not often enough if the above lists are any indication.