Print consistency: mains voltage

[Jim Jones]

Like Mike, I use an ancient ferroresonant voltage regulator. Mine is a Raytheon brand, although Sola regulators are more commonly encountered. They are simple and durable. Modern electronic regulators should be more efficient and quiet.

[silveror0]

Interesting discussion. Does anyone know the best location in the system to place the voltage regulator, i.e., between the AC outlet and the timer vs between the timer and lamphouse? Does it really matter? I bought a used Sola with the proper KVA rating ($80) years ago and plugged it directly into the AC outlet, and it didn't last long before crapping out. Don't know if it was running continuously (no noise ever) and used it up, or if it was well used and ready to quit anyway. I've been using a Time-O-Lite timer at that time and still do, but since building/installing an LED lamphouse for my 5x7 Omega I'm planning to use an electronic GraLab timer w/ footswitch (currently used for other purposes) for greater accuracy.

[polyglot]

You can get this one which is not exactly cheap but reasonable in price.
http://www.automationdirect.com/adc/.../PSM24-REM360S

That's pretty much exactly the sort of thing I was considering, except more the brick form-factor than DIN-rail.

In terms of my current transformer, it could well be a ferroresonant as it has two separate secondaries and I think there's a big capacitor in there. Ferroresonance didn't occur to me at the time (I had it open to trace the schematic for the back plug) so now I'm going to have to check.

adelorenzo: they are transformers. They give you isolation from the main supply and step the voltage down from 115 or 240V to (probably) 24V. They may or may not be ferroresonant. You must use them for their voltage-converting role if nothing else.

silveror0: shouldn't matter for regulation purposes. If it's always on (timer after stabiliser) it will use more power, but that's not an uncommon arrangement.

[Sirius Glass]

My enlarger has a voltage regulator and I have never had that problem.

[pjbc]

Doesn't a computer UPS work as voltage regulator/stabilizer?

[Sirius Glass]

Doesn't a computer UPS work as voltage regulator/stabilizer?

No, it is a backup power supply, not a voltage regulator. It will do nothing in a brown out until and unless the voltage drops below a setting.

[cliveh]

I did some prints last night and then again tonight; identical exposures (according to my electronic timer) and brand new developer in each case.

The densities are different. Our mains voltage varies a bit and I have a traditional lightbulb enlarger, so my suspicion is that that has caused the exposure error of about 0.15 stops - quite visible in the final print.

So I can see that having some sort of brightness-feedback system as is required for (highly variable) cold heads might also be of some value when printing with tungsten.

This has probably nothing to do with your equipment, but a difference in developer temperature and ambient temperature difference.

[ic-racer]

I did some prints last night and then again tonight; identical exposures (according to my electronic timer) and brand new developer in each case.

The densities are different. Our mains voltage varies a bit and I have a traditional lightbulb enlarger, so my suspicion is that that has caused the exposure error of about 0.15 stops - quite visible in the final print.

So I can see that having some sort of brightness-feedback system as is required for (highly variable) cold heads might also be of some value when printing with tungsten.

Variacs are pretty inexpensive. You already own a voltmeter. If it is day-to-day variation in the line voltage then just set your voltage with the variac at the beginning of each printing session. As you probably know, the automatic regulated power supplies that will keep the voltage fixed will be pretty expensive.

[polyglot]

This has probably nothing to do with your equipment, but a difference in developer temperature and ambient temperature difference.

I process prints in a Jobo at 24C. If it's consistent enough for E6, it's more than consistent enough for B&W prints that are developed to completion. And in fact the ambient temp was higher on the day with lower density.

Variacs are pretty inexpensive. You already own a voltmeter. If it is day-to-day variation in the line voltage then just set your voltage with the variac at the beginning of each printing session. As you probably know, the automatic regulated power supplies that will keep the voltage fixed will be pretty expensive.

A variac actually turns out to be $$$ in AU, even compared to a switchmode supply


One nice thing to discover from all this though is that a normal photographic incident-lightmeter serves (with the dome removed and the photodiode exposed) as a perfectly good enlarging meter. You just need to ignore the absolute readings and work in differences of stops. I reckon I'm going to have to write down a couple of tables of print zones vs meter readings, which should save me a shirtload of time on test strips. Certainly saved me a bunch of time the other night when printing one image at three different sizes.

[Jim Jones]

Interesting discussion. Does anyone know the best location in the system to place the voltage regulator, i.e., between the AC outlet and the timer vs between the timer and lamphouse? Does it really matter? . . .

My regulator is between the timer and the enlarger to reduce power consumption and that annoying hum.