Enlarger electronics

[swmcl]

Hi,

I wonder if some could describe the various electronic bits 'n' bobs on enlargers please?

For example, I see the term 'stabiliser' and wonder what it does. I wonder also whether enlargers have varying power sources to turn the lamp up and down, whether they have a warm-up mode etc. I realise some will and some wont, that's OK.

If an explanation as to the benefits of the technology might also be helpful. Might there be some of the gagetry that is dubiously 'helpful' and some which is an absolute necessity?

Does anyone know whether some are DC and some AC??

No need to describe your colour spectrometer and its associated control circuitry ... we can leave that one out!

Cheers,

Steve

[Jim Jones]

A stabilizer provides consistent output voltage over a range of input voltage. With reliable electric power providers they aren't necessary, but may be worthwhile to some very demanding darkroom workers.

I've never seen an enlarger with a built-in electrical control to vary the intensity of the enlarging lamp, but have occasionally used an external variable transformer for that purpose. It does permit composing and focusing at reduced voltage for longer lamp life.

Most simple enlargers could be operated with a DC lamp if a lamp with appropriate physical characteristics can be found. The frosting in enlarger lamps is very uniform while the frosting in most household lamps isn't ideal for enlargers. Most DC lamps have no frosting at all, which would make them difficult to use in enlargers.

[Steve Goldstein]

Different light sources respond differently to voltage variations and to time. An incandescent bulb will have constant light output over normal enlarging times as long as the line voltage is constant, but it's slightly sensitive to variations in the household 120V (or 220V or 240V, whichever you use). A constant-voltage transformer can help against this. So can a DC supply, but you need to be careful how you turn it on - if the supply is always on and you just close a switch to the bulb you're likely to shorten bulb life. I have a small (300VA) CV transformer to use when I start contact printing the negatives from my to-be-built-someday 7x11 camera on Lodima; I don't know how necessary this really is, but I got the transformer for small money.

A cold light behaves very differently. Its light output is sensitive to bulb temperature so will tend sag with on-time from either long or repeated exposures. These really benefit from either stabilizers (I have the Zone VI, purchased new almost 30 years ago) or compensating timers, both of which monitor the light output and make appropriate adjustments to either the bulb power (stabilizer) or the apparent tick rate (compensating timer). The benefit is most significant if you're trying to make a number of identical prints over a relatively short printing session - prints with the same exposure can differ depending when in the session they were exposed because the bulb will tend to get warmer through the session.

[Bob Salomon]

"I've never seen an enlarger with a built-in electrical control to vary the intensity of the enlarging lamp, but have occasionally used an external variable transformer for that purpose. It does permit composing and focusing at reduced voltage for longer lamp life."

What was that rheostat knob on the Beseler 45 MCRX? I believe also on the CB 7

[Leigh]

Most simple enlargers could be operated with a DC lamp if a lamp with appropriate physical characteristics can be found.
Any lamp rated 110 volts AC can also be operated on 110 volts DC, with exactly the same results and performance.

In fact, this is the definition of the equivalence of AC and DC voltages, specifically...
110 volts AC is the amplitude that will heat a resistor to exactly the same temperature as 110 volts DC.

- Leigh

[Drew Wiley]

Line voltage tends to fluctuate coming in. This can affect the intensity and color temperature of the bulb. Or worse, if you have a fancy modern enlarger with solid
state controls or a built-in timer, it can mess that up. A voltage stabilizer tames this for the correct output, and is therefore considered standard equipment with colorheads. Big enlargers typically run on 220V, but use step-down 115V for the electronic controls. I once was refurbishing one of these monsters, and after I checked my incoming 220 line voltage with a meter, realized it was very stable, and simply gutted all the electronics and installed 220V bulbs. It worked at lot more
reliably after that, and I saved several thousand dollars. But in most neighborhoods, regular 115 line voltage swings a bit too much. Just borrow a high quality multi-meter. Different times of the day can also affect incoming voltage, depending on neighborhood load.

[Tin Can]

Yes, both have a rheostat and I always use it. I never print color so I do lower my voltage to suit my print times. Often to 80 to 90 volts AC.


"I've never seen an enlarger with a built-in electrical control to vary the intensity of the enlarging lamp, but have occasionally used an external variable transformer for that purpose. It does permit composing and focusing at reduced voltage for longer lamp life."

What was that rheostat knob on the Beseler 45 MCRX? I believe also on the CB 7

[Leigh]

Yes, both have a rheostat and I always use it. I never print color so I do lower my voltage to suit my print times. Often to 80 to 90 volts AC.
The spectral characteristics of a lamp depend critically on the applied voltage.
Reducing the voltage will significantly reduce the energy in the shorter wavelengths, particularly blue.

This can make a bit difference with variable-contrast papers. It won't matter much if you're printing graded papers, but it will lengthen the exposure times, just like closing the aperture.

- Leigh

[Tin Can]

Electronics and computers are to be avoided in any enlarger as they are obsolete tech and totally unsupported by any manufacturer. Basic electrical old time enlargers, which is wires and bulbs only, have stood the test of time. As Drew did, it is often best to make it all all as simple as possible, even if a qualified electrician needs to rewire the contraption back to basics.

A sturdy adjustable chassis is more important than keyboards.

[Tin Can]

Aging bulbs also change color temp and I approach each print as individual.




The spectral characteristics of a lamp depend critically on the applied voltage.
Reducing the voltage will significantly reduce the energy in the shorter wavelengths, particularly blue.

This can make a bit difference with variable-contrast papers.
It won't matter much if you're printing graded papers, but it will lengthen the exposure times, just like closing the aperture.

- Leigh

[ic-racer]

Four main types:

Incandescent lamp, usually used in condenser enlarger. Frequently runs off mains voltage.
Quartz Halogen Dichroic lamp, usually used in diffusion enlargers. Frequently runs off voltage lower than mains voltage.
Cold Cathode, usually used in diffusion enlargers. Frequently runs off voltage higher than mains voltage.
LED, usually used in diffusion enlargers. Frequently runs off voltage much lower than mains voltage.


Lamps that run off voltage different than mains voltage need some sort of power supply. Some power supplies are as simple as a transformer, while others are as complicated as the control unit for a horizontal Durst enlarger.

[Jac@stafford.net]

Electronics and computers are to be avoided in any enlarger [...]

I hope you are being facetious. I lived in a rural area where we had serious brown-outs and utter power failures too often. The voltage would drop so low that my PC would go nutz, the enlarger would dim along with every light in the house. Low voltage is the worst thing. At that time I had no UPS.

[Andy Eads]

No matter how good the power is to the house, a hair dryer on the same circuit as the enlarger will drop the voltage substantially. I've had good luck with voltage stabilizing transformers and also uninteruptable power supplies intended for powering your computer during an outage or drop. These work with either incandescent or cold cathode lamps. Using these devices makes printing a greater pleasure as it virtually eliminates exposure variations. I save paper and frustration. I now spend my allowance of frustration on politicians.

[swmcl]

Thank you for your replies.

It looks as though a voltage stabilizer is useful but not necessary. Voltage variations are not so common anymore and hair dryers at 230Vac do not draw the same current as do the 110V couterparts. I may take a reading or two but I've not seen a problem with using them in terms of voltage drops.

The replies have started another query running in my head so I'll start a new thread while I'm at it.

Cheers,