Aristo cold head

Nicholas O. Lindan wrote:
"john" wrote

Aristo also has a device to allow the use of digital timers [with a
T-12]. Is it necessary with the F-Stop timer?

It shouldn't be.

[snip]
I don't know the inductive characteristics of the T-12 and don't have any
experience with this unit. My guess is it will work, but there is a
chance the external 'solid state contactor' may be needed. In any case,
plugging the head in and seeing if it works will cause no damage to the
timer.

I do not know the inductive characteristics of cold light heads either.
If the load on the step up transformer were resistive, the load would be
reflected back through the transformer and place a resistive load on the
timer and the power company. Now a gas discharge tube is not resistive, but
it probably has a resistor in series with it to reduce the peak current
through the tube, so it may be more resistive than the tube itself.

--
.~. Jean-David Beyer Registered Linux User 85642.
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/( )\ Shrewsbury, New Jersey http://counter.li.org
^^-^^ 20:50:01 up 10 days, 13:22, 3 users, load average: 4.61, 4.50, 4.33

"john" wrote in message
m...
"Richard Knoppow" wrote in
message
m...
( saltsman enlarger, Aristo T12 cold head)

If you have the original shutter it will work well
with the cold light head, they want to run continuously.
[... snip excellent information]

No shutter came with it, but I have a 110V shutter from
old long-roll school camera that will fit in front of
either lens.

Does your Saltzman have one or two support rods for
the bellows?

It has two, Richard, with the worm-drive rod between them,
driven by a sintered bronze gear. I can make pictures to
put online if you wish.

John

You have the more elabrorate version of the enlarger.
The cheaper (but not cheap) one had the single support rod.
This type was also used for aerial mapping and similar
applicatons. It should have a focusing wheel to drive the
bellows. Some of the larger models also had a small
handwheel to operate the stop ring on the lens.
Photographs would be interesting, I suspect many have
never seen a Saltzman. I have an ancient Saltzman catalogue
somewhere. I really must search it out.


--
---
Richard Knoppow
Los Angeles, CA, USA

"Richard Knoppow" wrote in message
m...

"john" wrote in message
Does your Saltzman have one or two support rods for the bellows?

It has two, Richard, with the worm-drive rod between them, driven by a
sintered bronze gear. I can make pictures to put online if you wish.

John

You have the more elabrorate version of the enlarger. The cheaper (but
not cheap) one had the single support rod. This type was also used for
aerial mapping and similar applicatons. It should have a focusing wheel to
drive the bellows. Some of the larger models also had a small handwheel to
operate the stop ring on the lens.

This one has two hand-wheels below the baseboard. One raises and lowers the
head assembly using two chains that run up and down the inside of the main
column, and the other wheel moves the bellows (focus). It has another pair
of smaller hand-wheels on the horizontal supports (of the triangulated head
support) to move the head to and fro. Today I am measuring those parts to
see if I can add a belt or lightweight chain drive from one of the smaller
wheels to drive the other: this would allow the operator to move to-fro
using one wheel and obviate having the enlarger sit 30 inches from the wall.
(Or a person could just disengage the worm-screw and push/pull by hand.)

I would very much like to work out a remove F-stop control. Will think about
it.

There are mounts for other things such as the red filter rod which are empty
right now. And an odd part that I cannot figure out. If I can get a digital
snapshooter I will make some pictures and post the address.

"Jean-David Beyer" wrote

Now a gas discharge tube is not resistive

A gas discharge tube has a negative resistance: If you increase
the current it will lower the tube voltage. Modeling the lamp
as a constant voltage, though, is good enough for most circuit
analysis - the result is like driving current backwards through
a battery, the voltage on the 'battery' is the arc voltage.
In this model the lamp has zero resistance.

Since the lamp is pretty much a short circuit - zero resistance
- there needs to be a 'ballast' in series with the lamp. The
ballast can be a resistor, capacitor or inductor. The ballast
impedance (the general term for something that opposes current)
controls the lamp current.

In almost all equipment the ballast is either inductive or
capacitive - called a reactive ballast. Resistor ballasts are
sometimes found in very old equipment.

A reactive ballast will draw current 90 degrees out of phase
with the power line. The power that it blocks is stored in
either a magnetic field (inductor) or an electric field (capacitor)
and given back to the power line in the next half cycle (a sloppy
explanation, but probably good enough). A resistive ballast
dissipates the power as heat and the power is gone forever.

The reactive ballast causes the system to draw extra current,
though not power. This upsets the power company, means larger
wiring and transformers are needed and raises the electric bill
if your meter charges you for VARs. Large lamp power supplies
include power-factor correction by adding compensating inductance
to a capacitive ballast power supply or compensating capacitance to
an inductive ballast power supply. This makes the lamp system
draw the least amount of current and look like a resistor to the
power line. http://en.wikipedia.org/wiki/Power_factor

Putting a capacitor of the right value at the input to an Aristo
lamp will make the system look like a regular old light bulb and
there will be no inductive kick when it is turned off. However,
because of the capacitor there will now be a current surge when the
lamp is turned on. "Pay now or pay later."

These problems can be eliminated by connecting the power when the
AC voltage is zero and disconnecting the power when the AC current
is zero. This is what Aristo's 'solid state contactor' achieves.

--
Nicholas O. Lindan, Cleveland, Ohio
Darkroom Automation: F-Stop Timers, Enlarging Meters
http://www.darkroomautomation.com/index2.htm
n o lindan at ix dot netcom dot com

"john" wrote in message
m...

"Richard Knoppow" wrote in
message
m...

"john" wrote in message
Does your Saltzman have one or two support rods for
the bellows?

It has two, Richard, with the worm-drive rod between
them, driven by a sintered bronze gear. I can make
pictures to put online if you wish.

John

You have the more elabrorate version of the enlarger.
The cheaper (but not cheap) one had the single support
rod. This type was also used for aerial mapping and
similar applicatons. It should have a focusing wheel to
drive the bellows. Some of the larger models also had a
small handwheel to operate the stop ring on the lens.

This one has two hand-wheels below the baseboard. One
raises and lowers the head assembly using two chains that
run up and down the inside of the main column, and the
other wheel moves the bellows (focus). It has another
pair of smaller hand-wheels on the horizontal supports (of
the triangulated head support) to move the head to and
fro. Today I am measuring those parts to see if I can add
a belt or lightweight chain drive from one of the smaller
wheels to drive the other: this would allow the operator
to move to-fro using one wheel and obviate having the
enlarger sit 30 inches from the wall. (Or a person could
just disengage the worm-screw and push/pull by hand.)

I would very much like to work out a remove F-stop
control. Will think about it.

There are mounts for other things such as the red filter
rod which are empty right now. And an odd part that I
cannot figure out. If I can get a digital snapshooter I
will make some pictures and post the address.

The filter rod was also used to hold the shutter. The
original was a two blade arrangement similar to a Packard
shutter worked by a foot pedal. Not all had the iris control
and I don't know the details of how it was coupled.
One option was a condenser lamphouse with about 14"
condensers and a mirror arrangment for the lamp. These had a
focusing control for the lamp on the housing and its
possible some had a remote handwheel for this also. I wish I
could find my catalogue but it got boxed up. Time for some
garage cleaning I'm afraid.
You probably need a five foot ladder to go along with
the enlarger.
Saltzman also made a very heavy, geared, tilting
baseboard for perspective correction. I've only seen
pictures of these.

--
---
Richard Knoppow
Los Angeles, CA, USA

"Richard Knoppow" wrote in message
m...

The filter rod was also used to hold the shutter.

This one has provisions for two rods, each about 1" from the edge of the
lens, extending down as far as one wants to make a rod. I'm a little
concerned that shutter movement will cause vibration shake, however subtle,
so I might mount the shutter from a sliding arrangement on the mail column,
which just cannot possibly move. (750 pounds of it). Two more rods can be
added with simple drilling and tapping. So much real-estate on this thing!

You probably need a five foot ladder to go along with the enlarger.

Heh! I have a vision of Watson on the ladder, "Mr. Holmes, is it correct
now, Sir?"

Saltzman also made a very heavy, geared, tilting baseboard for
perspective correction. I've only seen pictures of these.

Over the years of building things like Harleys
http://www.digoliardi.net/butcher.jpg , working on tractors, building cars
and rebuilding VWs http://www.digoliardi.net/58.jpg ,
http://www.digoliardi.net/bug_n_brad.jpg has made me comfortable with making
large things. A geared baseboard would be simple. But the demand for such a
thing is a market of One!

Richard, here a just a couple snapshots of two parts of the Saltzman. The
upper section of the snapshot shows the front lower with the large two
hand-wheels. Left is focus and right raises and lowers the whole head.

The close-up is the rear of one horizontal bar of the head section. Turning
the wheel moves the head forward and back. The other is exactly the same.
They were missing the gears, retainers, and spacers - everything but the
wheels. I haven't got the connecting chain yet (#40 chain, I think
ten-pitch). Got the hubs, spacers and gears at the tractor parts shop today.

It's hard to shoot snapshots in the shed. This was done with the doors open
to the 6pm MinneSnowta May sun.

Duh! I forgot the link: http://www.digoliardi.net/salt1.jpg

On 5/18/2008 5:58 PM john spake thus:

Duh! I forgot the link: http://www.digoliardi.net/salt1.jpg

OMG, I'm drooling; a real piece of Industrial Equipment. Should be a
centerfold in some magazine. Great stuff!

Good luck, and please keep us informed of future developments.


--
The best argument against democracy is a five-minute
conversation with the average voter.

- Attributed to Winston Churchill

"David Nebenzahl" wrote in message
s.com...
On 5/18/2008 5:58 PM john spake thus:

Duh! I forgot the link: http://www.digoliardi.net/salt1.jpg

OMG, I'm drooling; a real piece of Industrial Equipment. Should be a
centerfold in some magazine. Great stuff!

One of my brothers, an expert in ancient warfare, alikened it to a seige
machine. So if it doesn't work out...