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Aristo cold head



 
 
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  #1  
Old May 17th 08, 03:17 AM posted to rec.photo.darkroom
john
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Posts: 22
Default Aristo cold head

I know nothing about cold heads (except being bald in a Minnesota Winter).

Need something for the 8x10 Saltzman enlarger. On EvilBay there is an Aristo
T12.

Seller wants $575 BIN. Here is the ad copy:

"This is the top-of-the-line 8x10 enlarger light source. Aristo T12 High
Intensity Light Head is a two part unit -lamp housing and power pack- which
contains a three prong thermo cord which operates the thermostatically
controlled heater. This is plugged into any available 115V outlet. The lamp
housing is 11-7/8" x 11-7/8" x 6-3/4" high."

Is that everything I need for the light source? Is there a particular
"gotcha" to beware of?

I truly appreciate any help on this you all can offer.

John


  #2  
Old May 17th 08, 06:07 AM posted to rec.photo.darkroom
Ken Nadvornick
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Posts: 240
Default Aristo cold head

"john" wrote:

I know nothing about cold heads (except being bald in a Minnesota
Winter).

Need something for the 8x10 Saltzman enlarger. On EvilBay there
is an Aristo T12.

Seller wants $575 BIN. Here is the ad copy:

"This is the top-of-the-line 8x10 enlarger light source. Aristo T12
High Intensity Light Head is a two part unit -lamp housing and power
pack- which contains a three prong thermo cord which operates the
thermostatically controlled heater. This is plugged into any available
115V outlet. The lamp housing is 11-7/8" x 11-7/8" x 6-3/4" high."

Is that everything I need for the light source? Is there a particular
"gotcha" to beware of?

I truly appreciate any help on this you all can offer.


Hi John,

I don't have any personal experience with an Aristo T12, but perhaps Aristo's
own product page for this unit will help you in determining if this unit is
right for you...

http://www.aristogrid.com/t12.htm

Ken


  #3  
Old May 17th 08, 01:21 PM posted to rec.photo.darkroom
john
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Posts: 22
Default Aristo cold head

"Ken Nadvornick" wrote in message
. ..


I don't have any personal experience with an Aristo T12, but perhaps
Aristo's
own product page for this unit will help you in determining if this unit
is
right for you...

http://www.aristogrid.com/t12.htm


OMG! I broke my own rule! I did not look it up. See, I thought it was an
obsolete part.
Thanks for the nudge, Ken!

John


  #4  
Old May 17th 08, 01:36 PM posted to rec.photo.darkroom
Jean-David Beyer
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Posts: 247
Default Aristo cold head

Nicholas O. Lindan wrote:
"john" wrote

On EvilBay there is an Aristo T12. .... Is there a particular "gotcha" to
beware of?


You may need to stick to graded paper - it looks like the
original 'actinic' tube. I had a head with this tube on
a D-series Omega and it only wanted to produce grade 4+
VC prints. Some people say they can get by throwing
a lot of yellow filtration into the system.

Aristo make a lot of different color tubes in their heads, each with a
different characteristic curve. Some will work pretty well with about Y40 or
so yellow filter in addition to your regular vc filters. Others will not.

You might find the following curves helpful:

http://www.aristogrid.com/spd.htm

They also make heads with a blue and a green tube so you can use VC paper
more easily. I have an Aristo head (D2HI) that came with either a W45 or a
V54 tube in it and that worked OK with a yellow filter, although I used
graded paper at the time, so it did not matter much to me.

--
.~. Jean-David Beyer Registered Linux User 85642.
/V\ PGP-Key: 9A2FC99A Registered Machine 241939.
/( )\ Shrewsbury, New Jersey http://counter.li.org
^^-^^ 08:15:01 up 10 days, 47 min, 3 users, load average: 4.02, 4.06, 4.09
  #5  
Old May 17th 08, 01:37 PM posted to rec.photo.darkroom
john
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Posts: 22
Default Aristo cold head

"Nicholas O. Lindan" wrote in message
m...
"john" wrote

On EvilBay there is an Aristo T12. .... Is there a particular "gotcha" to
beware of?


You may need to stick to graded paper - it looks like the
original 'actinic' tube. I had a head with this tube on
a D-series Omega and it only wanted to produce grade 4+
VC prints. Some people say they can get by throwing
a lot of yellow filtration into the system.


That is a critical issue. Thank you! Aristo also has a device to allow the
use of digital timers. Is it necessary with the F-Stop timer?


  #6  
Old May 17th 08, 02:12 PM posted to rec.photo.darkroom
Nicholas O. Lindan
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Posts: 1,227
Default Aristo cold head

"john" wrote

On EvilBay there is an Aristo T12. .... Is there a particular "gotcha" to
beware of?


You may need to stick to graded paper - it looks like the
original 'actinic' tube. I had a head with this tube on
a D-series Omega and it only wanted to produce grade 4+
VC prints. Some people say they can get by throwing
a lot of yellow filtration into the system.

--
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


  #7  
Old May 17th 08, 03:21 PM posted to rec.photo.darkroom
Nicholas O. Lindan
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Posts: 1,227
Default Aristo cold head

"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.

There are two technologies timers use to control
the lamp: electro-mechanical relays and solid-state
silicon controlled rectifiers (SCRs).

Some electronic timers with relays get upset by the
electrical interference generated when the contacts
open with an inductive load. Current through an
inductor wants to keep flowing and can't be stopped
instantly. When relay contacts open the current
creates a small arc across the contacts. A 'snubber
circuit' across the contacts provides a path for this
current and limits the arc. The f-Stop Timer uses
a snubbed relay rated at 12 amps.

Since SCRs only turn off when the current goes
to zero they have no trouble turning off inductive
loads. OTOH, they can have problems with incandescent
lamps. When a light bulb fails it often creates
a dead short - the bright flash/pop - and the current
through the short can destroy an SCR that is not
adequately protected. They are also prey to
high-voltage surges on the power lines. Snubber
circuits are used with SCR's, but this time to
absorb power line spikes when the SCR is off.

Timers that are properly designed and used will
work without problems using either relays or
SCRs.

High-power loads connected to a timer can require
an external contactor to handle the current. Regular
Aristo 4x5 heads are no problem for most any timer,
including the Darkroom Automation f-Stop Timer.

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.

--
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


  #8  
Old May 17th 08, 07:36 PM posted to rec.photo.darkroom
john
external usenet poster
 
Posts: 22
Default Aristo cold head


"Nicholas O. Lindan" wrote in message
m...
"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?


[... snip good article ...]
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.


Very good to know. Thank you.

So now I know the light source is clearly feasible. I just have to rip this
check out of my tight fist and do it.


  #9  
Old May 17th 08, 10:44 PM posted to rec.photo.darkroom
Richard Knoppow
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Posts: 751
Default Aristo cold head


"john" wrote in message
m...
I know nothing about cold heads (except being bald in a
Minnesota Winter).

Need something for the 8x10 Saltzman enlarger. On EvilBay
there is an Aristo T12.

Seller wants $575 BIN. Here is the ad copy:

"This is the top-of-the-line 8x10 enlarger light source.
Aristo T12 High Intensity Light Head is a two part
unit -lamp housing and power pack- which contains a three
prong thermo cord which operates the thermostatically
controlled heater. This is plugged into any available 115V
outlet. The lamp housing is 11-7/8" x 11-7/8" x 6-3/4"
high."

Is that everything I need for the light source? Is there a
particular "gotcha" to beware of?

I truly appreciate any help on this you all can offer.

John

Others have answered your questions but contratulations
on having this monster, an absolutely superb chunk of
machinery.
If you have the original shutter it will work well with
the cold light head, they want to run continuously. The
Arista has a heater in it to make the output more uniform
when its used intermittantly but all gaseous discharge lamps
increase output as they get hotter and most like to work on
a continuous basis. The Saltzman shutter was made to work
with the original mercury vapour lamp house which _had_ to
run continuously. Saltzman had other lamphouses available
but the Cooper-Hewitt tube type was the most common.
Arista makes lamps which are compatible with variable
contrast paper and can be refitted to older lamphouses.
Does your Saltzman have one or two support rods for the
bellows?


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



  #10  
Old May 17th 08, 11:31 PM posted to rec.photo.darkroom
john
external usenet poster
 
Posts: 22
Default Aristo cold head

"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




 




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