Zone VI Type II Cold Head malfunction...
... or perhaps just user error!
Our photo department was given a generous donation in December which included the titular enlarger. Overall it was in good shape, but this is my first experience with (what I believe to be) a cold head, or Zone VI, and there is no manual, nor can I find one online (but would appreciate a link!). So please excuse any idiotic things I may type, as Saunders and Beseler have been my equipment until this point.
Problem: When the head is plugged in, the only time it emits any sort of light at all is a stuttering green/blue flash when it is switched off. When the head is not mounted and you tilt it, there is a very sad (and very expensive-sounding) metallic rattle. However, the fact that it is emitting at least some light is promising to my beginner's mind.
Initially I was thinking, well, I'll just re-lamp it, but... well. I suppose the whole "should only be opened by trained technician" sticker dissuaded me.
I checked out Calumet and saw a photo of a cold light head and there was this little digital jobbie that plugs into the phone cord that sticks out of the head. I have not located this item and wonder if that could be the problem?
Thank you for your time,
I'll take a shot at this. From your description of blue/green light, I take it this is a Variable Contrast head with both blue and green lamps. Do you have the control panel? This plugs into the head and controls the amount of blue and/or green light that the head emits. It sounds as though this part might be missing or at least not plugged in. The controller is a small black panel about 5x7 inches. It has 3 dials, soft, hard and I believe the third dial is marked intensity.
I hope this helps,
I believe that you are correct, and the control panel must be what I so eloquently described as a "digital jobbie." I will take an intense look in all of the boxes on Thursday and will see what I can come up with. Hopefully locating it and plugging it in will help out. Thank you so much for your reply!
Here you can see mine in my darkroom.
I hope it will help.
There should be 2 places to plug that head in. One is 120 volts for the heater, and stays plugged in always. The other is 120 volts and is usually switched on by your timer.
Originally Posted by jeannette
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The Zone VI VC cold light is not a single item but rather a series of modifications made to solve notoriously unstable performance. I owned one of the earlier models and ended up in a rather heated debate with Calumet in which they finally refunded my money.
My advice is to talk to Calumet and determine what vintage you are dealing with. Ask the Technician if this model is one where exposure-to exposure variance was a problem. (Mine varied by 25 to 40%!) If so, do not pour money into it. It will drive you crazy.
If the Technician clams they had no problems, you are talking to someone who doesn't know the history.
Jeanette: I found the instructions for my VC head, here are a few of the pertinent details (paraphrased):
(1) If you look at the head from the front (where the power switch is located) there are three sockets on the top, plus a phone-like cable exiting the head. The rearmost socket on the right is the power inlet, the similar socket to the left of it is the timer inlet (so that cable connects to the receptacle on your timer marked "lamp" or "enlarger"). The "telephone" type cord exiting from the head connects to the "telephone" type jack on the back of the control box (that digital thingie you are looking for, it has three dials and a "focus/print" switch). The last connection on top of the head is for a ZoneVi Compensating Enlarging Timer, Tik-Tok, or other compensating type timer. I don't use it, since I don't have any of those specialized timers.
(2) The head has both green and blue (soft & hard) tubes, controlled by the box. If you set the hard and soft dials on "E" you have roughly grade 2. Set the intensity at max, 10. You vary contrast by dialing up or down the soft or hard dials. If you hunt on APUG, another user posted the link for a table of contrast settings, which is quite useful.
(3) MOST CRITICAL: the head has a monitoring circuit to detect when light output from both tubes is stable, and the green light on the front of the head must be on throughout exposure to ensure stability. Basically this relates to the temperature of the tubes. My own practice is to keep the head on "focus" (i.e. tubes on, max intensity) most of the time, so that when I switch to "print" everything is stable (so when my print is in the fixer, I flip the enlarger to "focus"; then when I evaluate the print, the enlarger is ready for the next iteration). The alternative is to make a "blank exposure" (no paper in the easel) before each real exposure, checking that the green light stays on; if it doesn't, another blank exposure, etc.
Incidentally, although I don't feel like copying it in its entirety, there is an explanation of the closed-loop stabilizing circuitry. Essentially there is a shielded sensor for each tube; when it detects a change in intensity it adjusts the voltage to the tube. However, when the tubes are "off" they cool down, and they must be within a certain temperature range for the stabilizing circuit to work. That's why you need the blank exposure or "focus" time to keep everything in the temp range where the stabilizer works. I've used my ZoneVI head for many years, and as long as I make sure the green ready light is on throughout the exposure, I get very repeatable results.
Sorry for the length of this post, hope it is useful.
I have a type II enlarger that has served me very well. From your description, it sounds like you may not have everything connected properly. I have the instruction manual somewhere - it is not that long. I can scan and email to you if you would like.
Originally Posted by jeannette
The phone chord is for a photocell installed in the light head for the purpose of sensing the light intensity in order for the timer to adjust the time intervals for exposure compensation, i.e, one second of time (realtime) will change to something other one second, accordingly, as the lamp brightness fluctuates giving you consistent (constant) exposure for printing multiple prints from the same negative. I've been using a none VC (Zone VI) head for years (early model I presume) - works great!
"Pictures are not incidental frills to a text; they are essences of our distinctive way of knowing." Stephen J. Gould
The head uses a DIN cord to connect to the photocell. The phone cord is to connect the VC controller.