Photocell for Zone VI compensating enlarging timer

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Deleted member 88956

I've been away for a long time and I'm still looking at about a year before I get to doing darkroom work again, but I can see this issue coming up soon enough.

Having moved from the 110v society to one that runs on 220v, I will likely be acquiring an enlarger within European confines, which is going to get me a light source not completely compatible with my beloved Zone VI compensating enlarging timer. Have looked around and see no particular reference to the photocell that was installed in Zone VI cold light heads and was also then available as part (called Zone VI L 702 photocell). To get the most out of this timer, I am looking for that photocell so I can install it inside the light source(s) I'll end up getting.

Is there anyone who can help locating the cell itself or at least the specs (these parts are widely available, but I'm guessing it needs to match the original specs to work properly with the timer).

I can still use a US source for such, although I'm sure I can locate it on this side as well, just need to know what to look for. Thanks.
 
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E. von Hoegh

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You can also get a transformer which steps down 220 to 120, and will allow you to use your familiar equipment.
 
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Deleted member 88956

No, that's not my question. This has nothing to do with how a light source will be powered, the photocell measures the light output INSIDE and communicates with the timer, so it can compensate with light's output changes. It works and that's why I wish to stay with this timer.

Further, I have the timer, but never moved the enlarger with me, so I'm on to a different setup for sure.
 

ChuckP

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Have you tried contacting Calumet parts department? They may have some around.
 
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Deleted member 88956

Thanks ChuckP, but thus far Calumet is silent and I don't expect anything from that end anymore. Still digging into it. While awaiting some input on here, I will post the answer, if I get one from other sources. All I know at this point is that it needs to be matched as original. Since there are plenty to choose from, guess is not an option.
 

PKM-25

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I had a Metrolux-II with the sensor and now have two RH Designs Stopclock Pro's, one is the compensating type with the sensor. I believe that the two units used basically the same type of sensor, so ordering a sensor from RH Designs through Second Hand Darkroom supplies might get you what you need.

I would also email Richard Ross who is a member here and ask him as he designed all those goodies and might know of the very components you will need or will be able to tell you if you can simply use the RH Designs sensor with a minimum to no adaptation.

Another thing to consider is that although less than ideal in your case, the Zone stuff is no longer made and RH Designs stuff is. I am willing to bet that the Stopclock Vario is every bit as good if not better than the Zone stuff.

It's kind of expensive now but you have to weigh the cost, time, still being made or not benefit factor. I got rid of the Metrolux unit for this reason, opting for current technology that is still being made versus stuff that is getting much harder to find parts for or multiples of for standardization reasons...
 
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OP
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Deleted member 88956

I agree with you, PKM, on the RH performance, although the "old" style controls on the Zone VI work like a charm and are much more intuitive . There is more in my case that meets the eye. Without going into details, I have a sentiment towards Zone VI and parting with it is really not a consideration, especially since the part I'm now missing will cost little compared to another timer. I have contacted SHD, but so far no response on the sensor. It does seem like it should be the same one, as the RH timer came with just a cord to plug it directly in. Thanks for the other suggestions, I'll continue my search and eventually will get the info.
 

Ken Nadvornick

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I believe this may be what you are looking for?

Excelitas Tech VTB8440BH Photodiode, IR-Filtered

From another member's earlier post, I believe this to be the same sensor used by both the Zone VI Compensating Enlarging Timer and the RH Designs Stop Clock Vario. The part number given is: EG+G Vactec VTB8440BH. Detailed specs are included in the link.

I also own and use the Zone VI unit and the catalog image of the sensor in the above link appears to be a very close—if not perfect—visual match, both in form factor and coloring.

And welcome back to APUG (posting, that is)...



Ken
 
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Deleted member 88956

Ken,
The part number you're mentioning (EG+G Vactec VTB8440BH) is it from RH manual or some other good source? Because if that's the case, then it would make sense. I will say though that the early Zone VI heads head a different looking cell.

I do know at this point that what Zone VI used was a Hamamatsu branded photocell, but am still waiting on a reply with actual part number. At the end of the day it is the specs not the brand that count. Will post here when available, but if anyone can pitch in on what Ken has upstairs would be just as good.
 
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Deleted member 88956

Ken,
I have found a thread and saw your reply as above, also saying that this cell looks like Zone VI probes you have, so that is also quite helpful. Looks I'm getting there. Thanks.
 

Ken Nadvornick

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Yes, as mentioned that info comes from another APUG poster. But I do not know his source. Might you be able to PM that poster directly to see if the chain leads back to a hard-copy reference somewhere?

Right before Calumet dropped most Zone VI products I did a "distress" purchase of items I thought might disappear. A replacement light sensor was one of those items. That sensor also matches the appearance of the factory-installed one in my original Zone VI single-tube head, as well as the one pictured in the link.

I have it currently installed in my Aristo VCL4500 dual-tube VC head. That setup is not fully functional in terms of the range of adjustments available at the timer, but it's close enough that I can procedurally work around the constraints.

Ken
 
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OP
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Deleted member 88956

Thanks again, and I'm still waiting for the Hamamatsu reference. They have a number of cells that look the same as this one, but all have different specs and none matches it. So I'll wait and see if the actual original part can be referenced with certainty. Will update it here too.
 
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Deleted member 88956

Ok guys, I have received the specs for the original photocell that Zone VI used. It was a Hamamatsu S1133 photodiode with a blue filter on top (called visual compensation filter). This part appears to have been discontinued according to some on line suppliers, but the photocell linked by Ken above is indeed a very close match. So I am now convinced that it will work as advertised. As you can see the price is next to nothing.

Have just come across the original cell listed on Ebay from Taiwanese supplier HERE Well, just realized this is not exactly the one as it has -14 at the end and differs somewhat.
 
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john_s

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I use an RH Designs StopClock Vario. I had this email exchange with Richard Ross on the subject of the light sensor. I don't know if it's exactly the same as the Zone VI model (models?). There is a post at APUG in which I describe the wiring on my original Zone VI single tube light sensor. I'll find a link to it later.

At 02:19 01/12/2010, you wrote:
>Dear Richard,
>
>I've been using my Stop Clock Vario for several years now and it's a
>delight to use.
>
>Would you be able to tell me the specification/name/model of the
>photodiode that you supply for the Vario? Mine's working perfectly, but
>I'm interested in getting a couple of old enlargers going for use with
>the Vario.
>


Hi John

We sell sensor assemblies for exactly this reason - you can have more than one enlarger. However if you prefer to make your own you'll need a EG+G Vactec VTB8440BH photodiode with IR filtering.

More info at
http://uk.farnell.com/eg-g-vactec/vtb8440bh/photodiode-ir-filtered/dp/1182340?Ntt=118-2340

Wire it so that the pin with the polarity dot goes to the outer pole of the jack plug.

Kind regards
Richard
 
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Deleted member 88956

Thanks john_s, this just confirms what I've received from the man who designed the Zone VI timer. Parts match, and with the Hamamatsu being out, EG+G remains on the table.
 

john_s

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I have found some notes that describe how the sensor is wired for RH Designs units on one hand, and for the Zone VI units as well.

For do it yourself types, the sensor is
EG+G Vactec VTB8440BH photodiode with IR filtering.

More info at
http://uk.farnell.com/eg-g-vactec/vt...0?Ntt=118-2340

Wire it so that the pin with the polarity dot goes to the outer pole of the jack plug (for RH Designs fitting).



The Zone VI cold light head probe was supplied wired to a three-pin DIN socket, as used in old audio equipment. The socket was mounted on the surface of the head. The Zone VI compensating timer and the older stabilizer had captive cable with DIN plugs if I remember correctly. The wiring of the sensor is as follows, using two core (black and red) with shielding:

Photodiode end: black wire to the cathode, which is identified by a small reference hole through the base- see the pdf spec sheet, and
red wire to the other pin. The shield is not connected.

DIN socket end: Black wire to pin 1, red wire to pin 2, shield to pin 3 and linked to the metal case of the socket.
 
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Deleted member 88956

Thanks John, I got the same from PH who's been extremely helpful and responsive to all of my questions.

For anyone who ever thought (or not) of it, I also have a confirmation that sensor can be installed in ANY light source (like a dichro), although (naturally) cold lights have the real output stability issues, but any lamp can fluctuate to some degree.
 

Richard T Ritter

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You may have to take a black marker and cover half the photo cell to get a good range on the timer.
Almost any visible light photo diode will work. The Hamamatsu S1133 photodiode was the one we used in the meters and worked in the cold lights.
 
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Deleted member 88956

Richard, thanks for the input, but could you expand on how photocell interacts with the timer and making it "see" less light expands timer's range?
 

Ken Nadvornick

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I would also be interested to hear any insights, given my issues with the available timing duration range in the VCL4500 head using an original sensor.

Ken
 

john_s

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I have always disliked mounting sensors inside CL heads, and the Aristo VCL4500 is both quite hot and very bright. So I mounted the sensor inside a piece of 0.5inch standard aluminium square tubing in the side of which there is a 0.375inch hole which corresponds to a similar hole in the side of the Aristo unit. The piece of tubing is screwed to the outside of the unit and enough light gets to the sensor. The sensor is held parallel to the mounting surface by a long thin rectangle of glass slipped into the tube. This also acts as a heat protector although it is probably not necessary. I finished the unit in a hurry so that I could use it, and it's not very pretty. I have attached a photo.

The setup is excellent. The VCL4500 unit that I have is the basic one, in which the green tube is on all the time without being able to be varied (except off) and the blue is variable from zero to bright enough to swamp the green almost entirely. The sensor with the Vario unit gives a "first order" adjustment to time if the contrast is altered, so calibration is not as important as I first thought. I am using up lots of random old papers at the moment and when I settle on one or two papers that are readily available here at the end of the Earth I will do a full calibration. At present it's trial and error but not nearly as much error as I expected.

An advantage of having the sensor outside is that it reduces the very powerful light to get values that fit conveniently with the timer (although that is adjustable if necessary)
 

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RH Designs

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This is the part in question, Farnell updated the product code:

http://uk.farnell.com/jsp/search/productdetail.jsp?id=1182340&Ntt=118-2340

As it's a diode the polarity is important; the lead not next to the one marked with a dot goes to the tip on the 3.5mm jack plug we use and the centre pin of the 3-pin DIN plug used on the Zone VI. You can just see the dot at the bottom right of the illustration on the Farnell web page.
 

Richard T Ritter

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The photo cell watches the light and if it changes it tells the timer and the time will lengthen or shorten depending on the out put of the light. this way print number one matches print number 20. I live in an area where the power would change while I'M printing and this causes the out put of the light to change. Once I started testing the timer my prints were consistence. I also did the Fine Prints for Zone VI and would print a hundred prints at a time. The Cold light would change the out put as it heat up and cool down. Before the timer the prints would vary. After the timer the print were all alike.
 
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