Contessa selenium meter repair

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Cascadilla

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I recently acquired a Zeiss Contessa (folding from 1953-55) which works well except for a dead selenium meter. Is it possible to repair this or replace the selenium cell?
 
Contact George Milton of...

Quality Light Metric Co.
7095 Hollywood Blvd. #550
Hollywood, CA 90028
323-467-2265

He's fixed four of my meters so far...call and ask if he has the parts needed to fix yours...
 
Henry Scherer has replacement selenium cells from the last European manufacturer to make them, before shutting down in about 2010. He can overhaul your camera too. However, you need to realize that he has a huge waiting list to get service done.
 
Robert Lai said:
Henry Scherer has replacement selenium cells from the last European manufacturer to make them, before shutting down in about 2010. He can overhaul your camera too. However, you need to realize that he has a huge waiting list to get service done.
Click to expand...

And an even bigger ego...........
 
Cascadilla said:
I recently acquired a Zeiss Contessa (folding from 1953-55) which works well except for a dead selenium meter. Is it possible to repair this or replace the selenium cell?
Click to expand...
I've been pondering this issue the last few days myself. Hard information on how the cells were made and what they were coated with is not so easy to find online. I'm not sure some of the information that is out there and often regurgitated is necessarily right anyway, Eg. exposure to light killing the cells. I don't think it's that simple. I've found a reference suggesting a combination of exposure to light and humidity encourages them to oxidise internally, leading to a reduction in cell output, so personally I'm not persuaded that exposure to light alone is the problem. Humidity and deterioration of the coating used to seal the cells is likely to be more of a factor than the net amount of light exposure a cell has accrued, I think. And in order for humidity to be a factor in the first place, one might argue that the integrity of the cell coating would have to be suspect for it to affect the cell?

In some cases at least, camera manufacturers knew how to rejuvenate a poorly perfoming cell to make it good again. How did they do this? Zeiss Ikon had a testing case for meters, (the VE33) with instructions on how to regenerate the cell. Noone I know of has ever seen this case, or can elaborate on exactly what this regeneration process was. It was the topic of a discussion here at RFF a few years ago. I have the same manual referred to in that thread. No other details about the regeneration process are offered in it. I would be very interested to hear from anyone who can fill in the gaps. We have some German members; surely somebody's father, uncle, grandparents, must have had a connection to one of the firms involved in making the cells, or the cameras that used them? Anybody know a person connected to Gossen back in the 1950s or 60s, for example? The case in question must have been available to some dealers and service agents, so I find it frustrating that more knowledge existed sixty years ago about solving what can be one of the more troublesome problems involved in repairing certain cameras, than seems to be available from anyone today.

More generally, the tips Mike mentions on his site are worth trying. If the cell itself is capable of producing the electrical output needed the issue is probably getting the current through the circuit to the galvanometer and back to earth. The cell itself is quite likely to be the point at which the circuit continuity is poorest, so improving this is always worth a shot assuming one has the skills to access the cell. I've bought some conductive glue for my next adventure in selenium meter repair to see if I can improve my strike rate with this type of meter failure, but, I would love to be able to do something about the actual cells themselves when they go brown bread.
Cheers,
Brett
 
Although I'm a chemist, inorganics isn't my strong point. However, reading the ever-reliable Wikiwikiwawapedia:
http://en.wikipedia.org/wiki/Selenium#Physical_properties
it is the grey form that is used for the photocells, and seems to be the most stable form, as gentle heating (to about 180C or 400F) converts the other allotropes to grey. So, I can see how a bit of heat treatment could effect this, though ideally you would want to exclude air, which is possible in the middle of a flame where much of it has been used up.

So, if the selenium itself has gone west by some sort of disruption due to loss of its pure grey allotropic form, maybe there is a way back. However, it has electrical junctions with both the front and back surfaces, which are necessarily across the entire area, and if these were unserviceable, I don't know how they could be repaired. Maybe heat treatment could permit enough softening to restore contact. I don't exactly have these things lying around to try it on though!

No idea if this helps.

PS I have recently bought two Zeiss 1960s RFs with working selenium meters, so maybe this is another option, to transplant one?
 
johnnyrod said:
Although I'm a chemist, inorganics isn't my strong point. However, reading the ever-reliable Wikiwikiwawapedia:
http://en.wikipedia.org/wiki/Selenium#Physical_properties
it is the grey form that is used for the photocells, and seems to be the most stable form, as gentle heating (to about 180C or 400F) converts the other allotropes to grey. So, I can see how a bit of heat treatment could effect this, though ideally you would want to exclude air, which is possible in the middle of a flame where much of it has been used up.

So, if the selenium itself has gone west by some sort of disruption due to loss of its pure grey allotropic form, maybe there is a way back. However, it has electrical junctions with both the front and back surfaces, which are necessarily across the entire area, and if these were unserviceable, I don't know how they could be repaired. Maybe heat treatment could permit enough softening to restore contact. I don't exactly have these things lying around to try it on though!

No idea if this helps.

PS I have recently bought two Zeiss 1960s RFs with working selenium meters, so maybe this is another option, to transplant one?
Click to expand...
It is helpful, because it adds a bit of information I wasn't aware of regarding which form of selenium is actually used in the cells. I was up until well into the small hours the other night reading about selenium (including the Wikipedia article) but most likely too tired to make a lot of sense of it by then, so thank you.

Searching for information about photovoltaic cells almost invariably produces hits for modern solar cells, Eg. silicon cells, but almost nothing about selenium cells in terms of how they were made. If selenium photovoltaic cells come up in a discussion about photovoltaics, it appears, from my looking, to nearly always be in the context of relative efficiency (around 1% apparently, very poor compared to modern solar panels), or historical context or development of more modern materials and designs. Because technology has moved past them now, and they are no longer much used for photovoltaic applications except perhaps in photocopying I've yet to find any hard data on the actual manufacturing process.

Cheers
Brett
 
I don't think it's a process you can really do at home. I've forgotten the details but the top conductive layer is very thin, maybe by a vapour deposition process. The back plate can be substantial as it isn't necessary to be transparent. I would think the PV selenium cell is basically the same thing.

To elaborate on the Wiki article, allotropes are different forms of the same elemental material. That is, it's a pure element but adpots different structures which gives it different properties. Graphite, Buckyballs, graphene and diamond are all allotropes of carbon - they are pure carbon in different atomic lattices.
 
Thanks for the replies so far--I may be brave and they the Mike Elek procedure since it doesn't look totally intimidating...
 
Tried the Mike Elek procedure, but no luck. Oh well, the shutter, f/stops, rangefinder and film advance work well, so it is still a pleasure to use. Thanks again for the information.
 
I think at this stage, in the absence of any data about Zeiss Ikon's mysterious, (or should that be, mythical?) VE33 kit, I want to progress this problem, so I am going to keep an eye out for an old toaster oven of the type used for toasting sandwiches or small pizzas at my local markets or garage sales. I will try heating some stuffed cells up at various temperatures and then recoating them, and see what transpires. Given the unhealthy implications of ingesting or absorbing the wrong forms of selenium, in the wrong dosages, having an inexpensive device dedicated to camera repairing tasks seems the smarter option, than using the household oven. It won't, obviously, heat the cells in an oxygen-free environment, but that can be plan B, as it would involve a suitable flame and a respirator, and closer personal proximity to the cell during the process. These things may well come to nought, but, until tried I won't know.
Cheers
Brett
 
The easiest way to get an oxygen-free atmosphere is to seal a vessel ike a jar, with something burning in it. It'll burn out when the oxy is gone, leaving nitrogen, CO2 and the trace air gases, including moisture. Not sure how big a deal the moisture will be (you could add a desiccant I guess) but at around 200 C/400 F the CO2 isn't going to do much oxidising. The selenium isn't going to go anywhere, I'd happily do this in a domestic oven. Not entirely thoguht through how you could seal something like a jar or tin, then get away with heating up and cooling back down without it bursting/collapsing. Ideally you'd have a vessel with a gas inlet and vent, and have steady flow of nitrogen through it the whole time, and it would take care of the expansion/contraction itself. Something like a Quickfit lab glass flask. Not easy to get nitrogen at home though! If you are a welder then argon is easy to come by though, or you could try with CO2 from a home brewing kit.
 
Try my super easy procedure before Mike Elek's

Try my super easy procedure before Mike Elek's

mconnealy said:
I got mine working following Mike Elek's instructions. It was a pretty simple fix.
http://elekm.net/zeiss-ikon/repair/meter-repair/
Click to expand...

The Contessa meter is definitely a head scratcher. More often than not, I have had success reviving the meters, at least temporarily, with a procedure that is much easier than the one on Mike Elek's site. To see my procedure, with pictures, go to my free eBay guide. Temporarily Revive the Light Meter On Zeiss Contessa 35 Others

In one of my other free eBay guides, I discuss how to test fire the Contessa shutter. Test Fire the Shutter On Zeiss Contessa 35mm Ikonta
 
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It's been some time since I posted regarding reviving dead cells so you might be forgiven for thinking I'd given up or lost interest in this topic. Actually, I've spent a lot of time poring over whatever old documents I could find about selenium cells. Old patent documents. Online libraries. And more.

Modern literature is of little assistance. Selenium cells are often mentioned, but usually as little more than background history to modern cells with references to their inefficiency leading to modern alternatives. And much of the relevant documentation is pre computer, let alone pre internet. But I've found a few references that do, at least, suggest an initial direction investigations of cell renewal ought to take. No, it doesn't involve directly heating the cells, either, or the consequent risks involved in fumes from such processes. All for the better, of course.

A few observations.
  1. The ability of cells to vary their electrical resistance when exposed to light seems to have been generally of more interest to earlier researchers. Of course this property was exploited in earlier burglar alarm systems, Eg. triggering alarm systems in response to flashlight beams and so on. The ability of some cells to actually produce electrical output was of interest but not always the primary interest.
  2. Cells could possess their own individual characteristics, earlier versions, anyway. Some would demonstrate increasing resistance when exposed to light. Others, less. Some cells demonstrated a tendancy to polarise their response to current. Others, not.
  3. Cells with an ability to generate electical current flow used to be referred to as "generators". The best generator cells were usually polarised.
  4. Cells could be "matured" by the application of small amounts of electrical current. To keep a selenium cell matured it was recommended to ensure they were stored in conditions of low humidity, not to overheat them, and to expose them to light every few days (avoiding excessive periods of exposure to light).
There's more to it than the above and, frankly, I'm still working my way through what little I've been able to unearth and getting my head around it. But at this stage, I believe the way forward will involve investing in a variable power supply to enable me to make some preliminary tests on deteriorated cells. I've no way of being certain, unless someone actually manages to unearth a surviving VE33 kit.
Cheers
Brett
 
Dear Brett,
I managed to talk to a semi retired technician who did work for the Spanish importer of Zeiss Products back in the day. The Spanish importer was Rodolfo Biber, who worked at Zeiss in Stuttgart but was taken to Madrid to take over the Zeiss Product distribution and servie after the former one (who was operating since the 1910's retired). The name Rudolf Bieber evolved into Rodolfo Biber which gave name to the business (an inc.). He retired and passed away in 1994 and it's her daughters who run the company.
Anyway, to make a long story short. That technician worked in Barcelona and was the authorised repair facility for Zeiss Products. And told me he never, ever saw or heard anything about the VE33 kit. Maybe it was something they had in th Stuttgart factory.
But he told me how they regulated selenium meters back in the day.
They unsoldered the resistence and soldered a variable potentiometer instead
Then they compared readings with a perfectly calibrated hand held meter and tweaked the potentiometer until readings both in n high and low light were ok.
Then unsoldered wires and measured the potentiometer's values and soldered a resistance of the required value.
My contina-matic IIa has some black patches glued crudely over the cell,Maybe mine was too sensitive, deliverng too much current, and that patch was fitted in the factory, as it had never been opened.
Best regards
Robert
 
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