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Elroustom
Tinkerer
Username: Elroustom
Post Number: 2
Registered: 12-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, December 23, 2006 - 06:04 pm: | 
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I'm tyring to fix an Oly Trip 35. Got the aperture working, but I don't trust the meter. Any suggestion on testing it, or whether these things die all of a sudden. If it reacts to light does it work, or does how it works vary based on age? |
Brianshaw
Tinkerer
Username: Brianshaw
Post Number: 13
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, December 23, 2006 - 08:18 pm: |
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Check it against the "Sunny 16" rule. Othewise, check it against a known good meter. |
Lucas
Tinkerer
Username: Lucas
Post Number: 5
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, December 24, 2006 - 11:19 am: |
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The meter dies slowly as with all selenium lightmeters as the selenium degenerates.
With the aperture ring set to A, cover the selenium cells around the lense with your hand. Press the shutter, a red panel should become visible in the viewfinder and the shutter release is blocked, you cannot make an exposure. In my experience the ones that do not pass this test have a dead meter.
You can adjust the lightmeter by turning the whole meter but that does not cover low and high light situations. I have four, they go for one- two euro a piece at the thriftshop, and not one of them has the same lightmeter function. I suspect it is the film it self that covers the differences and allows you to make some halfway decent exposures with them. It is a really nice little camera if you want to travel light and do not want to worry about batteries running dry.
I would run a 12 exposures film through it under various lighting conditions and see what happens. |
Arnoldharris
Tinkerer
Username: Arnoldharris
Post Number: 3
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, December 25, 2006 - 03:02 pm: |
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I'm not at all certain anymore about selenium cells dying even slowly. I have 59 Voigtlander Vitessa-T 35mm rangefinder cameras, plus number 60 on the way from eBay. All have selenium cell exposure meters. All are 47-50 years old. Only about three of these meters are dead.
I read notes of more than one repairman who claimed that cleaning the surface of the cells with acetone and/or resoldering connections may revive some of them.
In any case, Magnetronics/UK can make replacements at reasonable expense, complete with potted connecting wires.
Is it possible they lose their power more through moisture than through exposure to light? |
Elroustom
Tinkerer
Username: Elroustom
Post Number: 3
Registered: 12-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, December 25, 2006 - 06:28 pm: |
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I'm not at all sure I have what I can call an answer here - since I've gotten a yes, a no, and a maybe. But I thank you all for your contributions. I will work on this camera further and report my findings. |
Proofblue
Tinkerer
Username: Proofblue
Post Number: 14
Registered: 01-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, February 26, 2007 - 07:40 pm: |
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My trip 35 is fine - selenium meters only degrade on contact with a moist atmosphere for a while. Arnold Harris is right - any stuff you might have heard about sunlight degrading them is tosh. If it passes the test mentioned above it should be fine - I took my whole lens assembly to bits and rejigged it, which involved taking the cell out, and it now takes better pictures than it did before! A camera I like very much...Good luck with it! |
Jimmomary
Tinkerer
Username: Jimmomary
Post Number: 1
Registered: 08-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, August 02, 2008 - 04:24 pm: |
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I just found this post, obviously later in time. I've worked for 28 years at a selenium copier drum factory where we vacuum deposit selenium onto cylinders. Selenium in the ultrapure state (five nines), acts as a photo conductor/photo receptor. I.e., insulator in the dark and progressively more conductive with light. Hence, its applicability to measure light. As selenium sits and is exposed to UV, heat, chemical vapors and just oxidation, the surface begins to crystallize, ruining the photoconductive properties. Deposited selenium is always amorphous (like glass), and as it 'dies' it changes to a crystalline solid, which is conductive all the time. Various dopants are added to selenium to prevent, or delay crystallization. The main dopant is arsenic, in very, very low percentage. Don't worry, we're not talking rat poison here, just physical chemistry. Imagine a drum in a xerox type machine, all that scrubbing of paper and toner and wiper blades. That application demands high resistance to crystallization. A light meter needs less, and I think not everyone knows how to grow a stable selenium film and make it last for decades. It's a black art, with the techniques held close to the chest, as it were. Selenium was used in early diodes and transistors too. Today silicon has replaced selenium universally. It's more sensitive, better in color response and seldom crystallizes. It can't be used one for one for selenium, the circuits need different parameters and biases. Remember the Nikon F2AS ? The 'S' was for silicon, the first use by Nikon in its cameras. The common phrase always kicked around anymore is 'silicon photo-diode', that should be vaguely familiar.There's your Selenium 101 class, students. Quiz next week. Yell if more is needed. Jim M. |
Nickon51
Tinkerer
Username: Nickon51
Post Number: 13
Registered: 05-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, August 02, 2008 - 09:29 pm: |
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Hi Jim,
Thanks for the 101 on selenium. I used to work on photocopiers when most of the drums were selenium coated.
There was a widespread practice in the industry of polishing the surface of the drums with "Brasso". I wasn't keen on doing this, but I used to wear gloves and a mask. It did bring up a "flat" drum to good performance again.
Is there a way to do this on meter cells? ie if the cell is not dead, would it be worth trying?
Cheers
Greg |
Mndean
Tinkerer
Username: Mndean
Post Number: 60
Registered: 08-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, August 02, 2008 - 10:03 pm: |
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Hm, I'd heard different in regards to color response, that selenium was closer in color response to the eye than CdS cells (I'd forgotten which way the bias was in CdS, toward UV or IR), which were the replacement for many years until silicon cells became common. I may be misremembering things, though, it could've been CdS vs. silicon. It was many years ago that I'd read on this. |
Charlie
Tinkerer
Username: Charlie
Post Number: 169
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, August 03, 2008 - 06:09 am: |
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I think selenium does not vary resistance according to how much light it sees but generates electricity according to how much light it sees. That's why it does not need a battery. And I hav read that selenium is closer to the human eye in color reaponse than CdS. |
Arnoldharris
Tinkerer
Username: Arnoldharris
Post Number: 37
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, August 10, 2008 - 06:21 pm: |
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I as much about chemistry as I do about astrophysics. In other words, what I pick up from reading daily newspapers.
But I have a big collection of Voigtlander Vitessa-T 35mm rangefinders, all built in 1956-1958 and all with neat little selenium cell exposure meters up on the top right front. That was 50-52 years ago.
All but a few of them snap to attention in the presence of light.
Now, based on what you all tell me, how is that possible?
I'm not saying how accurate they are any more. But why are they moving at all, instead of just lying there as dead as rusty nails?
Arnold Harris
Mount Horeb WI |
Mndean
Tinkerer
Username: Mndean
Post Number: 65
Registered: 08-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, August 10, 2008 - 07:49 pm: |
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Well, I didn't say anything in regards to selenium cell life - I couldn't do it since I have a number of selenium meters over forty years old which still work. Not all are accurate, but they work. Of all the cameras I've gotten with selenium meters, only one was DOA. |
Thuggins
Tinkerer
Username: Thuggins
Post Number: 34
Registered: 12-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, September 04, 2008 - 04:03 pm: |
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Complete instructions for troubleshooting and repairing the Trip 35 are here:
http://www.thermojetstove.com/Trip35/
And it is "tosh" that "The meter dies slowly as with all selenium lightmeters as the selenium degenerates." I have found ones where the cell has degraded and the output is reduced to a greater or lesser extent. But generally in my experience they are very reliable, much more so than CdS meters. |
William_a
Tinkerer
Username: William_a
Post Number: 2
Registered: 09-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, September 09, 2008 - 01:41 am: |
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When you put the selenium ring back on the camera, there is a little U-shaped metal piece that needs to go onto a round metal post on the inside of the ring that you turn to set the ASA. As you turn the ASA ring, this will cover or uncover a certain percentage of the selenium cell to adjust for the ASA. I almost missed this because it was not mentioned on the thermojetstove Trip 35 site mentioned above. However otherwise that site was very helpful. Unfortunately my rear lens assembly is no good because it was somehow discolored, possibly by grease that got on it when I opened or perhaps before I opened it. There was lots of grease between all the rings in the lens assembly. I started another string on this yesterday here in case anyone has a suggestion. (buy more Trips for parts?) |
