Is it possible to replace the selenium in selenium light meter?

Discussion in 'Classic Manual Cameras' started by kevin h. y. lui., Aug 17, 2007.

  1. I know inaccuracy of selenium light meter is a very common problem in classic cameras. Most of them response to light but it is over/reduced some stops. I have read some books about repair cameras and the writer says we can add/remove/disconnect resistor(s) so as to make it accurate again. I, then want to know, is it possible to replace the selenium directly?
     
  2. I think Radio Shack has some in their catalog. If not you can probably Google up other sources.
     
  3. Megatron are a source of replacement selenium cells in the UK, but whether a cell of the same size would have the same output as one in an old camera, and how you could calibrate the meter across the light range is probably more of a problem than just fitting a new cell. http://www.megatron.co.uk/ Often another issue is the variable resistors used - these go bad in many meters (eg Kiev, Nikon Photomic)and may not be replaceable.
     
  4. Look, when a meter goes bad it needs to be serviced, and that includes recalibration. One can't simply replace a part that's suspected to be bad and get accuracy at any light level or linearity. If you want to have your camera's selenium cell meter made right, perhaps Quality Light Metric (google for them) can do it. Odds are that you can't do a good job yourself.
     
  5. I cleaned time ago a selenium cell of a Russian meter with acetone and it worked. Also, I have to say the meter wasn`t totally dead. Nevertheless intelligent people prefer to send it to repair. One of the best places is: Quality Light Metric Co, 6922 Hollywood Blvd, Los Angeles CA 90028-6117 USA Tel: 213-467-2265 Interesting: http://www.xs4all.nl/~tomtiger/zenrep/meter.html
     
  6. Kevin, you seem to be aquiring a large number of Classic Cameras recently... if you intend on using them, a solid hand-held light meter is probably a very good investment. Selenium cells have a varied life and Ive read that in some cases they died shortly after leaving the factory... others have held on for over 40 years still producing perfect exposures. There is wide speculation as to why and how these cells die, as well as a multitude of recommendations on fixing them. A trained professional with an understanding of electronics and access to devices for calibrating light-meters is probably really the only reasonable answer. In some cases, purchasing a second example of the camera with a working meter may be cheaper than a meter repair. In my limited experience; even when working properly, most Selenium meters have a very limited range and can be inaccurate in low-light conditions. Ironically, the situations that these meters are the least accurate are also the ones where you typically NEED a working meter! Ive found that many times these meters are unresponsive indoors and during low light like near sunset, despite there being plenty of light to take a photograph! There are also many lighting situations where it is sometimes difficult or straining to view the meter needle in the viewfinder of many old cameras.... this includes low light as well as situations which cause glare and flare, or if the subject is predominantly dark on one side. In these situations a hand-held meter is simply easier to read and less of a headache! A hand-held meter will give you the ability to work in lower light, to expand the kinds of metering you can do, and allow you to use high-speed films which the older meters cannot calculate for. It will also allow you to use cameras without their own light meters in tricky lighting situations. Another advantage is that having one meter which you use for all cameras means you get to know the quirks of that meter and can learn to read it very quickly. This is opposed to having, as an example: 10 different cameras with 10 different meters all responding to light slightly differently. Also you might be able to find a reliable light-meter for the cost of repairing the meter in ONE of these 10 cameras. The exception would be if this is your MAIN camera, in which case a repair as well as having a second body on-hand might be warranted. There are also many cameras which have automatic shutters that are completely dependant on the meter circuit, and due to this limitation repairs are really your only option to continue using them! Also due to those limitations, these cameras are often not very expensive, (unless the specific model is rare or collectible) so purchasing a second body may be much cheaper than repair. Theres a ton of options out there, and its really a different topic all together!
     
  7. Oh, also be aware that many old hand-held meters are also Selenium powered... and these are just as likely to fail, and sometimes very limited in low light as well. I personally don't like LCD screens and prefer the dial kind of light meter... during the 1960s and 1970s many meters were made which have a dial and are battery-operated CdS cells. I believe the later Weston Masters took batteries as well as the Gossen Luna-Pro. Today Sekonic makes several light meters with a dial-type display for those of us old-fashioned types who prefer seeing all the options at once instead of one at a time... those include professional models as well as simple budget models. Even the budget versions have a greater sensitivity range than even professional Selenium meters, and ANY meter found on a classic camera.
     
  8. Patrick is right, as usual, but if possible, avoid meters that need old mercury batteries
     
  9. Thank you very much. It seems that fixing a selenium meter is quite a difficult job. I want to fix my Retina IIIc 's selenium light meter. When I take it out, I found the light meter response to light but not accurately. It is sad , I think , to see the meter lost its function and become a decoration of the whole camera. I have Gossen Luna-Pro. I brought it few months ago and it comes with spot attachment and enlargement attachment. It comes from a film-retired photographer. It react to light accurately, more than the previous one I have. I put 2 LR44 batteries in it rather then finding the wein cell or zinc-air battery. The needle falls into correct place when I press the test button. I dislike LCD meter. It is because the screen usually become haze when the surrounding is too bright or dim. I can not take the reading. I borrowed a pro Sekonic meter before, It is too sensitive that it jumps when a car pass by or a man walk pass. I prefer the needle display one because the adjustment can be make easier.
     
  10. Yeah, unfortunately its just one of those quirks when dealing with Classics... Ive got a Minolta SR-3 with the removable coupled meter... the meter doesnt work, but at least its removable so it doesnt take up space on that beautiful camera!
     
  11. Most all the "bad/poor" selenium metered cameras and meters I have worked on just ha bad contacts; and decenct cells. The peanut gallery always wants to "push" that the meter is bad; and avoid getting a good contact with the cells contacts. The meter circuit works in short circuit mode; the cell is a current source with currerent proportional to the light. ANY poor connection makes the meter read low. The dogma of replacing the meter cell could be done on your car too. Next time there a cable problem; just pay to have the starter and battery replaced; and never think a poor cable to battery could be a problem. :) All it takes to "fix" an typical meter is a dumb eraser; and a smart person whe is not brainwashed that meter cells need replacing. A decent source of another cell is just another meter or camera; often buy into the dead cell dogma; and are afraid to try an eraser. With a meter cell that has a fracture that is growing thru its core; the active cross sectional area drops; the meter reads low. "repairing" meters was covered in the 1960's national camera books; and the 1950's Pop photo how to articles. With a 53 year old Kodak IIIc about every one that had a punk meter just required an eraser. Then as a repair person you just let the dumb customer believe their dogma of the dead cell; its sounds meter to show an invoice with parts; then all labor :)
     
  12. Typically a selenium meter circuit produces current proportioanl to the light intensity; the meter coil has a low resistance; thus its in a short circuit mode. The DC meter coil swings an arc angle proportional to the current. With a slight typical sock drawer storage of a seleenium meter/camera; the contacts on the cell grow more resistive. This added resistance adds to the meter's super low resistance of its coil; the meter swings less angle; it reads low. Think of a car with a poor corroded battery contact/clamp. Only a total dufus would replace a starter or battery; without checking for a loose or poor battery connection. In cameras; its the norm to preach "replace the cell". With no electrical load on the cell; the cells voltage is shunted/capped by the internal diode action of the cells junction; typically less than a volt. When its used as a lightmeter; the cell is working close to short circuit mode; the internal diode action of the cells junction is not shunting the cell at this time. The meter cell must have decent non corroded contacts for it to work as designed. An old meter or camera very often just requires an eraser to fix it. IF the camera/meter was bumped; the meter movement might be off; the jewel broken. IF the cell has had water or mechanical shock; its active surface are can be less; it will read lower. If the camera was left in a stores sunny window; the cell can be abit burnes; ie read low due to long exposure to light.
     
  13. "the meter coil has a low resistance; thus its in a short circuit mode. The DC meter coil swings an arc angle proportional to the current. With a slight typical sock drawer storage of a seleenium meter/camera; the contacts on the cell grow more resistive. This added resistance adds to the meter's super low resistance of its coil; the meter swings less angle; it reads low." Not quite true. With a "super low resistance" the meter would need quite a bit of current to get moved... typically the meter coils have resistance values in the range of hundreds of ohms. A slight increase of contact resistance will not matter too much, but a totally corroded contact will.
     
  14. All very interesting, but it doesn't explain what I see with my old Weston Master II selenium meter... It responds well to light - TOO WELL in fact. When "sunny 16" would say use f/16, it says use f/22, and generally says that exposure should be about a stop less than seems right. This is the opposite of what you'd expect with dirty contacts, somewhat burned out cells, etc. Fortunately, since it's consistent, one can just compensate. Partly, this may have to do old ideas about what the film speed scale should be, but I thought that was only about 1/3 of a stop different (ie, film that would be ISO 100 now was rated in Weston's eyes as 80). So I'm puzzled...
     
  15. Kevin, This morning I when for shooting with one of the rangefinders and as I was to do it with a 135 mm, I used the Luna Pro with its spot attachment. I have not the Adapter Pot so I was forced to use zinc-air batteries. Blow me! I hadn`n any. So I fitted two silver 1.5 v. Testing it vs. the Digisix the lecture was quite similar. So I decided to leave the silver 1.5 v. for ever. (Till they exhausted)
     
  16. Radford, Due to my poor sight I was forced to let my Weston V in the desk. It worked for lots of years but now is going a little lazy. If I want accurately reading It should be set to 650 ASA if I`m using 100 ASA film. Maybe is as tired as me
     
  17. "I believe the later Weston Masters took batteries" Which Weston Masters were these? I've never seen a battery in a Weston Master or Euromaster but am always willing to be enlightened.
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  18. Kevin, if you are not willing to spend the money to have a professional job done on a very old and outmoded technology,then use a handheld light meter. If the camera is worth using (think "lens"), then it is worth taking the time to meter the shot with a reliable meter.
     
  19. Sorry H.P., my bad... good thing I added "I believe"... you really would be stunned at some of the things I believe. :)
     
  20. Luis, my Luna-pro don't need to have a adapter when using the LR44. It is true. When I use Zinc-air batteries, the needle falls out from red zone. Only LR44 can falls in and stopped in the meddle. When I am need to use zinc-air battery, I would add 1/4 or 1/2 stop to correct the metering error. (This is the problem on my luna-pro only) I must agree that the needle is rather, too thin that you won't be able to see it in some conditions. Also, this is the thickest meter that I have. Jeff, It is sad to see the meter on the camera is not working and the repairing cost is high. :(
     
  21. http://elekm.net/zeiss-ikon/repair/meter-repair/
     
  22. Don... thats awesome. Maybe I should try taking apart that old Minolta SR Meter!
     
  23. I should also try it on my Retina IIIc too. Thanks!
     
  24. Winfried; the meter coils are NOT hundreds of ohms; but usually an order of magitude less or more. The added resistance of a faultly connection DOES add to the meters internal resistance and the typical old sock drawer camera/meter reads low just due to bad contacts. The meter swings an arc due to the DC current thru it. It has less current thru it when there is corrosion. Its the MOST COMMON FAILURE MODE in the hundreds of self powered meters I have worked on. In many cases one would get a meter/camera declared dead by a user; who even had another repair chap declare it dead. In once bought a pile of old selenium meters off of ebay for next to nothing; all with the repair tags from a repair outfit. The resale ONE meter paid for the entire lots cost; the next was gravy. Having "contact issues" with low impedance ciruits is nothing new to electrical equipment.

    In many places in the USA there is a heck of alot of humidity. Decades old cameras and meters are often stored in dresser drawers. The TYPICAL amateur unearths them during an estate sale, the meter is declared dead; the repair chap then fixes it with an eraser. This type of "repair knowledge" was common in the USA when folks used self powered meters more; in the 6 volt car days. The "repair" is documented in the 1950's Pop Photo magazine Feiningrs workshop column; and in the National Camera Repair courses in the 1960's.. Its old hat common knowledge for a repair chap to check battery terminals on cars that wont crank; and meters that are dead in cameras; for over 7 decades.

    The statement of "With a "super low resistance" the meter would need quite a bit of current to get moved.." is bogus and flawed; techically totally Palookaville stuff. The meter movement is spring loaded with a torsion spring. The meter swings due to the torque which is directly proportional to the DC current. Thus is called the motor constant; ie Newton meters of torque versus amps; ie current. The meter movement can in fact have ZERO resistance and still work; the meter runs on DC current. One can replace the meter coil with another coil of different resistance; the meter/rotary motor still will have the same motor constant in torque versus current.

    What makes the meter movement swing is DC current; a few milliamps.

    In checking meters on tests the swing of the meter versus DC current in milliamps or microamps to see it it meets the specs. Then the meters short circuit current is measured versus several light levels. Many times all is good and the the darn thing works CORRECT just because one took the meter cell brackets off; and re installing the cell dislodged the crud/corrosion.

    With some meters there is no adjustments; except the meters zero torque/bias of the torsion spring can be bulled around which does a global offset; usually done for decent tracking with full sunlight.
     
  25. As someone else mentioned often the problem isn't the cell but connections that need to be cleaned or resoldered.
     
  26. Kevin, I fitted the Luna Pro with 2 SR44 (the ones I use with the Nikon F2) plus two rings to make contact. The silver batteries where completely new. After some shoots the meter didn`t arrived to the red zone. I went back home and with a battery tester I checked them: one was ok but the other was only 0.01 v. Yesterday I tried changing the bad one with a fresh one. At the bigining averything was right but after an hour hapend the same and the meter failure and didn`t arrived to the red zone. Went back home and the meter was ok again. Do you think could be because with the movement the rings don`t make good contact. But what happened first time when one of the batteries went dead? Thanks for your help
     
  27. Luis, Sorry for my ate response because I am too busy that I nearly forgot this post. I am using LR44 (alkaline battery) and does not have any problem with me. I have never tried to use it with SR44. In the first case, it is unusual but I know it does occur in some cases, like you put 2 new fresh batteries in to the radio but soon one of them is ran out of power. (And then the radio can work) I also want to know the reason too. I think, would it due to the 2 rings caused internal short circuit inside the battery house?
     
  28. Kevin, Thank you. You are always kind. I`ll buy a couple of LR44. Meanwhile, maybe I have to do as Rick Olesson suggests using insulated wired around the batteries. http://rick_oleson.tripod.com/index-111.html
     
  29. Luis, I am waiting for your good news. (But mine has a problem w/ the Retina IIIc again) :O(. And it is very kind for Rick to share his experiences too.
     
  30. Kevin, I deplore to hear that. Maybe Chris Sherlock can help you. http://homepages.ihug.co.nz/~Srawhiti/KodakRetinaRepair.html http://homepages.ihug.co.nz/~Srawhiti/KodakRetinaRepair.html I got 2 X LR44. By the moment the Sr44 are working perfect. Hope good news from you abaut very soon.
     
  31. Luis, Thank you very much for your kindness. I have visited Chris page and bookmarked it. However, I have a feeling that the problem that I am facing (you may refer to http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=00MMqy ) is not easy to solve. I also have a sense that it might owing to last time when I sent it for Cleaning and lubricant the shutter, the repairman has loosen something inside the shutter or the focusing mechanism. That is good to hear you luna pro is working well with SR44. If you said the needle will fall on the red zone when using sr44, then using LR44 might not the same result. There is 0.2V differences between 2 X SR44 and 2 X LR44.
     

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