Built in selenium light meters

Quality Light Metrics at 7060 Hollywood Boulevard Suite 415 Hollywood CA 90028 Ph # 323-467-2265. They can repair these !

www.antiquecameras.net

It is not easy or cheap to repair a 'dead' selenium light meter. In some cases just the soldered or welded wires are corroded, in most cases the selenium cells are exhausted. Also, those selenium meters usually give more or less correct readings in daylight only in most cases - most of them are not sufficiently accurate or sensitive for indoor or low light shots. Any cheap CdS meter will give better results. The bottom line is that I think in most cases it is not worth the efforts to get them repaired, if it is possible at all.

I don't know if this will help, I got it from the subclub's web site. A company in the U.K. called Megatron manufactures selenium meter replacement parts.

http://www.megatron.co.uk/page.html

Apparently a custom cell with leads costs about $30.00 U.S. (maybe a bit more now with the declining greenback?). If you have any luck with them please let us know, I would be very intersted!

By the way, there is a fellow named Henry Scherer who has a site all about Contax cameras. In that site, he has a page about the selenium cells in Contax IIIA cameras. On that page he discusses some of the reasons for selenium meter failure. The failure reasons are probably generalizable to all selenium meters. Usually, it is not the contact wires corroding, but as Winfried pointed out, cell exhaustion. Scherer explains what "cell exhasution" actually entails. I found it very interesting (the whole site is actually chock full of info, especially if you like Contax cameras.) http://www.zeisscamera.com/#IIImeterrproblem

Most cells I have worked on had corroded backs; and worked again when cleaned with an eraser. A few with moisture problems were dead; due to the bond shorted. Cells exposed to light degrade with time; ones left in sunny used camera stores are often of low output. I have a Russian Lennigrad selenium meter from 1959 that reads within 1/2 stop of my Luna Pro; I'm not sure if cells kep in cases actually ever degrade at all. My dads GE Selenium meter from the mid 1940's still works OK; but is off about a stop low.

With a Retin IIIc; most all repair guys told us the cell was dead; this urban legend is common. An old repair guy in Jupiter Florida tackled the repair about 10 years ago; and did the "clean" the corrosion off the cell gambit. The meter today still works well; and has little error.

Many of these meter circuits work in short cicuit current mode; the cell area and light determine the current.

If the meter died during a shock; suspect the movement being un-pivoted. If the meter died while being stored; suspect corrosion on the cell contacts. If the meter reads low; suspect corrosion; and or cell degradation due to radiation/light. The National Camera repair course of the 1970's gave me the above three pointers; which have worked well for me.

Frank Marshman got the meter on my Vitessa-L working by replacing the coil, but then it died again a month later. A selenium meter isn't particularly more accurate than the one between my ears or the exposure guide on the film box, so I don't see much reason to repair them.

Further to Kelly's post... The following is from the Contax web site above (thanks for the great link BTW!). Like everything to do with fixing old cameras a little thought and caution may make the difference between success and disaster. The message here seems to be that gold plated electrical contacts don't corrode.

<<<<<<<"There is a story going around through various web sites that there is a simple fix for a IIIa light meter that doesn't work. According to these experts the problem is oxidation of the electrical contacts to the photocell and that all one needs to do is to remove the cell, take a blade and scrape the contacts. This is supposed to restore the meter to normal operation.

The fact is that about one of every five IIIa camera I receive for servicing has damage to the cell contacts caused by scraping. This damage adds a fair amount of work to the camera servicing because it is necessary to repair this damage by polishing out the scratches and replacing the gold plating that was removed by the surface being scraped. Zeiss understood corrosion, and in most of their light meters the cell contacts were gold plated to eliminate the possibility of corrosion and to ensure long term good electrical contact.">>>>>>>>

Just thought this passage interesting and worth noting (of course maybe it's just me, because I have an old Contax III that needs serious professional attention).

Cheers!

I have a couple of contax IIIa camera's with working light meters...although this helps their resale value they aren't much more useful than a good understanding of the sunny 16 rule. They are easily fooled by backlighting and need a good understanding of light to be used correctly anyway! More than a meter repair by anyone but yourself (if you are so inclined) I would recomend reading:

www.fredparker.com/ultexp1.htm

My thanks to Kelly for the tip about cleaning the corrosion from the selenium cell component with an eraser. I had previously opened one of my junkstore Westons and gained a small improvement by scraping the copper strap. However, this recent exchange inspired me to dig deeper and to apply the cleaning effort to the metalic disk, the copper ring underneath, and the star-shaped spring which overlays the assembly. The result is that one of the old Weston II meters is now working perfectly, and I'm probably going to try again on the other.
    About the only tricky thing in the disassembly is getting off the back cover which is held in place by two slotless screws. My solution was to file down the soft metal barrel of a ballpoint pen and slightly deform it with pliars for a tight fit. You also need to be careful to note the positions of pieces at disassembly, and to not lose the small pieces including the the little spring that tensions the button at the bottom front of the meter and the brass stud that fits loosely in a hole at the meter's top under the back cover.