I have used a silver oxide battery since the 80s, with no modification to the camera
A couple of Spoties I have gotten from ebay have worked as well with the solver and the weill cell (yes I was stupid enough to try one)
and I could not see a difference.
Maybe I have just been lucky
Originally posted by wombat2go Looks like the Spotmatic could be OK with the silver oxide. Do you know if it was ever recaibrated after the change to silver oxide? -there is a trim resistor on top of the cds ldrs.
Years ago in the spotmatic discussion group a seires of tests were carried out, let me see if I can dig those files....
Originally posted by wombat2go Titrisol, That is very good.
About the use of silver oxide batteries, they have a plateau of 1.55V compared to the 1.32 V of the original mercury cells.
Ref 5 is not citing silver oxide as a replacement as far I I read, and the diagram P23 shows it is not a balanced bridge, so will be affected by battery variation.
Perhaps the use could be qualified with a comment that accuracy might be affected especially at low apertures/low light.
I have seen some reference to a shottkey diode being put in a container with a AgO cell but I don't know if that will fit in a Spotmatic.
That would be a more accurate option if it is possible.
By the way I don't have direct experience with the Spotmatic because don't have one here. Perhaps I need one now!
However I restored a 1960's HoneyWell Pentax Exposure Meter by re-designing its electronics to slightly more modern tech - I put article on Apug DIY about that.
Unencumbered by an aperture, it works from EV18 to EV3; I just took a EV4 reading in the office, it said , at iso 400, f/8 and 1 second, and the exposure was very good on the K-01 at that setting