F-1n and Ftb battery check w/ 675 batts.

[ronwhit]

I have both a Canon F-1n and an Ftbn in which I use a # 675 hearing aid battery with an "O" ring to power the meter. The battery check function does not work in either camera using this battery, although the meters themselves seem to give a correct exposure reading as compared with three other cameras, and "sunny 16" guidelines. Is there something inherent in the 675 batteries that make would cause this to happen? For example, although they are rated at 1.4 volts, do they have a different current output compared to the old mercury 1.35 volt batteries?

Also, if I use a 1.5v alkaline battery in either camera, the check function works, and I get a pretty consistent 1 stop under exposure meter reading. Is this common? If so, it seems easy to compensate for this by halving the ISO/ASA setting.

 

[MattKing]

The battery check function might depend on the side of the battery making contact with the battery chamber. That would be defeated by the "O" ring.

EDIT: Jon Goodman (here on APUG and elsewhere) sells a simple, inexpensive, no circuitry "625 shaped" adapter that solves this problem - you insert 675 batteries into it.

 

[E. von Hoegh]

I have both a Canon F-1n and an Ftbn in which I use a # 675 hearing aid battery with an "O" ring to power the meter. The battery check function does not work in either camera using this battery, although the meters themselves seem to give a correct exposure reading as compared with three other cameras, and "sunny 16" guidelines. Is there something inherent in the 675 batteries that make would cause this to happen? For example, although they are rated at 1.4 volts, do they have a different current output compared to the old mercury 1.35 volt batteries?

Also, if I use a 1.5v alkaline battery in either camera, the check function works, and I get a pretty consistent 1 stop under exposure meter reading. Is this common? If so, it seems easy to compensate for this by halving the ISO/ASA setting.

It's possible that the zinc/air 675s won't deliver enough crrent to check OK on your cameras. I use 675s in a LunaPro, a couple Nikkormats, and a Nikon Ftn - the battery check function on the Ftn and LunaPro functions normally.
Alkaline batteries are useless for your purposes; the voltage starts out at about 1.6 per cell and falls throughout the life of the cell - meter accuracy is dependant upon the cell/battery giving constant voltage.

 

[flavio81]

You have pretty good taste in cameras!

I think the 'current' explanation is probably the best.

 

[Jeff Kubach]

The batteries last a good while, have 2 spares just in case.

Jeff

 

[mklw1954]

I use this inexpensive adapter with 675 batteries in several cameras, no problems:
http://www.paulbg.com/Nikon_F_meter_batteries.htm

 

[ronwhit]

thsnks and an update

Matt - thanks for your suggestion regarding the adaptor made by Jon Goodman. I've placed an order with him. A great guy to deal with.

flavio81 - thanks for your comment on my "good taste" in cameras. I started with an Ftb over 41 years ago, and I still use it on occasion.

I measured the height of the one mercury battery I have left, and it is about .026 thicker than a # 675. That alone could contribute to some problems, and so Jon Goodman's adaptor seem to be a better solution than adding an "o" ring to a # 675, at it appears to also make up the thickness difference. Stay tuned....

 

[ronwhit]

update....

After trying Jon Goodman's adaptor in the F-1n, the Ftb, and a Canonet GIII 17, I can definitely recommend it. It worked fine in all three - much better than a # 675 with an "o" ring or with the metal ring from a dead Wein cell. Full disclosure - I have no relationship with Jon other than being a happy customer. I believe a key thing that Jon's adaptor does is make up the difference in height I noted in an earlier post. Also, it provides the same configuration as the old mercury cells.