Not sure how many of you have a Nikon F with the FTN finder like mine, but I made a discovery this week that I wanted to share.
I've read that many of the FTN finders are dead, as the resistor ring can have issues and none of the repair shops I've talked to have parts for these anymore. I've also read that many FTN finders had issues with the contacts in the battery chamber making good contact with the two batteries. Mine worked great for the first three weeks I had it, with two old PX625 mercury batteries I had around since the late 1980's.
But then it developed an issue where it would just stop working. I would take off the battery cover, try to pry the top contact out from the wall of the battery chamber to make better contact with the batteries, then drive myself nuts with my big gorilla fingers trying to get the battery door back on. With the door off and me holding the batteries perfectly in the middle of the battery chamber, the meter worked fine. Then I'd struggle to get the door back on and by the time it was finally in place, the meter no longer worked.
I was ready to give up on it, when I saw this auction on the evil eBay:
http://www.ebay.com/itm/NIKON-F-PHOTOMIC-FTN-TN-METER-PRISM-BATTERY-ADAPTER-/151718676694
I have no affiliation with this seller aside from buying one of his adapters. He recommends using a 1/3 N battery with the adapter. I put in a 1/3 N and naturally the meter, which is calibrated for 2.7 volts, was inaccurate with the 3.0 volts of the 1/3 N. Although there was no more problem with the meter not getting juice from the batteries.
Then I discovered the 675 size hearing aid batteries at the local Walgreens (at 75¢ each), which are 1.4 volts, and two of them fit perfectly into the above adapter, giving you 2.8 volts. I found that with my FTN, it is now as accurate as it was when I first got it and it was working with the old mercury batteries.
So I wanted to pass this along to others who might be having similar trouble with their FTN finders. The thing I like most about this solution is that the 675 size hearing aid batteries are plentiful and inexpensive. So hopefully I'll be able to use them for a long time.
Best,
-Tim