Meter cell as in the power source.
I got a very nice Nikkormat FT last year from a seller here. The meter needle was jumpy, but it cost a pittance and was fine & clean otherwise.
A few weeks ago, I decided to clean the resistor and wound up with a nicely operating camera, no more jumpy needle and the meter was accurate. I picked it up the other day, and the meter was inactive. I had left my last active mercury cell in it, the thing was 17 years old! It had exuded wetness into the battery compartemt, so I cleaned it and stuck a fresh 675 in. Meter was way off. Took the 675 out and it's voltage was about 1 but climbing. Strange.
I put the ohmmeter on the battery contacts with the meter turned off - should be infinity, right? Right. Nope, it was about 140 ohms!! The exudate from the mercury cell had gotten into the porous (phenolic?) insulator for the contact finger at the bottom of the compartment and rendered it conductive. The resistance varied according to the polarity of the ohmmeter. I removed the contacts from the body, cleaned it, and got the resistance up to about 6k ohms. Boiling it in distilled water got the resistance up to about 250k. At the moment it's sitting in a little jar full of active silicagel, to get as much moisture as possible out of the insulator - but I have a feeling I'll be drilling out the rivet and making a Delrin insulator.
Just a heads -up in case anyone is having an obscure battery drain problem.
I got a very nice Nikkormat FT last year from a seller here. The meter needle was jumpy, but it cost a pittance and was fine & clean otherwise.
A few weeks ago, I decided to clean the resistor and wound up with a nicely operating camera, no more jumpy needle and the meter was accurate. I picked it up the other day, and the meter was inactive. I had left my last active mercury cell in it, the thing was 17 years old! It had exuded wetness into the battery compartemt, so I cleaned it and stuck a fresh 675 in. Meter was way off. Took the 675 out and it's voltage was about 1 but climbing. Strange.
I put the ohmmeter on the battery contacts with the meter turned off - should be infinity, right? Right. Nope, it was about 140 ohms!! The exudate from the mercury cell had gotten into the porous (phenolic?) insulator for the contact finger at the bottom of the compartment and rendered it conductive. The resistance varied according to the polarity of the ohmmeter. I removed the contacts from the body, cleaned it, and got the resistance up to about 6k ohms. Boiling it in distilled water got the resistance up to about 250k. At the moment it's sitting in a little jar full of active silicagel, to get as much moisture as possible out of the insulator - but I have a feeling I'll be drilling out the rivet and making a Delrin insulator.
Just a heads -up in case anyone is having an obscure battery drain problem.
