Yashica MF meter readings

[farlymac]

I was in Radio Shack today, and they had some 675 batteries on clearance(Mercury no less), so I decided to get some and fire up my Yashica MF so I could run a test roll through it.

After cleaning the crap out of the flash battery bay I put in two AA's. Then I checked the meter battery hole, and it was clean. I still took a pencil eraser to it to make sure of good contact, and after waiting the prescribed time post removing the blue pasty from the battery, I installed it and took a peek in the viewfinder. Not what I expected to see. The needle was at the f16 mark, and I was indoors with the ASA set to 100. I turned around to face away from the window, and it dropped down to just above f8. So I figure it is working, put the cap on the lens, looked again, and it was right at f8. That was strange, I figured it would be all the way down around the bottom of the scale at f2.8.

The battery has been in for about three hours, and the needle, with the cap on, is now at f5.6. When pointing the camera at the computer screen, the needle rises to f8 when I take the cap off. Could this just be the metering circuit not having been used for so long, or should I assume that RS's listing of the 675 at 1.4VDC is correct (not just someone rounding off the figures), and the circuit is being overdriven? BTW, the flash circuit is working.

PF

 

[Leigh Youdale]

My understanding is that mercury batteries ceased production in 2000 - so what you've got is probably at least ten years old. What that means as far as retention of original charge is anybody's guess.
Second, static DC voltage tests don't provide the true picture. They need to be tested on a multimeter and under load i.e. with the connected circuit switched on. (Not easy to do when installed in a camera).
I recently had to check a partly used 9v (nominal) battery that showed 7.45v static but dropped to 3.4v under load. Needless to say it wouldn't run the device it was supposed to!

 

[farlymac]

I checked the meter again this morning, and it is now down to just above f4. The static reading went from 1.38vdc last night to 1.37vdc this morning. You're right Leigh, it is hard to read the battery in camera, but I might give it a try if I can find some really fine wire to make a test lead from the bottom of the battery well.

I now suspect there may be a malfunction in the meter system causing a drain on the battery when the cap is on, or making the meter active when it shouldn't be. Could be a breakdown of some component that regulates the sensitivity of the circuit. Most things I can think of though would kill the circuit if they go bad, so I'm looking for someone with experience on this camera to see if they have had this problem, or something simular. Or maybe it's just the way it works, but I don't want to waste a roll of film in it if I'm not confident in the readings I'm seeing.

Also, the batteries are dated to be good until April 2014, so they are new stock. My understanding is they are Silver-Oxide, but still have some Mercury in them, thus the disposal message on the back of the packaging. They are just not a true 'Mercury Cell'. And not quite a Wein Cell either, though you do have to wait after you remove the seal all the same.

PF

 

[farlymac]

The meter tonight is reading f4 with the cap on, so that is down from the f8 it was at originally two days ago. Any ideas? Does the meter need adjusting, or a part replaced?

PF