Mamiya 7II: No Power Caused by Energizer A544 Battery
Originally posted on Instagram. Notes from the repair bench, kept here as a searchable archive. View the original on Instagram
This post is for users of Mamiya 7II cameras.
The Mamiya 7II that was on my bench today had an issue that had me a bit perplexed. Complaint was that there was no shutter release or meter visible. Sure enough, no lights in the viewfinder. First thing that I do is, of course, check the battery. Battery voltage is fine. Contacts are clean. This is a bit odd. I put my test battery in the camera and it works fine. Hook up the camera to the test equipment power supply and all looks fine, no battery drain and pulling a little less than 8mA with the meter on which is correct.
Now my attention goes to the battery (Energizer A544). I notice that it has a very small protrusion on the positive terminal (photo two). I discovered that this tiny raised bump was contacting the insulated center of the battery cap and causing no power to the camera. Now this would only be a problem with the Mamiya 7II as the cap for the Mamiya 7 (shown on the left in photo three) does not have this plastic insulation and has a fully metal surface.
The video shows my test of the cap and battery: a tiny bit of movement puts the positive terminal out of contact with the battery cap and then no power to the camera.
So, if you have a Mamiya 7II look carefully at your new battery as if it is an Energizer A544 you may have an issue. I don’t know if this is a defect on just this batch of batteries or if they are all like this. Actually I don’t recommend the Alkaline battery for the Mamiya 7/7II and think you will do better with the silver oxide batteries.
