Mamiya 7: No Power from Crusted Battery Contact
Originally posted on Instagram. Notes from the repair bench, kept here as a searchable archive. View the original on Instagram
This Mamiya 7 arrived here with the complaint of no shutter release and no display. Basically no power.
When put on the test equipment and the shutter button is pressed, photo two shows the results: zero current. This issue could be caused by a bad battery, battery cover issue or corrosion on the body battery contact. But even if one of these was the issue, generally you would see some sort of current flow even if it was not enough to energize the circuit. In this case, batery power is not going anywhere.
First thing I would do after a visual check is clean the battery contact inside the camera using a fiberglass bristle brush pen (seen in the background in photo four). The contact looked very clean, but still no go. So, maybe a connection failure. Not common but possible.
Photo three shows the battery box and the contact after some disassembly of the camera. In photo four, I show the contact removed from the battery box. Still looks very clean, no corrosion visible and after brushing it with the cleaning pen, it still would not work. Looking at the contact with eight power magnification, I could see a thin crust on the surface of the contact. This would not clean off with my more gentle cleaning methods so I ended up using a needle file to abrade the surface of the contact.
After reinstalling the contact in the battery case, the camera powered up and all was well again. Photo five shows the camera on the test equipment with the shutter button pressed and the 8.5 mA flowing through the camera.
I still don’t know what would have caused such a hard deposit on the battery contact. It was not battery corrosion. Environment?
