Mamiya 645 Pro: Battery Drain Caused by a Loose Spring
Originally posted on Instagram. Notes from the repair bench, kept here as a searchable archive. View the original on Instagram
This has been a week of Mamiya 645 Super/Pro repairs. I have serviced a lot of these cameras and this is the first time seeing this issue: camera (645 Pro) came in with battery drain complaint. Checking current draw showed 2 mA at all times, even when the main switch was in the locked position. This would drain the PX28 battery rather quickly as these batteries have a capacity of around 155 mAh so that would mean in theory, the battery would last only 77 hours but in practice, I would doubt that it would be able to power the camera for any more than half that time. Upon disassembly, I found a small spring (shown in the center of the photo) wedged in the main switch which was grounding the switch to the body and keeping current flowing at all times.
While checking out the operation of the camera, it was now working properly, no battery drain. But after about a half dozen shutter cycles, the camera locked up. So I had to do a much more deeper disassembly to find the problem and re-attach the loose spring.
The second photo shows the 2 mA current when the main switch is first depressed. The third photo shows the near zero (1 micro amp) current when the camera is at rest in locked position. One micro amp is within specs for the 645 Pro. The 645 Super, which was not as refined, allowed up to 10 micro amps at rest.
