Mamiya 7II: No Flash Sync from Broken Shoe Safety Switch Pin
Originally posted on Instagram. Notes from the repair bench, kept here as a searchable archive. View the original on Instagram
This Mamiya 7II arrived with a complaint of no flash sync. Looking under the flash shoe after removing the flash shoe spring, I could see that the safety switch pin was damaged and not fully depressing to actuate the flash shoe safety switch (photo two). The switch disconnects the flash shoe from the flash circuit unless a flash is installed. This prevents the flash high voltage from appearing on the contacts if you happen to be using the flash plugged into the pc socket with no flash installed on the shoe.
Photo three illustrates the difference between the damaged pin on the left and the new pin on the right. The next photo shows the new pin being installed after removing the switch assembly. Photo five shows the safety switch when no flash is installed and the next photo shows the switch with a flash installed in the shoe and the switch depressed.
The first photo shows the camera during final testing and all looks good. The bottom meter on the Kyoritsu tester shows infinite resistance which is good since this tests the insulation of the flash circuit. The top meter indicates flash efficientcy and this camera tests at 85% which is good and in spec.
Most cameras with flash shoes have this type of safety switch to prevent someone from getting shocked if no flash is installed. But, if the small plastic pin breaks, the shoe will no longer be active so this is the first thing to check when a camera has an inoperative flash shoe.
