Mamiya 7 65mm Lens: Replacing a Broken Flex Cable
Originally posted on Instagram. Notes from the repair bench, kept here as a searchable archive. View the original on Instagram
This Mamiya 7 65mm lens came into the shop with a very common issue: broken flex cable. This cable connects the shutter to the camera connection pins on the rear of the lens and transmits aperture and shutter speed information. The symptom of a broken flex cable is that the meter in the camera does not work as the aperture information is not being transmitted from the lens to the body.
The video shows how I can quickly check the lens by putting it on a fixture with an ohmmeter reading the relevant pins. In this case, the lens was set on f/22 so there should have been a steady reading of around 2.3K ohms. When the focus ring is moved, you can see that the reading on the meter jumps to zero at some point because of the damaged flex cable making poor contact. Solution requires a disassembly of the lens and removing the shutter to take off the old flex and install the new one. Since the rangefinder unit is removed for access to the cable, it gets re-calibrated.
Photo four shows the shutter ready for some de-soldering and attaching of the new flex cable assembly. The new cables are show to the right of the shutter on the bench.
Photo five shows a close up photo of the broken flex: the trace of the first connection to the left has a tear that is visible.
