Mamiya 645AFD not autofocusing

Discussions regarding Phase One 645 AF and Mamiya 645AFDIII Camera

Mamiya 645AFD not autofocusing

Postby NNN637326840358185914 » Mon Aug 10, 2020 6:24 pm

I have a Mamiya 645AFD that hadn’t been used in a couple of years. I decided to put it to work again. Fresh batteries, etc. However, I immediately encountered a problem. The camera is stuck in manual focus even when the focus mode selector is set to S or C. At first I thought it might be the mounted lens so I switched lenses. Same thing. Next, I checked the focus on a couple of lenses by using a small screwdriver to operate the focus receiver on the lenses. They all turn smoothly and move the focus ring. Then I examined the focus driver on the camera. It pops in and out just fine when the focus selector is moved from S or C to M. Next I determined that the driver and receiver are engaging correctly by turning the focus ring on a lens mounted on the camera moving the focus selector from S to M. In M the focus ring turns freely, in S or C there is drag. That proves engagement. When depressing the shutter release I can hear what I assume is the focus motor operate for a second or so but the lens does no focus.

I have experience working on delicate electro mechanical devices so I decided to partly disassemble to see if I could determine more about where the failure happens. The focus selector on the front of the camera body seems to have both a mechanical and an electrical function. When M focus is selected it withdraws the focus driver device that engages the focus receiver on the lens. That part is happening. There is a set of gears indicated by the red arrows in the attached photo that appear to have a function in auto focusing. One is attached directly to the focus driver. If that gear is turned manually the focus driver and the other gears also turn. However, although I can hear the focus motor run when the camera fires, the gears indicated by the red arrows don't turn.

The focus motor is below a flat connector strip which has several branches. Exposing the motor further would involve disassembling several additional components and at this point I’ve gone about as far as I intend to go without further information. Although I hear a noise that I’m assuming is associated with focusing I can detect no motion from the focusing motor itself, including by feeling for tiny vibrations.

Questions:

1. Is this a known problem with the Mamiya 645 AFD?
2. If yes, what is the solution?
3. If that involves replacing parts, are the parts still available?
4. If it’s a possible repair, what’s the approximate cost?
5. If the autofocus is not repairable would the camera still work in manual focus with a digital back, or a film back, or both?
NNN637326840358185914
 
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