I have a Hasselblad C12 back that has a gear synchronisation issue with the body. It has been tested on two working bodies, one of which has been serviced very recently, so the issue lies definitely in the back.

I performed a CLA with this video as my basis. I turned the indicated spring loaded gear 1.5 turns after initial tension was felt, and placed the gear with the dog leg so that the notch on the bottom of the gear was on the right of the white plastic lever, as per the video instructions.

However, this did not fix the gear sync issue. I expect the indicated gear to be the culprit. Do I need to turn this gear more than 1.5 turns? Could it be that the spring inside this gear is worn out?

This photo was taken before (rather, during) the CLA. This also explains the missing pin.

enter image description here

  • \$\begingroup\$ Given the complexity of the the mechanism and the degree of age and wear in your particular example, I would not be surprised if the issue is elsewhere. I mean the fix old cameras guy mentions a “sweet spot” at one point and that is something only identified by touch and experience...and all the videos mention this as an element in success. Was the back working recently? What are the exact issues now? How many times have you retried the reassembly? Have you adjusted the wind counter? Is the picture from before cleaning? Is the nylon plate ok? \$\endgroup\$ Commented May 21, 2021 at 11:41
  • \$\begingroup\$ I bought the back in this condition (pic is also before the CLA). Wind counter is left unadjusted as it appears to be working fine. Nylon plate appears in good condition. The issue now hasn't changed, in that the gears when winding to the next frame will desync and fight each other, causing the back to get pushed off the body \$\endgroup\$
    – timvrhn
    Commented May 21, 2021 at 13:06
  • \$\begingroup\$ Back pushing off the body sounds like more than the video addresses...it seems to be about misaligned frames. Misalignment of gears seems like more than a spring. Your photo doesn’t show the pin. Is it missing? Also the video suggests that seating the pin is a bit involved. My intuition is that more spring tension is not the prime suspect to misaligned gears. Maybe something is upside down. Maybe there is a mechanical failure that explains the barn find appearance. Were it me, I would set it aside and let my understanding develop. \$\endgroup\$ Commented May 21, 2021 at 13:52
  • \$\begingroup\$ @BobMacaroniMcStevens good catch, I had taken out the pin before taking this picture. The video is not about my issue specifically, but it does address the indicated gear which does appear to influence the turning rate of the gear with dog leg, which also happens to be the gear connect to the body's \$\endgroup\$
    – timvrhn
    Commented May 21, 2021 at 14:03
  • \$\begingroup\$ If the dogleg is not working, why? Or that is the direction I would start looking at causality. Take the gear that drives the dogleg out and see if the dogleg engages correctly. Then that gear back and the next one out...and so on. The spring is furthest away in the causal chain. \$\endgroup\$ Commented May 21, 2021 at 17:36


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