Mamiya Sekor 55mm F/4.5 TLR Lens fast shutter at 1/8th

Hello

I recently bought a nice Mamiya Sekor 55mm F/4.5 TLR Lens. When it arrived, the shutter was gummed up, with the main shutter spring stuck. I've taken apart a couple of these shutters, so I roughly know my way around it and what areas need a clean and lubrication. After freeing the main spring, cleaning the slow shutter assembly with isopropyl alcohol, and re-lubricating the lens, the lens sprung to life, and when comparing speeds to my other lens, it sounded about right.

Strangely, though, 1/8th of a second fires at 1/500th and is the only slow shutter setting that acts like that. 1/15th is fine, and 1/4th is fine. Has anyone encountered this before? I've had it apart twice now, and I can't spot anything.

Cheers

Check the M-X flash synch switching mechanism.

On the speed-setting cam, is there a swage mark under the flat for the 1/8 setting? If so maybe it was overdone and the stud sits too high...

Hi, thanks both for your help. I've managed to fix the problem; I cleaned and relubricated the flash sync mechanism. After taking it out for a test run, the lens works great.

Thanks for your help.

Glad we could help.
Based on experience, I can confidently recommend that anyone using any of the Mamiya TLR lenses should make a habit of regularly checking the position of the M-X switch. There is a reason that many of the used lenses out there have the switch glued in the "X" position!