Mamiya RB67 Sekor C MX SYNC switch

Hi,
I have just bought a used Sekor C 180 mm and found that the MX switch is on the M position. I can't slide it on the X position. I thought that it might be broken, but on looking at my 50mm Sekor C where the switch is in the X position, I find I cant move it to the M. This camera is so full of interlocks to prevent accidents, maybe there is a special proceedured to do the switchover. I think it is unlikely that they are both broken. Or is that a weak point in an otherwise bulletproof system.
Unfortunately I do not have a manual for the Sekor C's . Can anyone help?
thx;

It's possible that a previous owner has glued the switch on the 50mm to the X position to prevent it accidently moving.

Whilst it is possible that the switch has also been fixed in the M position for the 180mm lens, this seems unlikely.

I have both of these lenses and I'm not aware of any interlocks.



Steve.

i think you have to depress the switch in to slide it to the other position on these lenses, cheers, john.

Thanks John... What a dummy! Pressing the switch then sliding it works great.

Thanks John, I will remember, getting my first RB in a couple of weeks !

Peter