Correct Procedure for Winding Mamiya Pro-SD Back?

[kram]

<p>I recently got an RB Pro-S and a Pro SD 220 back. I am having problems with it.</p>

<p>It seems to work fine early in a roll.<br>

Here's what I do:<br>

1. Shoot a frame.<br>

2. Cock the shutter.<br>

3. Either wind the film with a stroke of the back's winding arm -or- I move the "release thingy" [see my picture.] then I wind the arm. Both methods work- <em>sometimes!</em><br>

The problem I'm having is that the backs wind arm will freeze in the out position [see pic] or the back will just keep winding and never get to stop point.<br>

Any advice would be welcome.<br>

<img src="http://markcolman.com/blog/rbback.jpg" alt="" width="576" height="1297" /></p>

[andre_noble5]

<p>The release thingy is not normally used. It is used to wind through an unfinished roll to the end without the normal need to expose each frame before winding.<br>

<br /> This doesn't answer your full question but is a start</p>

[kram]

<p>Andre, thanks. I read the manual and it appears that my back is somehow defective as the wind arm will lock in the open position and won't release unless I take the back off and use the release thingy™.</p>

[andre_noble5]

<p>Major,</p>

<p>When your tax refund comes in, just go on KEH and get a motorized 6x7 back in EX+ condition for $133.<br>

This back allows both 120 and 220 film use with a simple rotating of pressure plate.</p>

[kamal_passi]

<p>thanks for sharing</p>