RB67 6x7 120/220 Power Driver

wjlapier

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So, I'm cobbling together another RB67 and purchased a Pro S back that said 220 ( orange ) and 120 on top. Didn't think anything of this thinking It was a back that could use both 120 and 220 film, but after reading some I realized the back was at one time a power driver. Was it common to remove the power driver and put a bottom that would be from a manual crank back? The seller didn't reveal the info at first but was pretty cool with explaining a few things about the back. I do realize the back has interchangeable 120/220 pressure plates, and the back is setup for 220 ( can I use 120--I think I can ).

Any info on this back and the conversion from power driver to non would be great.
 

Marco Gilardetti

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I don't get your question. If you want a manual crank back, just buy one and resell the motorised back without tampering it.
 

mshchem

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I'm not an expert, I know Mamiya made a 6x8 power back. Flipping the pressure plate over should allow 120 film. I believe these units had their own batteries. If you Google RB67 POWER BACK you will find examples . Really pretty cool.
 
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wjlapier

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There is the 6x8 power back, but before that one there was a 6x7 power back. The one I have doesn't have the motor on the bottom, so I'm wondering how it was removed and if this was common back in the day. The back looks like just about any other 6x7 Pro S back except the 220/120 label on top with the 220 in orange color. The pressure plate easily comes off and it appears there is a 120 plate you could exchange out, but I don't have that plate.



 

WilmarcoImaging

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Can you please post more photos showing the bottom of the back assembly? Is an electrical connection present? If yes it is a first generation 120/220 6x7 power drive back. Can you please post several photos showing the innards of the insert?

The drive mechanism is part of the insert, as is the 120/220 identifying tag. It seems unlikely, but not impossible, that a normal 6x7 non-power back was converted to 120/220.

Have a look at the Butkus site for the manuals.
 

Marco Gilardetti

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This back variant is very unusual, and this was actually the first time that I've seen it. Usually motorised backs have a completely different layout and shape. However, there are pictures on the internet showing something that was possibly it, complete of other parts:

 

mshchem

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Looks like you're missing the battery pack. Later versions put the batteries in the back itself. The pressure plate is usually able to flip over to accommodate 120 film.
 

MattKing

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I have the power supply part of that back, but no back to go with it. I got it in one of those "buy everything all together" purchases.
 
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wjlapier

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The bottom doesn't have a way to plug in the battery pack.
 

WilmarcoImaging

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It can't be a power drive back if there is neither electrical connection, nor battery compartment.

A non-motorized 6x7 120/220 back seems unknown. I just checked the Pro-S system chart, and the Pro-S manual and didn't see this type of back listed.

How likely do you think the back was cobbled together from parts of several film magazines? Where did it come from prior to your ownership?
 
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MattKing

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I believe the OP is saying that his back shows signs of having been modified.
 
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wjlapier

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I purchased the back on Ebay recently. I figured it must have been modified at one time. That's why I asked if it was common at one time to remove the motor part of the back.
 

Marco Gilardetti

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wjlapier said:
That's why I asked if it was common at one time to remove the motor part of the back.
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I'd say no by any means: this is the first time that I see it. And I also wonder about the purpose: buying a motorised back and then a standard back to scrap parts from is more costy than buying two separate 120 and 220 standard RB backs (plus, you'd have two perfectly working interchangeable backs).
 

Mamiya_Repair

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My first post - this back did indeed start out life as a 120/220 Roll Film Power Drive. At some point, the power drive parts were removed and a standard bottom installed. You need to change out the bottom cover and also the bottom mechanism plate as the power drive has a bottom swing out supply spool holder since there was no room for a spring loaded one in the motor compartment. Also, the take up spool driver is quite different than the normal 120 back. Although some of the top cover parts are different, you can still use the back manually. I did have a customer request that I convert his power drive 120 film holder to manual to save weight and it was not a problem since I had a large stack of broken 120 film holders in the shop.

This setup with the separate power supply was discontinued when the new style 6x7 and 6x8 power drive film holders were introduced.

I have been servicing Mamiya products for 40 years and I will say that the 120/220 power drive backs are not that common

Bill
 

ic-racer

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Does it work? That is, does it count correctly based on where the pressure plate is positioned? For example on the Yashica 124g, a little pin senses the status of the pressure plate to stop winding at the correct frame (12 or 24).
 

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It is clearly a modified original 6x7 power drive back that needed a bottom mounted driver to function as one. However here the bottom part was replaced with standard back part. I'd be surprised if counter did not work correctly in 120/220 mode as that is at top plate and not modified. Interesting iteration.

SD 6x7 power back was basically same as 6x8 and an all in one design, so as easy as any standard back to swap.
 
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