Mamiya Super 23, adjustment.

[Daire Quinlan]

Hi All, I have a Mamiya Super 23 with RF problems.

I have adjusted the rangefinder as recommended in countless discussions using the two screws straight/angled for infinity/close focus respectively. Still has a problem. Namely, that I've nailed the closest focus distance, that's super sharp, but then it starts to drift quite dramatically from there. At about 10 feet it's about an inch, 30 feet it looks like a couple of feet. The Infinity focus screw is just a stop , it's the close focus screw that actually 'adjusts' the RF so to speak. I've seen mention in a couple of discussions of adjustments deeper in the rangefinder for adjusting the tracking, so it looks as though I need to tweak them.

Anyone ever done this ? Or have a repair manual or something ? Others have had the same problem but have settled for just adjusting for maximum sharpness at (say) 10 feet or so, whatever distance they'd most likely use the camera at.

I only have the 100mm f/3.5 so It's not the lens, I have the ground glass, at its infinity stop the ground glass registers the lens as being on infinity.

 

[Daire Quinlan]

Hmm actually, thinking about this on my walk into work this morning, I've come to the conclusion that most of those discussions on the internet about adjusting the Super 23 (and by extension the universal) rangefinder are actually wrong. What's commonly referred to as the 'infinity adjustment screw' doesn't actually result in any adjustment at all, it's just an infinity stop. The only adjustment screw is the angled one, and that only enables you to correct linearly for distance.

Short of getting into the innards of the rangefinder, if there are some more tracking adjustments in there, it strikes me that the only way I can correct this is to use the angled screw to ensure the rangefinder is accurate at infinity, and then adjust the brass ring on the back of the lens at the close focus distance, by selectively shimming only that side of it that makes contact with the RF pin at close focus distance. This brass ring is held on with 3 equidistant screws, suggesting that it's probably intended to be shimmed if necessary.

D.

 

[chrisaisenbrey]

You can easily find/google the service manual for the polaroid 600SE . The rangefinder should bet the same:

Chris

 

[Daire Quinlan]

Good call, I was looking for the Universal all right, never occurred to me to look for the 600SE as well. It's here for anyone interested.

 

[Daire Quinlan]

Soo ... I ended up messing around with this on saturday night to try and dial in the focus at both close distance and infinity. I didn't really succeed, partly because I don't understand the function of the eccentric screw that's mentioned in the repair manual. The 600se is almost exactly the same as the Super 23 incidentally, at least from the POV of the RF mechanics.

So basically the repair manual says to use the RF adjustment screw (the one that's at 45', commonly referred to as the 'close focus adjustment' on most discussions that talk about this) to adjust for infinity, and then if the close focus / RF distance is outside of stated allowances (basically about 1mm on the focus ring) to use the 'eccentric screw' to compensate for this. It doesn't go into details :-D

The eccentric screw can be turned, and you can adjust for close focus distance all right, but then infinity is out of whack again, so I'd use the other adjustment screw to re-adjust for infinity, which would throw close focus out of whack again, necessitating another fractional turn of the eccentric screw, which meant the infinity needed adjustment etc etc etc

I went through a couple of iterations of this, and couldn't get both lined up perfectly, so I settled on making sure about 6 feet was dialled in properly and put the top back on again.

Anyone else any experience with this ?