Minolta Autocord shutter and Fresnel

OAPOli · Jul 5, 2023

Recently got an Autocord and tuned it up. I have a couple questions.

1. When cleaning the screen my memory lapsed. How is the fresnel oriented? Grooves on the gound glass? I tried both ways and it doesn't seem to matter.

2. After cleaning the shutter (Seikosha MX: cleaned and lubed the escapement, cleaned and lubed cocking ring and cam) the speeds are approximately 1 stop off. No big deal of course but wondering if I could do better. I tried pivoting the escapement outwards but after a certain point the shutter doesn't cycle properly.

OAPOli · Jul 5, 2023

To clarify: I'm used to the 1/500 and 1/250 being off. But generally the remainder can set to at least 0.5EV tolerance.

ic-racer · Jul 5, 2023

Too slow?
Oil on the escapement?

OAPOli · Jul 5, 2023

Yes, all too slow. Escapement is pretty clean, I just oiled the axle on the gears/wheels.

Dan Daniel · Jul 5, 2023

Usually the fresnel grooves face the ground glass, so the fresnel grooves and ground glass are sandwiched in the middle. But as you found, it doesn't make a big difference. The advantage lies in being able to focus on both the ground glass and the groove lines at the same time (yes, I know, not much difference).

The right side screw on the escapement also has movement. Loosen both screws and then tighten. Do what you can to adjust the left side, then move the right side, then move the left. I bet there is a simple pattern to this but I don't know it. In general, though, the right side seems away from center?

Also those Seikoshas are often pretty greasy on the blades and such and can benefit from a thorough cleaning. Not going to get close with dirty blades.

OAPOli · Jul 5, 2023

Thanks! I wasn't able to tune it further. I guess a teardown would be required. It's strange because 1/25 and 1s are pretty close but the rest are about 1 stop over.

ic-racer · Jul 5, 2023

OAPOli said:
Thanks! I wasn't able to tune it further. I guess a teardown would be required. It's strange because 1/25 and 1s are pretty close but the rest are about 1 stop over.

The fast speeds are too slow, in that case how are you measuring? They may be OK, depending on how you measured.

250swb · Jul 5, 2023

The Fresnel side (the matt side) faces down towards the mirror. As for lubing anything without knowing that simple fact and I wonder what damage you may have done. It's very easy for oil to migrate from the shutter mechanism to the shutter blades and then you get a sticky shutter. Fingers crossed you didn't apply too much lube.

dxqcanada · Jul 5, 2023

You have to take it all apart and clean everything ... especially each blade and the plates the blades are sandwiched between ... then loosen the speed escapement up again.
Move the upper pallet end closer to the centre ... if the shutter gets stuck then move it away from centre.
Check the slow speeds first.
If the slower speeds (~1/25s) are slow then move the upper pallet end closer to center.
Then check the higher speeds ... if they are slow, then move the lower retard end away from centre.

I have had to do this routine with a shutter about 4 times before I got all within 1/3stop.

Suggest taking the LCR course on the secret website.

Dan Daniel · Jul 5, 2023

OAPOli said:
Thanks! I wasn't able to tune it further. I guess a teardown would be required. It's strange because 1/25 and 1s are pretty close but the rest are about 1 stop over.

Oh, ok, then the speed pin can be bent. When you cock the shutter, a small arm swings out (or in?? sorry, bad memory- the speed cam is stepped on either the inner edge or outer edge, the arm with the small pin swings to rest against the speed cam). The pin is a medium gray metal. Take a pair of needle nose pliers and bend it towards the speed cam steps. It will be hard to grab hold of, and bending is a gentle slow operation, meaning give a little pressure and see if it made a difference.

Basically if 1 and the next place the escapement is cut out (1/25 on the Seikosha) are accurate, then the escapement is properly positioned. And then the pin is used to get 1/10 accurate and see how other speeds fall. After that you can started swedging or filing the speed am to finesse but I wouldn't suggest bothering too much. Most likelt speeds will fall pretty good if you get 1 second and 1/10. Be prepared for 1/10 to jump to 1/192- it's a touchy little bastard when it comes to that pin.

dxqcanada · Jul 5, 2023

To add to Dan's post ... red arrow pallet .... green arrow retard

OAPOli · Jul 5, 2023

ic-racer said:
The fast speeds are too slow, in that case how are you measuring? They may be OK, depending on how you measured.

I'm using an Arduino laser module. Most fast and slow speeds are slow.

OAPOli · Jul 5, 2023

250swb said:
The Fresnel side (the matt side) faces down towards the mirror. As for lubing anything without knowing that simple fact and I wonder what damage you may have done. It's very easy for oil to migrate from the shutter mechanism to the shutter blades and then you get a sticky shutter. Fingers crossed you didn't apply too much lube.

It wouldn't be the first time I fubared something. I used lube very sparingly and there was a definite improvement, so far (touching wood). I figured the grooves would face the ground glass but given there was no noticeable difference in focusing I wanted to double-check.

OAPOli · Jul 5, 2023

Dan Daniel said:
Oh, ok, then the speed pin can be bent. When you cock the shutter, a small arm swings out (or in?? sorry, bad memory- the speed cam is stepped on either the inner edge or outer edge, the arm with the small pin swings to rest against the speed cam). The pin is a medium gray metal. Take a pair of needle nose pliers and bend it towards the speed cam steps. It will be hard to grab hold of, and bending is a gentle slow operation, meaning give a little pressure and see if it made a difference.

Basically if 1 and the next place the escapement is cut out (1/25 on the Seikosha) are accurate, then the escapement is properly positioned. And then the pin is used to get 1/10 accurate and see how other speeds fall. After that you can started swedging or filing the speed am to finesse but I wouldn't suggest bothering too much. Most likelt speeds will fall pretty good if you get 1 second and 1/10. Be prepared for 1/10 to jump to 1/192- it's a touchy little bastard when it comes to that pin.

Thanks for that. Similar to the Synchro-Compur on the Rolleis. We're taking about that circled pin correct? Pic courtesy of @dxqcanada

dxqcanada · Jul 5, 2023

I think that one in red is for the self timer.
The one at 6:30 connects the retard to the speed cam which operates the higher speeds.
The pallet at 4:00 operates the slow speeds.

Dan Daniel · Jul 5, 2023

Yes, it is a little stub but a light grab and pressure bending in or out will affect things

OAPOli · Jul 5, 2023

Ok I had figured it was this one. Couldn't get it to move at all. I'll try again tomorrow.

I did a bit more testing and the 1/25s is a bit unstable and goes down one stop once in a while... (same with 1/50).

dxqcanada · Jul 5, 2023

You first have to start with clean shutter blades ... I've been there, done that.

albada · Jul 6, 2023

OAPOli said:
Ok I had figured it was this one. Couldn't get it to move at all. I'll try again tomorrow.

I did a bit more testing and the 1/25s is a bit unstable and goes down one stop once in a while... (same with 1/50).

Are you saying that the speeds of 1/25 and 1/50 are inconsistent?
If so, after cocking the shutter, it's likely that the hairspring on the escapement is not unwinding the mechanism completely. There are two possible causes of this failure: (1) gummy escapement, or (2) during repair, the sector gear was completely disengaged from the pallet gear, and now they're out of sync.

Mark

OAPOli · Jul 6, 2023

albada said:
Are you saying that the speeds of 1/25 and 1/50 are inconsistent?
If so, after cocking the shutter, it's likely that the hairspring on the escapement is not unwinding the mechanism completely. There are two possible causes of this failure: (1) gummy escapement, or (2) during repair, the sector gear was completely disengaged from the pallet gear, and now they're out of sync.

Mark

Yes! The assembly came out of sync when I cleaned it. I followed the instructions from the Compur Rapid (looks identical to the Seikosha MX/MXL) repair manual to put it back together. The shutter is now is a decent state with only the 1/500 off by over one stop. Thanks all.

dxqcanada · Jul 6, 2023

Great to hear you got it ... I have had many leaf shutters with a weak high speed spring. They get too compressed over time, especially if the shutter gets parked on 1/500 for a long time.

Minolta Autocord shutter and Fresnel

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