SRT101 stuck mirror.

[little-infinity]

Hello people! Lovely forum you have here

I have an Minolta SRT101 from the 1960s. I can tell it's the early model (probably from the first batch) because of the serial number starting with 125xxxx. It's a beautiful camera, and I'm glad I have it at such a young age. From what I can tell hasn't been in repair once. The mirror damper and seals are still there and appear to be in great shape. This thing literally feels like it's gonna last longer than I am. That said there's been some issues recently.

First off, I have 4 lenses that go with this thing.

58mm MC-Rokkor-PF f1.4 (the classic one with silver aperture)
50mm MD Rokkor F2 (a backup lens from a newer SRT100x/200 that I had)
28mm MC-CPC F2.8 (not a rokkor but works fine)
200mm MC-Rokkor-QF F3.5 (again classic with silver aperture)

The SRT101 has been firing off perfectly for quite some time now. Problem is over time, the 58mm has developed a sticky/stiff focusing issue that makes focusing a royal pain. The ring occasionally slips when i focus away from infinity. To make matters worse, my mirror now refuses to return once I trip the shutter. Mirror lockup also fails to return. The thing is this ONLY happens with this lens on. The mirror only returns when I remove the 58mm lens, or sometimes when i turn the focus ring.

I tested with the other 3 lenses and mirror and lockup return works flawlessly.

So I doubt it's the camera (although the MC coupling ring on the mount has also started to stick causing a slight delay in metering whenever i increase aperture but i figure some lube should solve that), and more the lens. Can anyone back me up on this?

What should I do?

 

[Andrew K]

does the 58mm lens focus to infinity?

It sounds like there is something up with this lens that is causing the mirror to physically jam with the lens in place..

I would either service the lens, or just use your other 50mm lens....

I've never had this problem with any of the 8 or 10 SR and SRT series Minoltas I've owned...

 

[elekm]

I would also check the suspect lens to see if the aperture opens and closes in a snappy manner.

If the aperture is sluggish, perhaps it's interfering with the mirror.

And in any case, it sounds as if that lens should be serviced (cleaned and relubricated).

 

[Christopher Walrath]

I would also make certain that the back elements are not in the way of the mirror's travel. Highly unlikely as this problems has recently appeared. If this were the case it would have always happened. Just brainstroming here.

Has the lens been dropped?

 

[little-infinity]

Not that I know of. It's a mighty old lens from my research though. I assume it's the very one that was sold with the SRT101 as a kit (I wish today's SLR kits were that good!). I know a place in Port Credit that will do repairs on site. I'll go get an estimate.

Andrew: From what I can tell, it does, but it gets kinda stuck just BEFORE infinity. One has to put even more force to get it into infinity. I dont try to focus the lens now. The mirror isn't hitting the lens or i would have heard it crack or something. It just doesn't return with that specific lens mounted which is a pity. The moment i push the lens release pin it goes back to normal. I can deal with it but it's rather a nuisance. The optics look clean as a bell.

Mike: Not sure what you mean by sluggish/snappy. Aperture appears to work flawlessly clicking at all stops, DOF preview works too! It stops down at all speeds.

The only plausble explanation is that the sticky focusing has caused the lens' rear element to go awry, and the camera *thinks* the mirror might hit it. How this is so beats me, as this camera doesn't really have a brain! Perhaps the needs a focus calibration? I am totally baffled. Focus looks okay in the viewfinder, but it's hard to tell.

So is my best option to get it checked? I hope the lens isn't a kicker.

 

[upnorthcyclist]

Well, here's a thought. When you look into the front of the camera, with the lens removed, in the bottom of the socket there is a triangular-shaped lever that, when the shutter is actuated, moves back and forth to actuate the lens diaphragm from full open to whatever the lens aperture is set at.

In the chain of things that happen when an exposure is made, I think that lever has to get back to home position for the mirror to then return to the lowered position. In the way it works, if the diaphragm of the lens sticks, the lever will still return, simply leaving the diaphragm wherever it is stuck. But, perhaps, if the pin in the lens that the lever actates was actually interfering with the lever by not going into the camera body deep enough, so that the lever gets behind the pin instead of alongside it, this could stop the sequence. Pushing the lens release button maybe lets the lens move enough to allow the lever to return fully.

This is the only scenario that comes to my mind that could cause the problem you describe with just the one lens. There'd be lots of possibilities if it happened all the time. There're a number of Minolta forums around where you might get some more specific expertise.

Mike

 

[little-infinity]

OOOH now that's an idea!

I'll go take a look. I also notice when mounting this lens, it's alot stiffer than my other lenses (IE harder to turn and lock into the mount). I thought this was a symptom of low usage, but could it mean something else?

Regardless, thanks for the tip!

 

[little-infinity]

Alrighty. Sorry for the double post (not sure if this is allowed) but it turns out you were right. The lens DOESNT focus to infinity. It reaches what appears to be "infinity" at 5m.

I'm guessing all this lens needs is a simple lube and focus adjustment and I'm set? Or is it dead?

 

[Nicholas Lindan]

Alrighty. Sorry for the double post (not sure if this is allowed) but it turns out you were right. The lens DOESNT focus to infinity. It reaches what appears to be "infinity" at 5m.

So it is the back element of the lens interfering with mirror travel. When you crank the lens in past infinity/"5m" the back part of the lens goes farther into the mirror box of the camera -- the mirror then hits the back of the lens and sticks, the slightest movement unsticks the mirror and it returns. The lens need only interfere with the mirror by a few thousands of an inch so there needn't be any great sound of crashing mirrors and grinding gears. The mirror rotates on a springy zero-lash pivot that will allow it to move back an ooch as it hits the back of the lens.

The problem arises because someone before you took the lens apart and either put it back with the focusing helical in the wrong set of grooves or lost the infinity-stop pin.

The reasons the lens may have had an attempted DIY servicing are oil on the diaphragm blades/sticky diaphragm, dried grease in the focusing helical or dirt/clouding/fungus on the interior lens elements.

Get the lens serviced by a reputable shop. Ask on APUG for the name of shops in your area or for mail-order repair outfits that service Minoltas. The repair is generic, though, and any serviceperson should be able to fix it.

 

[upnorthcyclist]

Hi again - I'm having a slow day, so I'll join you in the double-post.

Take a good look at the flange end of your lens and see if there is obvious damage - bent pin, mechanism pushed inwards etc. I suspect perhaps the thing was dropped as what you're describing doesn't sound anything like normal wear. See if you can actuate the diaphragm with the pin - set the lens at minimum aperture and see if it opens and closes nice and snappy.

My experience has been that lens repairs are very expensive - not really any such thing as a simple lube and adjust, like a camera body. You gotta really love a lens, or the lens has to have considerable value to have it reworked by a professional.

The MC 58mm 1.4 is a fine lens, but it isn't one of the Minolta to-die-for collectibles. They made a lot of them. You may be further ahead to keep an eye on the bay for a nice example that doesn't have any problems than to pursue getting this one fixed.

Mike

 

[upnorthcyclist]

Nicholas - you may have it - I was writing my reply when you posted yours. That would, indeed 'splain everything.

Mike

 

[John Koehrer]

Check focus at infinity with a ground glass on the film rails. If the focus is off at infinity it's off at close distances too.
If the lens won't focus to infinity, that suggests two possible faults.
1)the simplest is the focusing ring has slipped. Remove the decorator ring and under it there should be three screws. Adjust the lens to infinity, loosen the screws and move the focusing ring to the infinity stop. It should move freely, tighten the screws.
2)If the helical is off a thread, It's easier to do than describe, but the mount has to be removed, focus ring removed, stop down lever and spring removed, then the hard part. Unscrew the helical and move it one thread either direction. It'll get better or worse. Better? leave it alone. Worse? Move it two threads in the opposite direction & put all the stuff back in place.

 

[little-infinity]

Hmm. Sounds like that's the issue!

Still find it a tad odd that the mirror can go up, but not down if the element was protruding back. You'd think it wouldn't work both ways.

I think I'll get the lens fixed though. I like the feel of it. I'm lucky enough that I have a good place that does pro repairs on site just down the street from where I live. I'll get an estimate to see if its worth it.