Pentax S3 lens stop down problem

Chan Tran · Sep 20, 2012

I just got this very clean Pentax S3 and it has a problem. When I put the lens on A the aperture is supposed to stop down to the set aperture before exposure but I found that sometimes it only stops down partly or not at all. The problem is worse if the camera is pointed upward (lens pointing up). The problem is not so much if the lens is pointed downward. At long exposure like 1 sec I could see that the aperture would stop down slowly to the set aperture. The aperture stop down pin on the lens actin feel normal. It doesn't feel tight so I don't think it's the lens. When pointing the camera upward sometimes it gets so bad that the camera could not complete the cycle.
I would greatly appreciate and help on this matter.

E. von Hoegh · Sep 20, 2012

Sticky lens diaphragm.

benjiboy · Sep 20, 2012

Needs a C.L.A.

E. von Hoegh · Sep 20, 2012

Chan, I think pushing the pin on the lens doesn't close the diaphragm, it releases the diaphragm so it can be closed by an internal spring. This is why it doesn't feel tight. Even if it doesn't work the way I think, it would take very little drag to slow things down. When the lens is pointing up, the blades are probably lying on each other and dragging.

Check it with a different lens on that body to be certain it is the lens.

Chan Tran · Sep 20, 2012

E. von Hoegh said:
Chan, I think pushing the pin on the lens doesn't close the diaphragm, it releases the diaphragm so it can be closed by an internal spring. This is why it doesn't feel tight. Even if it doesn't work the way I think, it would take very little drag to slow things down. When the lens is pointing up, the blades are probably lying on each other and dragging.

Check it with a different lens on that body to be certain it is the lens.

This is the screw mount lens exactly it's the Auto Takuma 55mm f/1.8. Pushing the pin IN close the aperture when the stop down switch on the lens is set at A. When it's set at M the lens is always stopped down to the set aperture. Not like the new Pentax K mount that letting go of the level close the aperture.

Jerevan · Sep 20, 2012

Send it off to Eric at www.pentaxs.com - he does a good job. It could be a combination of the lens and the body needing CLA, as it was in my case (Pentax S1a).

Bill Burk · Sep 20, 2012

Just take the lens off the camera and push the pin in. You'll see soon enough if the lens is the issue.

p.s. I had the Spotmatic F w/50mm f/1.4 around my neck while reading this so all I had to do was take off the lens and try it myself...

Chan Tran · Sep 20, 2012

Bill Burk said:
Just take the lens off the camera and push the pin in. You'll see soon enough if the lens is the issue.

p.s. I had the Spotmatic F w/50mm f/1.4 around my neck while reading this so all I had to do was take off the lens and try it myself...

Like I said in the first post, taking the lens out and pushing the pin it works with little resistance. It seems that the camera spring doesn't supply enough force to push the pin.

Yashinoff · Sep 20, 2012

Yes but does the lens stop down when you push the pin? Or does it stick?

And if it does stop down, then have you checked the function of the diaphragm plunger in the camera? Is it slow or sticking?

Chan Tran · Sep 20, 2012

The lens stop down with very light pressure on the pin when I had it out of the camera. The diaphram doesn't look oily. However, when the lens is out the pusher plate move quickly and doesn't seem to have a problem.

Yashinoff · Sep 20, 2012

Chan Tran said:
The lens stop down with very light pressure on the pin when I had it out of the camera. The diaphram doesn't look oily. However, when the lens is out the pusher plate move quickly and doesn't seem to have a problem.

If you have the camera on you, open the back, set the shutter to B and fire/open the shutter so you can observe the plunger and pin from the inside. I had a problem with an Edixa where the pin was getting stuck between the plunger the bottom of the lens throat, I was able to see it happen by doing this.

Chan Tran · Sep 20, 2012

Yashinoff said:
If you have the camera on you, open the back, set the shutter to B and fire/open the shutter so you can observe the plunger and pin from the inside. I had a problem with an Edixa where the pin was getting stuck between the plunger the bottom of the lens throat, I was able to see it happen by doing this.

There is no such pin when open the back of the camera. There is a bar that push the pin. This bar is pushed by a level. This level is mounted on the side of the mirror box but it can not be seen unless disassembled.

Yashinoff · Sep 20, 2012

Chan Tran said:
There is no such pin when open the back of the camera. There is a bar that push the pin. This bar is pushed by a level. This level is mounted on the side of the mirror box but it can not be seen unless disassembled.

I'm saying that you should be able to see the plunger in the camera, pushing the pin on the lens, if you looking in through the gate in the film plane when the shutter is open. If the plunger is not pushing all the way out against the pin, you should be able to see it.

Bill Burk · Sep 20, 2012

Chan Tran said:
There is no such pin when open the back of the camera. There is a bar that push the pin. This bar is pushed by a level. This level is mounted on the side of the mirror box but it can not be seen unless disassembled.

Funny, went to check and my rewind knob was missing. Be sure to cinch that down tight or it might fall off. Retraced my steps, went back where I was walking today and found the knob.

Now for your problem. With the lens off, inspect the bar that presses the pin when the shutter is activated. S3 does not have a meter switch, been a while since I had an S3V. The bar might be different than my Spotmatic F. On mine the bar is bent back on left and right sides so you can remove the lens or attach it and it won't shear the pin as you screw the lens on.

Check the shape of the bar and make sure it does not catch on anything. Maybe it's a little bent and hits the inside of the lens mount instead of moving forward freely all the way?

Good luck solving the problem.

Chan Tran · Sep 21, 2012

Thanks Bill and all! I removed the front of the camera. Put a little oil in the level. It works ok now but I doubt it will be for long. I checked the shutter speed and it's all over the place. I think I will get rid of it although it's a very clean and nice looking camera. I hang on to my trusty KX.

Pentax S3 lens stop down problem

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