SMC Takumar 50 f1.4 Clutch Problem

TheRealMrBlue · 01-04-2019, 11:50 PM

Tried to post in the repair forum, got a message saying no new posts allowed there so trying here.

My SMC Tak 50mm f1.4 has an issue with the clutch. Typically, the clutch shouldn't allow switching from Man > Auto unless the secondary flange pin is depressed. On my Tak, the clutch level moves even if the lens is not mounted. I noticed that the aperture pin doesn't pop up, but will come out normally if I invert the lens (rear element down).

It appears as if the spring that pushes the pin out is either not engaged or is missing?

Is there a way to fix/troubleshoot this without completely tearing down the lens?

Not a Number · 01-05-2019, 03:30 AM

Does the A/M switch lock when the pin is out?

You're going to have to open the lens up to see what's going on, but you probably won't have to completely tear it down.

If the iris stops down or opens when you operate the A/M switch does it really matter if the clutch pin works or not?

The third party lenses (i.e. Vivitar) that I have with A/M switches do not have a clutch pin.

**aslyfox** · 01-05-2019, 04:57 AM

are you aware of JIS screws ?
you may want to review this thread before starting -

Cross-head screws - a caution: - PentaxForums.com

Not a Number · 01-05-2019, 05:55 AM

Originally posted by aslyfox

are you aware of JIS screws ?
you may want to review this thread before starting -

Cross-head screws - a caution: - PentaxForums.com

All the Takumars and early Minolta Rokkor lenses with the all metal focus rings I have use slotted screws (vs cross head). They were manufactured before the Japanese Optical and Photography manufacturers adopted JIS which was late 60'-early 70's.

But buying a set of JIS drivers is good advice for DIY repairs on lenses that use cross head screws.

**aslyfox** · 01-05-2019, 05:57 AM

Originally posted by Not a Number

All the Takumars and early Minolta Rokkor lenses with the all metal focus rings I have use slotted screws (vs cross head). They were manufactured before the Japanese Optical and Photography manufacturers adopted JIS which was late 60'-early 70's. . . .

that is knowledge I didn't have, thanks

**simple1** · 01-05-2019, 12:25 PM

Assuming it's like the Tak 55/1.8 you'll have to open the lens up.

The spring is just a piece of spring steel held down by a screw. Possibly the screw was loose and the spring rotated.

Here is the spring in place.

And here is with the spring removed.

TheRealMrBlue · 01-05-2019, 01:46 PM

Originally posted by Not a Number

Does the A/M switch lock when the pin is out?

You're going to have to open the lens up to see what's going on, but you probably won't have to completely tear it down.

If the iris stops down or opens when you operate the A/M switch does it really matter if the clutch pin works or not?

The third party lenses (i.e. Vivitar) that I have with A/M switches do not have a clutch pin.

Yes. The switch moves when the pin is out.

The iris works fine, my primary wish was simply to be able to take advantage of the open metering on my Spotmatic F.

**.a.t.** · 01-07-2019, 11:44 AM

Originally posted by simple1

Assuming it's like the Tak 55/1.8 you'll have to open the lens up...

The pictures are helpful. Thanks, simple1.

Not a Number · 01-07-2019, 02:26 PM

My mistake, I thought you were talking about the secondary pin on the flange. I would call that a clutch pin because it engages or disengages the movement of the A/M switch. I call the longer pin the aperture stop-down pin.

So you're saying the iris will not default to open in the auto mode? The problem could be in the A/M switch as well.

TheRealMrBlue · 01-07-2019, 05:56 PM

The lens is in manual all the time, regardless of the switch position. In effect, I cannot switch it to auto since the blades close/open whenever I rotate the aperture ring.

The longer aperture pin just "floats" in its hole as if the spring underneath it is missing.

I can live with it as is but like I said earlier, I'd like to take advantage of the ability to meter while open.

I'm quite handy, but I don't quite have the confidence to tackle this particular job.

**simple1** · 01-08-2019, 06:03 AM

Originally posted by .a.t.

The pictures are helpful. Thanks, simple1.

Glad it was helpful.

I noticed the pictures were gone in the Tak 55/1.8 repair thread, when I get a chance maybe I’ll write another.

TheRealMrBlue · 04-01-2020, 11:48 PM

Took the plunge and fixing this was much easier than I had anticipated. Thanks to everyone that provided feedback!

01-04-2019, 11:50 PM	#1
TheRealMrBlue New Member Join Date: May 2018 Photos: Gallery \| Albums Posts: 10	SMC Takumar 50 f1.4 Clutch Problem Tried to post in the repair forum, got a message saying no new posts allowed there so trying here. My SMC Tak 50mm f1.4 has an issue with the clutch. Typically, the clutch shouldn't allow switching from Man > Auto unless the secondary flange pin is depressed. On my Tak, the clutch level moves even if the lens is not mounted. I noticed that the aperture pin doesn't pop up, but will come out normally if I invert the lens (rear element down). It appears as if the spring that pushes the pin out is either not engaged or is missing? Is there a way to fix/troubleshoot this without completely tearing down the lens?

01-05-2019, 03:30 AM	#2
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	Does the A/M switch lock when the pin is out? You're going to have to open the lens up to see what's going on, but you probably won't have to completely tear it down. If the iris stops down or opens when you operate the A/M switch does it really matter if the clutch pin works or not? The third party lenses (i.e. Vivitar) that I have with A/M switches do not have a clutch pin. Last edited by Not a Number; 01-05-2019 at 03:37 AM.

01-05-2019, 12:25 PM	#6
simple1 Loyal Site Supporter Join Date: Dec 2009 Location: In the Florida swamps Posts: 764	Assuming it's like the Tak 55/1.8 you'll have to open the lens up. The spring is just a piece of spring steel held down by a screw. Possibly the screw was loose and the spring rotated. Here is the spring in place. And here is with the spring removed. Last edited by simple1; 01-05-2019 at 12:33 PM.

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01-05-2019, 04:57 AM	#3
aslyfox Seeker of Knowledge Join Date: Aug 2016 Location: Topeka, Kansas Photos: Gallery \| Albums Posts: 24,581	are you aware of JIS screws ? you may want to review this thread before starting - Cross-head screws - a caution: - PentaxForums.com

01-05-2019, 05:55 AM	#4
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	Originally posted by aslyfox are you aware of JIS screws ? you may want to review this thread before starting - Cross-head screws - a caution: - PentaxForums.com All the Takumars and early Minolta Rokkor lenses with the all metal focus rings I have use slotted screws (vs cross head). They were manufactured before the Japanese Optical and Photography manufacturers adopted JIS which was late 60'-early 70's. But buying a set of JIS drivers is good advice for DIY repairs on lenses that use cross head screws.

01-05-2019, 05:57 AM	#5
aslyfox Seeker of Knowledge Join Date: Aug 2016 Location: Topeka, Kansas Photos: Gallery \| Albums Posts: 24,581	Originally posted by Not a Number All the Takumars and early Minolta Rokkor lenses with the all metal focus rings I have use slotted screws (vs cross head). They were manufactured before the Japanese Optical and Photography manufacturers adopted JIS which was late 60'-early 70's. . . . that is knowledge I didn't have, thanks

01-05-2019, 01:46 PM	#7
TheRealMrBlue New Member Join Date: May 2018 Photos: Gallery \| Albums Posts: 10 Original Poster	Originally posted by Not a Number Does the A/M switch lock when the pin is out? You're going to have to open the lens up to see what's going on, but you probably won't have to completely tear it down. If the iris stops down or opens when you operate the A/M switch does it really matter if the clutch pin works or not? The third party lenses (i.e. Vivitar) that I have with A/M switches do not have a clutch pin. Yes. The switch moves when the pin is out. The iris works fine, my primary wish was simply to be able to take advantage of the open metering on my Spotmatic F.

01-07-2019, 11:44 AM	#8
.a.t. Site Supporter Join Date: Mar 2011 Location: yesterday Photos: Gallery Posts: 1,261	Originally posted by simple1 Assuming it's like the Tak 55/1.8 you'll have to open the lens up... The pictures are helpful. Thanks, simple1.

01-07-2019, 02:26 PM	#9
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	My mistake, I thought you were talking about the secondary pin on the flange. I would call that a clutch pin because it engages or disengages the movement of the A/M switch. I call the longer pin the aperture stop-down pin. So you're saying the iris will not default to open in the auto mode? The problem could be in the A/M switch as well.

01-07-2019, 05:56 PM	#10
TheRealMrBlue New Member Join Date: May 2018 Photos: Gallery \| Albums Posts: 10 Original Poster	The lens is in manual all the time, regardless of the switch position. In effect, I cannot switch it to auto since the blades close/open whenever I rotate the aperture ring. The longer aperture pin just "floats" in its hole as if the spring underneath it is missing. I can live with it as is but like I said earlier, I'd like to take advantage of the ability to meter while open. I'm quite handy, but I don't quite have the confidence to tackle this particular job.

01-08-2019, 06:03 AM	#11
simple1 Loyal Site Supporter Join Date: Dec 2009 Location: In the Florida swamps Posts: 764	Originally posted by .a.t. The pictures are helpful. Thanks, simple1. Glad it was helpful. I noticed the pictures were gone in the Tak 55/1.8 repair thread, when I get a chance maybe I’ll write another.

04-01-2020, 11:48 PM	#12
TheRealMrBlue New Member Join Date: May 2018 Photos: Gallery \| Albums Posts: 10 Original Poster	Took the plunge and fixing this was much easier than I had anticipated. Thanks to everyone that provided feedback!