Pentax K 1.8/85 with sluggish aperture blades

huge10 · 01-29-2020, 03:42 PM

Hi,

Finally I acquired a near mint K 1.8 85mm. There is one problem with it: the aperture blades rather sluggish. There is no oil on the blades. I recently did a succefull repair on an A-version 2.8/135mm with sluggish blades and now want to get into the 85mm. I didn't find any information or instructions on how to disassemble this lens for cleaning out the diaphragm mechanism. There is only one thread here in the forum where it is strongly advised to leave it over to a repair specialist, because of the value of the lens. But I trust I will be able to finish this succesfully with some help.

So, who can lead me to good info on disassembling this lens? Is this the standard procedure (removing the front ring, etc,), or is the only way to remove the bayonet mount, etc.? I might try, but prefer to go the right way from the start.

Your help will be much appreciated.

Regards, Wim

stevebrot · 01-30-2020, 11:29 AM - **2 Likes**

Unless you are experienced with lens repair and given the value of the lens, you might want to consider a professional service to address this problem.

Steve

**gofour3** · 01-30-2020, 01:52 PM - **1 Like**

I had a similar issue with my K85/1.8 and it did turn out to be oil on the aperture blades. I sent it to Eric for a CLA and it's perfect now.

I agree with Steve and would send it in for a CLA.

Phil.

**Just1MoreDave** · 01-30-2020, 02:15 PM

My guess is that it's not that complicated inside. My Super Takumar 85mm is pretty much like a Super Takumar 55mm, just bigger. There's no close focus, 18 blade, electronic zoom whatever to worry about. The only problem is that there's no handy guide with photos; you'd be a pioneer. I would pay attention to preserving things like alignment and orientation, even if it might not appear to matter. Just looking at the design of the K series, Pentax intended them to be top of the line, no shortcuts. Don't lose any parts.

People here have made far more complicated gear repairs on the FA* 85.

The really worst case is you have an excuse to buy the DFA 85.

huge10 · 01-31-2020, 01:51 AM

I am sure that it is not too complicated. I have opened (and cleaned/repaired) many Takumars and bayonet lenses, so I know what to expect. In this case I wonder if I have to start from the front by removing the name ring or from the back. It might be that the focusing ring is fixed with srews under the rubber ring. It would be nice to have information on how to disassemble before I start.

Regards, Wim

huge10 · 01-31-2020, 03:23 PM

Originally posted by gofour3

I had a similar issue with my K85/1.8 and it did turn out to be oil on the aperture blades. I sent it to Eric for a CLA and it's perfect now.

I agree with Steve and would send it in for a CLA.

Phil.

As I am in Europe sending it to Eric is no option. Adding to the charge of Eric there is two times shipping cost and probably two times customs charges. No thank you.
BTW: anybody has a clue on what Eric would charge for a CLA of such type of lens?

Regards, Wim

**gofour3** · 01-31-2020, 05:25 PM

Originally posted by huge10

As I am in Europe sending it to Eric is no option. Adding to the charge of Eric there is two times shipping cost and probably two times customs charges. No thank you.
BTW: anybody has a clue on what Eric would charge for a CLA of such type of lens?

It was about $50.00USD if I remember correctly, it was done in 2009 so the prices may have gone up.

Phil.

huge10 · 07-02-2020, 05:58 AM - **5 Likes**

I finally dared to attack the problem. Still not knowing how to enter from the front I did remove the mounting ring. Be aware of threadlocked screws! I start heating the screw had with an adapted soldering iron. Just touch the screw head, while holding the barrel with your thumb. Holding it prevents you from overheating! After two minutes or so the threadlock weakens enough to unscrew rather easy, not damaging the screw head. And don't forget: buy yourself a set of quality JIS screw drivers.
No case of oily aperture blades! Under the mounting ring there is a ring to operate the aperture mechanism. There was some oil on this ring. I just cleaned the ring and the surrounding surfaces. Now everything is fine! From now on I am the lucky owner of a pristine Pentax-K 1.8/85mm lens. Ready for use on my Pentax K1MKII.

I am a proud Pentax tinkerer!

Regards, Wim

**gofour3** · 07-02-2020, 08:28 AM - **1 Like**

Originally posted by huge10

I finally dared to attack the problem. Still not knowing how to enter from the front I did remove the mounting ring. Be aware of threadlocked screws! I start heating the screw had with an adapted soldering iron. Just touch the screw head, while holding the barrel with your thumb. Holding it prevents you from overheating! After two minutes or so the threadlock weakens enough to unscrew rather easy, not damaging the screw head. And don't forget: buy yourself a set of quality JIS screw drivers.
No case of oily aperture blades! Under the mounting ring there is a ring to operate the aperture mechanism. There was some oil on this ring. I just cleaned the ring and the surrounding surfaces. Now everything is fine! From now on I am the lucky owner of a pristine Pentax-K 1.8/85mm lens. Ready for use on my Pentax K1MKII.

I am a proud Pentax tinkerer!

Regards, Wim

Good news and enjoy the lens!

Phil.

01-29-2020, 03:42 PM	#1
huge10 Forum Member Join Date: Mar 2018 Location: Apeldoorn, The Netherlands Posts: 61	Pentax K 1.8/85 with sluggish aperture blades Hi, Finally I acquired a near mint K 1.8 85mm. There is one problem with it: the aperture blades rather sluggish. There is no oil on the blades. I recently did a succefull repair on an A-version 2.8/135mm with sluggish blades and now want to get into the 85mm. I didn't find any information or instructions on how to disassemble this lens for cleaning out the diaphragm mechanism. There is only one thread here in the forum where it is strongly advised to leave it over to a repair specialist, because of the value of the lens. But I trust I will be able to finish this succesfully with some help. So, who can lead me to good info on disassembling this lens? Is this the standard procedure (removing the front ring, etc,), or is the only way to remove the bayonet mount, etc.? I might try, but prefer to go the right way from the start. Your help will be much appreciated. Regards, Wim

07-02-2020, 05:58 AM - 5 Likes	#8
huge10 Forum Member Join Date: Mar 2018 Location: Apeldoorn, The Netherlands Posts: 61 Original Poster	I finally dared to attack the problem. Still not knowing how to enter from the front I did remove the mounting ring. Be aware of threadlocked screws! I start heating the screw had with an adapted soldering iron. Just touch the screw head, while holding the barrel with your thumb. Holding it prevents you from overheating! After two minutes or so the threadlock weakens enough to unscrew rather easy, not damaging the screw head. And don't forget: buy yourself a set of quality JIS screw drivers. No case of oily aperture blades! Under the mounting ring there is a ring to operate the aperture mechanism. There was some oil on this ring. I just cleaned the ring and the surrounding surfaces. Now everything is fine! From now on I am the lucky owner of a pristine Pentax-K 1.8/85mm lens. Ready for use on my Pentax K1MKII. I am a proud Pentax tinkerer! Regards, Wim Last edited by huge10; 07-02-2020 at 06:01 AM. Reason: typos

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01-30-2020, 11:29 AM - 2 Likes	#2
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Unless you are experienced with lens repair and given the value of the lens, you might want to consider a professional service to address this problem. Steve

01-30-2020, 01:52 PM - 1 Like	#3
gofour3 Site Supporter Join Date: Oct 2008 Location: Vancouver, Canada Posts: 8,091	I had a similar issue with my K85/1.8 and it did turn out to be oil on the aperture blades. I sent it to Eric for a CLA and it's perfect now. I agree with Steve and would send it in for a CLA. Phil.

01-30-2020, 02:15 PM	#4
Just1MoreDave Site Supporter Join Date: Feb 2007 Location: Aurora, CO Photos: Gallery \| Albums Posts: 6,340	My guess is that it's not that complicated inside. My Super Takumar 85mm is pretty much like a Super Takumar 55mm, just bigger. There's no close focus, 18 blade, electronic zoom whatever to worry about. The only problem is that there's no handy guide with photos; you'd be a pioneer. I would pay attention to preserving things like alignment and orientation, even if it might not appear to matter. Just looking at the design of the K series, Pentax intended them to be top of the line, no shortcuts. Don't lose any parts. People here have made far more complicated gear repairs on the FA* 85. The really worst case is you have an excuse to buy the DFA 85.

01-31-2020, 01:51 AM	#5
huge10 Forum Member Join Date: Mar 2018 Location: Apeldoorn, The Netherlands Posts: 61 Original Poster	I am sure that it is not too complicated. I have opened (and cleaned/repaired) many Takumars and bayonet lenses, so I know what to expect. In this case I wonder if I have to start from the front by removing the name ring or from the back. It might be that the focusing ring is fixed with srews under the rubber ring. It would be nice to have information on how to disassemble before I start. Regards, Wim

01-31-2020, 03:23 PM	#6
huge10 Forum Member Join Date: Mar 2018 Location: Apeldoorn, The Netherlands Posts: 61 Original Poster	Originally posted by gofour3 I had a similar issue with my K85/1.8 and it did turn out to be oil on the aperture blades. I sent it to Eric for a CLA and it's perfect now. I agree with Steve and would send it in for a CLA. Phil. As I am in Europe sending it to Eric is no option. Adding to the charge of Eric there is two times shipping cost and probably two times customs charges. No thank you. BTW: anybody has a clue on what Eric would charge for a CLA of such type of lens? Regards, Wim

01-31-2020, 05:25 PM	#7
gofour3 Site Supporter Join Date: Oct 2008 Location: Vancouver, Canada Posts: 8,091	Originally posted by huge10 As I am in Europe sending it to Eric is no option. Adding to the charge of Eric there is two times shipping cost and probably two times customs charges. No thank you. BTW: anybody has a clue on what Eric would charge for a CLA of such type of lens? It was about $50.00USD if I remember correctly, it was done in 2009 so the prices may have gone up. Phil.

07-02-2020, 08:28 AM - 1 Like	#9
gofour3 Site Supporter Join Date: Oct 2008 Location: Vancouver, Canada Posts: 8,091	Originally posted by huge10 I finally dared to attack the problem. Still not knowing how to enter from the front I did remove the mounting ring. Be aware of threadlocked screws! I start heating the screw had with an adapted soldering iron. Just touch the screw head, while holding the barrel with your thumb. Holding it prevents you from overheating! After two minutes or so the threadlock weakens enough to unscrew rather easy, not damaging the screw head. And don't forget: buy yourself a set of quality JIS screw drivers. No case of oily aperture blades! Under the mounting ring there is a ring to operate the aperture mechanism. There was some oil on this ring. I just cleaned the ring and the surrounding surfaces. Now everything is fine! From now on I am the lucky owner of a pristine Pentax-K 1.8/85mm lens. Ready for use on my Pentax K1MKII. I am a proud Pentax tinkerer! Regards, Wim Good news and enjoy the lens! Phil.