Pentax 70-210 zoom push stuck!

automorphism · 06-03-2020, 07:45 PM

So, I have Pentax-A 70-210mm f/4 manual lens. Got it for about $50.

I don't use it much, except for experimenting with reverse-lens macro -- I attach a 50mm lens reversed onto it with a reverse-lens ring to get up to about 4x macro. Not really great resolution, but sometimes it can work.

Anyway, this 70-210 has a push-pull for zooming. Now it seems to be stuck at 200-210mm. It moves a little but that's it. Anyone have any idea how to fix this thing? I don't mind taking it apart as it was so cheap anyway.

bdery · 06-04-2020, 05:11 AM

I suggest looking to find repair manuals online, you might get lucky.

Each lens is different, even though there are similarities. I suggest, if you attempt it, to document and photograph each step you take, so as to avoid mistakes when putting it back together.

D1N0 · 06-04-2020, 05:32 AM

Have you tried the entire focal range? It has a macro mode at 70mm. When it is in there it also cannot zoom. Albeit at the other end of the zoom range.

**gofour3** · 06-04-2020, 07:19 AM

As mentioned above, my guess is that your zoom is stuck in the macro position.

This is a page from the A Series lens manual on how to free it.

Phil.

Attached Images

automorphism · 06-04-2020, 07:23 AM

Originally posted by D1N0

Have you tried the entire focal range? It has a macro mode at 70mm. When it is in there it also cannot zoom. Albeit at the other end of the zoom range.

The problem is, I cannot move it to 70mm. It only moves between 200-210. Based on your comment I thought maybe that limiter was holding it in place so I tried twisting it but to no avail.

I might try taking it apart sometime today and see what's going on with it.

Not a Number · 06-04-2020, 05:06 PM

Zooms from the era that this was built often have plastic cams in guide slots to control the zoom action. These cams break or get flat wear spots. In which case they should be replaced. Other than a donor lens there probably is not a source for parts. Perhaps they could be 3D printed though.

Let us know what you find.

j0n4hpk · 06-04-2020, 05:53 PM

Thanks for this thread, friends. I have a similar problem with the same kind of lens and will attempt some of your suggestions as soon as I can get from my 'off-site" storage. Keep suggestions coming...

06-03-2020, 07:45 PM	#1
automorphism Veteran Member Join Date: Jun 2015 Location: Ontario, Canada Photos: Albums Posts: 791	Pentax 70-210 zoom push stuck! So, I have Pentax-A 70-210mm f/4 manual lens. Got it for about $50. I don't use it much, except for experimenting with reverse-lens macro -- I attach a 50mm lens reversed onto it with a reverse-lens ring to get up to about 4x macro. Not really great resolution, but sometimes it can work. Anyway, this 70-210 has a push-pull for zooming. Now it seems to be stuck at 200-210mm. It moves a little but that's it. Anyone have any idea how to fix this thing? I don't mind taking it apart as it was so cheap anyway.

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06-04-2020, 05:11 AM	#2
bdery Pentaxian Join Date: Mar 2008 Location: Quebec city, Canada Photos: Gallery Posts: 9,357	I suggest looking to find repair manuals online, you might get lucky. Each lens is different, even though there are similarities. I suggest, if you attempt it, to document and photograph each step you take, so as to avoid mistakes when putting it back together.

06-04-2020, 05:32 AM	#3
D1N0 Pentaxian Join Date: May 2012 Location: --- Photos: Gallery Posts: 6,802	Have you tried the entire focal range? It has a macro mode at 70mm. When it is in there it also cannot zoom. Albeit at the other end of the zoom range.

06-04-2020, 07:19 AM	#4
gofour3 Site Supporter Join Date: Oct 2008 Location: Vancouver, Canada Posts: 8,091	As mentioned above, my guess is that your zoom is stuck in the macro position. This is a page from the A Series lens manual on how to free it. Phil. Attached Images

06-04-2020, 07:23 AM	#5
automorphism Veteran Member Join Date: Jun 2015 Location: Ontario, Canada Photos: Albums Posts: 791 Original Poster	Originally posted by D1N0 Have you tried the entire focal range? It has a macro mode at 70mm. When it is in there it also cannot zoom. Albeit at the other end of the zoom range. The problem is, I cannot move it to 70mm. It only moves between 200-210. Based on your comment I thought maybe that limiter was holding it in place so I tried twisting it but to no avail. I might try taking it apart sometime today and see what's going on with it.

06-04-2020, 05:06 PM	#6
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	Zooms from the era that this was built often have plastic cams in guide slots to control the zoom action. These cams break or get flat wear spots. In which case they should be replaced. Other than a donor lens there probably is not a source for parts. Perhaps they could be 3D printed though. Let us know what you find.

06-04-2020, 05:53 PM	#7
j0n4hpk Senior Member Join Date: Apr 2009 Location: Ohio Photos: Gallery \| Albums Posts: 293	Thanks for this thread, friends. I have a similar problem with the same kind of lens and will attempt some of your suggestions as soon as I can get from my 'off-site" storage. Keep suggestions coming...