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05-07-2015, 11:40 AM   #1
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Need some Tech Help with 67 500mm f5.6 Lens

Hi Everyone

This is my 1st Post but I've been reading & viewing this Wonderful Pentax Forum for sometime . . . My Pentax Cameras include a K10D, K5iis & Q7 . . . Lots of Fun !

I very recently purchased an Older SMC Pentax 6x7 500mm f:5.6 Lens and it was operational for about 3-weeks BEFORE an internal Stop / Glide Bracket came loose & allowed the Lens to Twist Apart into it's (2) Main Assemblies . . .

Here's some Photos that Show What's Going On and & I've Managed to Acquire (2) Replace Screws ( That were Missing ) so it Doesn't look like I need any parts . . . All is Well NOW, I just have to Learn How to Put it Back Together !

The MAIN THING I NEED HELP WITH is . . . I'm Not Sure of the Correct Sequence of Dis-Assembly & Re-Assembly . . .
The Lens was Not Designed to Be Able to Completely Un-Screw when Trying to Focus the Lens ( The Stop / Glide Brackets NORMALLY Stop that from Happening ) I Spotted & Fixed the Problem ( 2 ) Missing Bracket Holding Screws

I haven't been able to locate any Service Manuals or ANY Specific Information on the Sequence of Assembly or If any Unusual Tools are Required . . . Any Help will be Greatly Appreciated !

Just would like a Little Experienced Guidance on how to safely proceed . . . I really like this Old SMC Pentax 6x7 500mm f:5.6 Lens & want to get it Back in the Game !

Many Thanks & Cheers from Orion12

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05-07-2015, 01:55 PM   #2
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In order to reassemble it, you are going to need to first remove the pieces that you call "glide brackets" as well as the rear mount of the lens. You will then have to re-thread the side of the helical that has come off track. once you have the helical rethreaded, you are going to thread it all the way in as far as it can go, set the focus to infinity, and then align to the two sides of the helical so you can re-attach the brackets.

The difficulty is going to be that the helical thread has multiple entry points, so you won't necessarily end up in the correct one on the first try. You can either try the different entry points, or if you can locate the screws that hold the outer focus ring to the internal ones, you can loosen simply them, get the reassembled lens focused to infinity, and then tighten them down with the focus ring in the correct spot. I've not worked on this lens before, but you might be able to access these screws under the grip or from the front of the lens. The stops on the outer focus ring are what will keep the helical from threading out far enough to disengage if you have the brackets in place correctly. The bracket ssimply coordinate the movement between the outer and inner helical rings.

When you put the ount back on, take care to make sure all of the aperture linkages are engaging correctly.

Last edited by dcshooter; 05-07-2015 at 02:03 PM.
05-07-2015, 05:01 PM   #3
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Thanks DcShooter . . . I appreciate your help . . .

I added a Note and Updated Photo as it Better Explains what the Challenge is . . . It LOOKS LIKE I should Remove the Rear Flange Plate to Gain Access to the Internals . . . Including Being Able to Tighten the Glide Bracket once the (2) Primary Assemblies are Together . . . You are correct about NOT Being able to Screw the Parts Together WITH the Brackets in Final Position BUT If simply Screwed Together the Rear Lens Tube BLOCKS Access to Being able to Tighten the Glide Brackets . . . Please let me know any Insights you have . . . This is the 1st 67 Series Lens I've had to do any Mechanical's on . . . Major Thanks & Cheers from Orion12
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05-07-2015, 10:14 PM   #4
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If you get stuck email Eric:

Pentax Camera Service


Phil.

05-08-2015, 03:29 AM   #5
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Thanks Phil . . .

I'll take it up a Notch & Inspect the Internals by Removing the Rear Flange Plate . . .
Hopefully it will be Obvious how to Proceed . . .
If this Approach FAILS . . . I'll Definitely Email Eric . . . I really appreciate the Tip as I wouldn't have Known the Next Step.

Cheers from Orion12
05-08-2015, 09:31 AM   #6
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Here's what the Rear Lens Flange looks like . . . Are these Standard Phillips Head Screws ?

Thanks & Cheers from Orion12
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05-08-2015, 10:27 AM   #7
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JIS screws. They have a different head angle than Philips. Be very careful if you attempt to remove them with a Philips driver, since it is very easy to strip out the head.

Moody Tools sells a set of micro JIS drivers for under 25 bucks that will be much safer to use:

http://www.amazon.com/Moody-Tools-Driver-Pollicis-55-0318/dp/B002R87ZDI/ref=...y+pollicis+jis
05-08-2015, 10:50 AM   #8
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QuoteOriginally posted by dcshooter Quote
JIS screws. They have a different head angle than Philips. Be very careful if you attempt to remove them with a Philips driver, since it is very easy to strip out the head.

Moody Tools sells a set of micro JIS drivers for under 25 bucks that will be much safer to use:

http://www.amazon.com/Moody-Tools-Driver-Pollicis-55-0318/dp/B002R87ZDI/ref=...y+pollicis+jis
Hi DcShooter . . . I discovered that a few minutes After Writing Last Posts . . . Just Ordered as Set of JIS Type S Moody ScrewDrivers from Amazon ( I Liked Your Selection Better However / Should have Looked Here 1st lol ) . . .
Thanks Tons for Noticing & Getting Me a Message . . .

Major Cheers from Orion

05-08-2015, 01:09 PM   #9
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My pleasure. All of the Moody screwdrivers are excellent, so I'm sure you'll be happy with what you get. They are the only brand I use, and they make a huge difference.

One other tip: If the screws are very tight, as sometimes happens with Pentax mount screws, try putting a drop of acetone or MEK on them prior to unscrewing them in case they have had threadlocker applied. If they still won't budge, heating for 30 seconds with the tip of a soldering iron can help, too.
05-08-2015, 06:53 PM   #10
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Super Thanks for the Acetone / MEK Tip + Soldering Gun Heat IF Needed . . . Pretty Sure these Screws are in Pretty Tight ! So will Likely Need All the Tricks Available BEFORE the Trumpets Sound ! ( Hopefully this will be the Case )

More Cheers from Orion
05-24-2015, 05:51 PM   #11
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Hi Phil & DcShooter ,

I received the JIS ( Moody ) Screw Driver Set ( Thanks Again ) Got ALL the Rear Plate & Other Related Screw OUT ( Awesome to have the Right Tools ) . . .

BUT As the New Photos SHOW . . . This STILL Doesn't Allow Full Access for Final Assembly . . .

Any Ideas on HOW to Further Dissemble to Gain More Access ?

Thanks for All Previous Help & Cheers from Orion12 . . . Still NOT Out of the Woods Yet . . . But Made SOME Progress . . . I don't currently SEE what the Next Step Is . . . Help Please !
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Last edited by Orion12; 05-25-2015 at 04:10 PM. Reason: Update Info . . .
05-27-2015, 04:30 PM   #12
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Update . . . Got it Back Together with Everything Working ( Except ) the Aperture Adjusting Bracket got Twisted when the Lens Dis-Assembled itself Originally . . . I have to Figure Out a Solution for that Later . . . For Now It's Back On Line with a Fixed Aperture of ~f6.3 which is it's Sweet Spot . . .

If anyone Knows of Any Parts Sources for these Discontinued Pentax 6x7 Lens . . . Please Let Me Know !

Many Thanks for ALL of Your Help & Inputs . . . Very Helpful . . . Cheers from Orion12
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