FA80-320


MattMatic

Link Posted 23/10/2012 - 11:08
This is a very long shot...

I have an optically great FA80-320 that appears to have had some impact damage. There are three of the mount screws that are almost stripped in the plastic, and the electronic contacts 'fall' into the lens when mounted so that the body can't see the lens properly.

I've had it lying around, feeling that it's not worth coughing up the cash to get repaired.

Yesterday I had a Google for dismantling guides and found a few on RiceHigh's site. That helped a lot to give some confidence So early this morning I took the plunge and dismantled the lens...

Actually not half as complicated as I'd feared.

Turns out the plastic mounts have cracked, and the flexible PCB for the electronic pins has had its mounts broken too. I'm considering gluing it back to a serviceable state... thinking of Sugru or Araldite for the PCB, and controlled heat / superglue / Araldite for the plastic lens mount posts.

Don't suppose anyone has a dead black FA80-320 lying around that I could butcher? (Or any other suggestions for fixing)


BTW, have taken a load of images with the Q so you can all see what fun I've been having

Thanks
Matt
http://www.mattmatic.co.uk
(For gallery, tips and links)
Last Edited by MattMatic on 23/10/2012 - 11:09

Algernon

Link Posted 23/10/2012 - 11:28
Worth fixing. The normal problem seems to be wobbly
barrels, which is what stops me buying another.

I used to love the bokeh off that lens.

-
Half Man... Half Pentax ... Half Cucumber

Pentax K-1 + K-5 and some other stuff

Algi

MattMatic

Link Posted 23/10/2012 - 11:42
Algi,
Yes, the bokeh and general rendering with the 8 aperture blades is so much nicer than the DA55-300.

Think it's going to be superglue and Araldite later...

Matt

BTW, Sugru is rather astonishing stuff. Worth watching this video Right up Don's street for mashing things together

EDIT: Some Sugru photography ideas
http://www.mattmatic.co.uk
(For gallery, tips and links)
Last Edited by MattMatic on 23/10/2012 - 12:09

McBrian

Link Posted 23/10/2012 - 12:57
Nail varvish remover might be a cheap option to repair the plastic mounts although it will depend on the grade and quality of the plastic used in the lens.

I also wonder if the cheapo FA28-80 uses the same board for the pin?

MattMatic

Link Posted 23/10/2012 - 13:28
Thanks Brian! I presume NVR will dissolve the plastic somewhat?

The PCB is fine, it's just how it's held in place. Stupid design really! Think Sugru may be the stuff as it has some 'give' and can be removed if really needed. The only way into the PCB is down the barrel of the lens - yuck!

Matt
http://www.mattmatic.co.uk
(For gallery, tips and links)

Don

Link Posted 23/10/2012 - 15:26
MattMatic wrote:
Algi,
Yes, the bokeh and general rendering with the 8 aperture blades is so much nicer than the DA55-300.

Think it's going to be superglue and Araldite later...

Matt

BTW, Sugru is rather astonishing stuff. Worth watching this video Right up Don's street for mashing things together

EDIT: Some Sugru photography ideas

true sugru is awesome stuff!

sometimes is the silliest things you need for a project that get the job done..
also hot glue is great for "injection molding" parts you might need... use something like sugru or plumber epoxy to make the mold than inject hot glue for a soft pliable plastic part...
ps there are solvent weld glues that are for plumbing and auto repair applications that might work but you'd have to do some research before using..
cheap prop making:
link
also for a halloween display:
link

Fired many shots. Didn't kill anything.
Last Edited by Don on 23/10/2012 - 15:37

pentaxian450

Link Posted 23/10/2012 - 18:42
To repair screw holes, you can use epoxy/metal filler made by companies like Loctite or Devcon. It comes in a stick that you cut to size, and just mix by squeezing it like dough.
Yves (another one of those crazy Canucks)
Last Edited by pentaxian450 on 23/10/2012 - 18:43

jeallen01

Link Posted 23/10/2012 - 20:42
MattMatic wrote:
This is a very long shot...

Don't suppose anyone has a dead black FA80-320 lying around that I could butcher? (Or any other suggestions for fixing)
Matt

Actually, I do have one because of my hamfistedness after you tried to give me some help fixing my own silver 80-320mm with a loose barrel - but I lost some of the small screws

Couldn't bear to throw it away, so the all the main bits are in a drawer - PM me if that would be any use!!
K-3 II, K-3 and a K-70 from SRS (having now relegated the K-30 /"K-50" to a backup body), & some Sigma and Pentax lenses (and a lot of old 35mm gear!)
Last Edited by jeallen01 on 23/10/2012 - 20:43

MattMatic

Link Posted 23/10/2012 - 21:00
Thanks Yves

Oh dear John Sorry that didn't work out. I have a couple of dud FA28-70 lenses that may have equivalent screws You'll find the images of this episode scary!

Have Sugru'd the PCB in late this afternoon. Will find out how it works by tomorrow when I can try and fix the plastic posts.

Matt
http://www.mattmatic.co.uk
(For gallery, tips and links)

MattMatic

Link Posted 24/10/2012 - 15:47


Hurrah!!

The Sugru worked an absolute treat.
My request about the screw posts wasn't 100% technically correct. It wasn't that the threads were stripped, but that the square posts has been split (thereby opening up the threads).

I'd thought I could fix with Araldite, but on further inspection it would have clashed with other parts So, I used a combination of Humbrol plastic cement (carefully applied with the end of an older screwdriver), and superglue gel.

I reckon if that doesn't hold then I'll have to convert the pillars to nut + bolt fixings. Heating up a nut to around 265C will allow me to sink it into the plastic. But this will be a one way ticket and needs the right countersunk screws.


Initial shots look fine. Will compare with DA55-300 for sharpness later.

And when I get a chance I'll write it all up with photos

Matt
http://www.mattmatic.co.uk
(For gallery, tips and links)
Last Edited by MattMatic on 24/10/2012 - 15:47

Algernon

Link Posted 24/10/2012 - 15:55
Good to hear that an 80-320mm has been rescued
Half Man... Half Pentax ... Half Cucumber

Pentax K-1 + K-5 and some other stuff

Algi

MattMatic

Link Posted 24/10/2012 - 17:02


Gallery with commented instructions and hints:

Pentax FA80-320 Disassembly Photos

Usual disclaimers apply!! Don't blame me for anything that goes wrong if you are mad enough to try this

(Photos taken with Pentax Q + Q01 Standard Prime)

LOL!

Quote:
Good to hear that an 80-320mm has been rescued

Definitely a labour of love fixing this
(But a very good learning curve too!)

Matt
http://www.mattmatic.co.uk
(For gallery, tips and links)
Last Edited by MattMatic on 26/10/2012 - 13:11

MattMatic

Link Posted 26/10/2012 - 13:03
Just a little postscript...


I forgot to say that you should check the curved PCB is level with the plastic before it sets! The little sprung 'finger' that makes contact in the "A" setting should move smoothly into place. The first time I tried it, the spring got stuck and started to deform

So, make sure it's all line up nice and snug so the spring can move into place easily (see this image where you can see the finger at the bottom of the image)

EDIT: And a kindly reader put another link on RiceHigh's blog: http://www.pentaxian.nl/index.php?topic=24882.0

Matt
http://www.mattmatic.co.uk
(For gallery, tips and links)
Last Edited by MattMatic on 26/10/2012 - 13:19

frederik9111

Link Posted 26/10/2012 - 13:15
MattMatic wrote:
Just a little postscript...
EDIT: And a kindly reader put another link on RiceHigh's blog: http://www.pentaxian.nl/index.php?topic=24882.0

glasbak wrote:

Deze lens meegekregen van Frederik9111, met doos en al, en zag er vrijwel ongebruikt uit.

Glasbak got this lens from a very kind other Pentaxian

It's a small world after all...
Imagine...
Last Edited by frederik9111 on 26/10/2012 - 13:16

Don

Link Posted 26/10/2012 - 14:42
send it over to instructables or hackaday?
Fired many shots. Didn't kill anything.
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