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10-17-2012, 01:54 AM   #1
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Spotmatic F focusing screen dust/dirt

I picked up a really good condition Spotmatic F on eBay.
The only downside I found open inspecting it closer, was that there was bits of dust/grime/dirt on the focusing screen (when looking through the viewfinder, it's very obvious). Probably too annoying to do nothing about it.

I have a little vanguard lens cleaner with air-blower which I tried to blow off any excess dirt on the viewfinder glass, focus mirror and the focusing screen but no luck.

Is there anything else I could do?

Thanks in advance!

10-17-2012, 03:02 AM   #2
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Although commonly the foam from the mirror seal can get on the focusing screen facing the mirror, some bits can get inside between the prism and the screen... as well as the seal around the prism can decay and do the same.

If this is your case, then the need to disassemble the prism and cleaning under it will be needed.
10-17-2012, 03:11 AM   #3
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I think that may be my case, because most specs of the dirt can't be seen on the focusing screen or mirror. So my guess is that it is indeed the prism. Yikes.

Is that a job for a professional or can it be done at home?
10-17-2012, 05:52 AM   #4
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I have the same thing on a few older slr's as well.

It always bothered me when i first noticed but after a while not so much.

I stopped it from getting worse by changing out the mirror foam.

10-17-2012, 08:02 AM   #5
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QuoteOriginally posted by insphere Quote
Is that a job for a professional or can it be done at home?
It depends on your skills and confidence in opening the body and removing the prism. The basic tools are the cross tip drivers... JIS is best and a device to undo the small spanner ring that holds the counter dial assembly down. If you go the professional direction, it is not a complex job for them.

If you would like to DIY it, I'll prepare some info about it... if you need it.

Last edited by MysteryOnion; 10-17-2012 at 09:58 AM.
10-17-2012, 05:23 PM   #6
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Well, getting it to a professional would probably cost like $150.

I think I might look into trying it at home then,

I'd say I'm pretty good at putting things back together, well when I concentrate anyway :P

What is the worst case scenario, risks that I'd be taking?

If you could prepare some information, that'd be awesome. Thanks.
10-18-2012, 07:12 AM   #7
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QuoteOriginally posted by insphere Quote
What is the worst case scenario, risks that I'd be taking?
Only hazards might be wire damage, meter damage and scratching the glass surfaces in the camera... if not careful.



QuoteOriginally posted by insphere Quote
you could prepare some information, that'd be awesome. Thanks.
I'll try to throw some info together, however, give a repair manual a look.
http://www.robertstech.com/manuals.htm

or

Pentax Manuals

The quick list is...

Remove Rewind Knob - by wedging the spool prongs and turning know reverse from arrow... thread lock might make it tough.
Remove Retention Ring - small spanner ring, may need a pointy needle nose or scissors.
Remove Counter Bezel - three tiny screws... need not remove completely, just loosen.
Remove Counter Dial - Screw is left-hand or right... I forget, so don't force.
Remove Bayonet Lock Ring - remove screws and rotate ring to clear off
Remove Speed Dial - center pin spanner screws
Remove Shell Screws - cross head screws and the shell should slide up to remove

Prism is held by a metal band and two springs hooked to it and the top of the mirror cage rim. Note the positions of the anchor holes as they are tricky to find later.

When the space between the prism and screen is exposed, you are also in the area of where the meter needle is located, so be very careful when cleaning...

... otherwise, I'll have more details info about the Spotty-F later.
10-19-2012, 04:28 PM - 1 Like   #8
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Step 1.


Lets look at removing the rewinding knob.
Taking a tool to wedge into the prongs to hold it stationary we can spin the knob counter-clockwise to remove

Step 2.


We need to spin this off with a pointed end spanner tool or something


I my case I have a modified jewelry priers ground down to points. It is great for loosening all pin or point or small slotted rings, but slow for spinning them off.


Watch out for the ball bearing. I tape them down to the desk to keep them where I can find them later.

Step 3.


Shutter speed dial is again, pin spanner and it spins off with a counter clockwise direction
Note the positions of the dial and the tabs under it to reattach later.


Step 4.


Bezel of the counter is held down by three tiny flat slotted screws. No need to remove just loosen until the slightly protrude out.

Step 5.

The number dial is secured with a slot screw and it is removed by turning clockwise.


Gently pry out from the sides.

Step 6.


Another spanner job. This is a clockwise to remove retainer. Once the retainer is off you can lift the dish out.


Step 7.


Next is the bayonet retaining ring. Three cross head screws lock it in place. Once the screws are removed the ring can by coaxed around to remove the lever. Also, lift the dust shield out of the way.


Step 8.

Now you have three screws to remove that holds the shell down. Note that they are different types and lengths. One forward the rewind side is long-ish and one closer to the viewfinder is narrow and short. The one next to the advance lever area has a wide head.


Step 9.


You have now accessed the insides.


Note that the two of these spring must be unhitched from the strap. Note also where they are attached to below as to fit them later.
Also note that the prism has a soft plastic cover and it will be removed and set aside, but do take care not to nick the black surface of the prism while continuing.


To remove the prism next you first have to loosen one of the clamp screw. Try not to move the other as they together set the alignment.


That is it I hope.

I suggest you blow carefully off the crumbs first. Do not invert the body or risk spilling out the parts of the screen.


Last edited by MysteryOnion; 10-21-2012 at 07:05 AM.
10-20-2012, 10:45 PM   #9
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Wow, what a brilliant guide.

Thank you very, very much!

I will put aside some time soon to give it a go.

I'll update this when I'm done

On another note, got myself some 200 speed film today to play around with the camera.
01-30-2017, 08:21 AM   #10
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pentaprism sealing foam

I read with interest all the thread, there is one thing I need to understand:
how did you substituted the foam used to seal the pentaprism? It seems to be a sealing foam and I was thinking to use some seal silicone or similar... but I'm open to suggestions

The old foam is all gone and in my case was what caused the dirt between the pentaprism and the focusing screen (or better the lens covering it).

Thank you

L.
01-30-2017, 11:03 AM   #11
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QuoteOriginally posted by Barb Quote
I read with interest all the thread, there is one thing I need to understand:
how did you substituted the foam...
Welcome to the Pentax Forums!

You have awakened a "zombie" thread. @MysteryOnion has not been posting much of late and may not reply to your question, even though it is a very good one. A craft or hobby shop may be a good source for replacement foam, particularly if they cater to model railroad or RC model enthusiasts.


Steve
02-06-2017, 02:28 PM   #12
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Thank you!

I know I have wrote in a very old thread.

BTW, for future readers that found the thread on google as I did, I solved the problem with some black seal silicon. It works perfectly.
It is pretty easy to remove the old foam (being careful not let the debris go inside the camera) and reach the top lens over the focusing screen.
The silicon seal works perfectly and there is no difference with the foam seals.
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