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Re: [OM] OM-G Focusing Screen - Removal

Subject: Re: [OM] OM-G Focusing Screen - Removal
From: "John Hermanson" <omtech@xxxxxxxxx>
Date: Tue, 24 Aug 1999 11:15:14 -0400
The  dull side of the screen must go up and the back edge of the screen must
go under the 2 spring loaded clips.

John
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----- Original Message -----
From: Chuck Norcutt <norcutt@xxxxxxx>
To: Olympus mail list <olympus@xxxxxxxxxxxxxxx>
Sent: Monday, August 23, 1999 10:05 PM
Subject: [OM] OM-G Focusing Screen - Removal


> Caution:  Long post...
>
> A while back Justin Morrison wrote the list inguiring as to the
> availability of a focusing screen for his OM-G.  The previous owner had
> managed to scratch it badly trying to remove it for cleaning.
>
> Months ago I had bought a broken OM-G (*supposedly* a sticky shutter)
> for purposes of teaching myself a bit of home OM camera repair.
> Justin's plight inspired me to dig out the old OM-G and see if I could
> figure out how to remove the screen (amongst other things).  Figured if
> I screwed it up it wouldn't matter and if I didn't then I could advise
> Justin and others how to do it.  So, here is a slightly abbreviated
> version of the note I sent Justin:
>
> . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
> How to get the screen out:
>
> The black, semi-circular, plastic piece just inside the bayonet mount
> must be removed to reveal the front, screen retaining clip underneath.
> (It is glued on with a contact-like cement)  The retaining clip is "L"
> shaped and the mounting screw is immediately behind the plastic piece.
> I was concerned that the plastic piece was also "L" shaped like the
> retaining clip but that is not the case.  What you see looking at that
> plastic piece is all there is.
>
> When the camera is assembled at the factory the sequence must be:
>  - insert screen
>  - attach retaining clip with screw
>  - glue on plastic piece inside bayonet mount
>  - glue the foam bumper over the top of the retaining clip and the
>    very edge of the plastic piece
>
> When you try to pry off the plastic piece you will see the foam bumper
> starts to move with it because the foam is glued on at the very edge.
> That's why I thought the plastic piece was "L" shaped also.  I was
> concerned that it wrapped around under the foam and that if I applied
> too much pressure it would break.
>
> The plastic piece has locating pins that serve to position it.  When you
> pry it off use a tiny flat blade as a lever and work it around the
> outside edge such that you are lifting up.  The plastic is not very
> thick or strong so work slowly and gradually all along the edge to avoid
> breaking it.
>
> You will need a #0 phillips screw driver to remove the retaining clip
> screw.  It was in very tight so be careful not to strip the head.  The
> screw is only about 2mm long so also be very careful not to lose it (I
> was being careful but still almost lost it). I already had some
> jeweler's screw drivers but I went to Radio Shack yesterday and bought a
> larger set for $10.99.  Glad I did since some of the tiniest flat bladed
> screw drivers (1/32 and 3/64) were useful as prying and lifting tools.
>
> I did not remove the foam bumper but may have to eventually.  Since the
> foam is glued to the retaining clip you still can't move the clip once
> the screw is removed. I used a sharp Exacto knife and worked it down
> between the clip and the foam until the clip was free of the glue.  I
> then used two tiny flat bladed screwdrivers on opposite sides of the
> clip to lever it out from under the foam.  I didn't pull it all the way
> out... just enough to clear the screen.  The screen did not want to fall
> out by itself so I had to encourage it by catching it's corner edge with
> the 1/32 screwdriver.  A needle would probably also work well there...
> but be careful with any metal edge or point near that plastic... it's
> really easy to slip.
>
> Anyhow, there's the saga.  Putting it all back will be a bit more
> difficult; especially if that foam strip has to be replaced.  That may
> require buying some material from the likes of Micro Tools who sell
> camera repair tools and supplies (www.micro-tools.com).  On the other
> hand maybe it will be reusable if carefully removed.
> . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
>
> Having accomplished that, I was encouraged to see what else I could tear
> apart so I set about removing the top and bottom covers.  Whatever ailed
> this camera may have included a session with the cat in the closet most
> recently mentioned by John H.  There were blue and white powdery spots
> on the top and bottom covers reminding me of battery acid.  A few of the
> screws were also rusty.  Getting them out was difficult but I managed
> without stripping the screw heads or destroying anything.
>
> A big surprise was finding the aforementioned blue and white powder all
> around the inside of the cover seams both top and bottom.  I was certain
> that I would find the inner works a total disaster.  Much to my surprise
> all the inner mechanics, electronics and optics (while not necessarily
> working) were clean as a whistle.
>
> Apart from the rusty screws, getting the bottom cover off is simple.
> Just remove the screws and wiggle the cover off.  Getting the top cover
> off is a bit more difficult but not hard.  If you have Thomas Tomosy's
> books on camera repair the OM-G cover removal is almost the same as the
> OM-10 which he covers in book 2.
>
> I first loosened all the cover screws slightly just to be sure I could
> get them out.  Four of the six were corroded and required lots of
> patience, pressure and a few light hammer taps.
>
> Next comes the rewind knob.  *First*, open the back and *don't* close it
> because you're about to remove part of the release catch.  Insert a
> blade in the bottom of the slotted rewind shaft to hold it still then
> remove the screw under the rewind handle.  Slide the shaft down till
> it's flush with the top but don't pull it out.
>
> Next to the film advance lever.  Pull the lever out halfway and remove
> the screw on the underside.  Lift off the black plastic covering the
> metal lever.  This will reveal a screw holding the advance lever to the
> shaft.  Remove the screw and the lever.
>
> Next to the ASA dial.  In the OM-10 the dial is attached to the cover
> and keyed to the mechanism underneath so nothing has to be done here, it
> just comes off with the cover.  In the OM-G the dial portion above the
> cover is screwed to the mechanism underneath.  Turn the dial to ASA 100
> and remember where you've set it.  Note that the inner part of the dial
> with the compensation markings is actually a snap-in cap to the knob
> underneath.  Look carefully and you will see the seam all around about
> 1mm from the edge.  Using a very tiny blade (the 1/64" screwdriver came
> in handy here) inserted into the seam, lift the compensation dial off
> the ASA knob.  With the dial at ASA 100 I inserted the blade at the
> index mark and the cap popped off easily.  Note that the cap has two
> tiny plastic ears.  Note that the knob has indentations for these ears
> and will not want to stay on unless put on exactly as it came off.
> Under the cap is a screw.  Remove the screw, the spring underneath it
> and then lift off the ASA knob.
>
> Remove the screws and the cover can now be slid upwards and off.  Don't
> pull it too far since there are a couple of wires running to the hot
> shoe.  Also, be careful not to lose the door latch spring.  The spring
> is located at the 10 o'clock position relative to the rewind shaft and
> is held in place by the cover.  Removing the cover will allow it to fall
> out.
>
> There you have it; partial OM-G disassembly.  Next is to figure out why,
> at *any* shutter speed setting, the thing is clicking off from 2-4 ms.
> On B, if light can get to the sensor, it acts as B should with the
> shutter opening and closing with pressing and releasing the shutter
> button.  Now the strange part.  While still on B, if the sensor is
> completely blocked (lens cap on), releasing the shutter button does not
> close the shutter... it goes on to make an apparently timed exposure of
> several seconds.  Now it gets wierder.  If I change the ASA dial the
> apparently timed exposure gets longer or shorter according to the ASA
> setting.
>
> So, something of the electronic timing is still working but it's
> apparently confused as to what mode it's in.  I cleaned and adjusted the
> wiper contacts under the mode switch but that had no effect at all.  The
> ASA dial apparently does something so next is on to the contacts for the
> shutter speed dial.
>
> Wish me luck, I haven't destroyed it so far. :)
>
> Chuck Norcutt
> Woburn, Massachusetts
>
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