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[OM] Re: OM-10 and false shutter speeds

Subject: [OM] Re: OM-10 and false shutter speeds
From: Moose <olymoose@xxxxxxxxxxxxxxx>
Date: Sat, 12 Mar 2005 13:19:18 -0800
orava@xxxxxxxx wrote:

>I tested how the other manual adapter works with my OM-10 and found out that 
>the
>problem remains... Every now and then the shutter closes after a significantly
>longer time than it should... I've got to look for those writings about oily
>magnetic...
>
That is almost certainly the problem. It is a very common OM-10 problem, 
particularly on those with serial numbers below 2,000,000. Below that 
number, the electromagnet that holds back the second curtain is in the 
back of the area below the floor of the mirror box, nead the curtains 
and their mechanism. Over time, oil from elsewhere in the shutter 
mechanism migrates to the magnet. In order to make the magnets use as 
little power as posssible, they have relatively large, smooth contact 
surfaces. When oil gets in there, it creates a sort of suction, making 
it hard for the spring to pull the pieces apart. That leads to the 
behavior you describe.

With the major interior redesign at serial 2 million, this magnet was 
relocated to the front, both moving it away from the oiled parts and 
making it relatively easily accessible from the front through the lens 
mount opening by pulling up the bottom of the mirror box . The redesign 
also involved replacing plastic shutter curtain rollers with metal. 
Clint has speculated that the major disaster of sticky magnet syndrome 
with early OM-10s was partly a result of over oiling in manufacture to 
keep the plastic parts from wearing prematurely.

In any case, if you have the early version, home repair is only for the 
fairly mechanically adept, as the magnet is way back by the curtains and 
pretty well covered by a flex circuit attached next to it. With small 
tools and adept fingers, it is possible to get a piece of kimwipe or 
other lintless cleaner with solvent in there, but it is a fussy job. I 
think it might perhaps be easier coming in from the back with the 
curtains held open?

On the later models (and the OM-20, 30,40,F,G,PC), sticky magnet 
troubles are rarer, but still happen. Happily, magnet cleaning on these 
models is not hard for the reasonably mechanically adept. The bottom of 
the mirror box is just glued down with rubber cement, and may be easily 
pried up with a thumbnail, revealing the magnet, which may be cleaned 
with a little bit of lintless wipe and solvent. Apparently, the OM-2(n) 
also, but rarely, may get sticky magnet, but I've never dealt with that.

OM-10s are so cheap that having someone repair it is uneconomic. An 
OM-20 (G), is a much better cheap second body. It included all the 
improvements of the late OM-10 bodies with manual function built in. An 
even better second body, if you want the auto functions, is an OM-2n, or 
for manual only, an OM-1(n). The single digit bodies were manufactured 
to a much higher standard than the double digit bodies and the 1 and 2 
will be fully repairable for many years into the future.

Never throw an OM-10 away. The prism may be used to replace an OM-1 
prism damaged by rotting foam, thus prolonging the useful life of a 
great camera.

Moose



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