On Mon, 26 Jun 2000 19:28:31 +0200 (CEST), Thomas wrote:
>The OM2n is in for repair currently. The problem is a
>"wierd" behavior of the shutter: first time I shoot a picture the shutter
>is "hanging", yielding a much longer shutter speed than what it is
>set for. Then for the following shots, the shutter functions
>correctly. Not sure what it is, but the good guys at Olympus Denmark will
>probably figure it out and clean up the camera such that I will have a
>"looks-feels-works-like-new" OM2n soon.
That may be the ASA resistor that needs cleaning. Happens on the
OM2SP too, but in its case the shutter speed goes way too fast. It's
happened on two of my 2n's and the 2SP.
If the shutter speed is consistent in manual mode, it is *not* an oily
magnet; far more likely to be the above.
>So should I summarize, my OM2s/p and OM4 have never given problems,
>whereas the OM1n and OM2n both have. In truth, the OM1n/2n are older and
>have alltogether run more films.
To be frank, our 2SP (among 3 OM1's and 4 OM2n's) has been the "dog".
>Also, I believe that if something electically goes wrong in an OM2s/p,
>then one is pretty much lost. I am of the understanding that only a very
>few places actually have electrical circuits in stock for OM2s/p, and that
>they further are not being produced any more. (Hence - since the OM2s/p
>imho. is the worlds 8th wonder - I am always on the looks for good
>OM2s/p's...)
The OM2n has a delightfully simple, all analog timing circuit. You
could build it yourself if you could get small enough individual
parts. It works (in auto mode) by comparing the voltage across a
timing capacitor that is charged via the photodiodes, with a voltage
that's derived from the film speed setting (the ASA resistor). The
capacitor voltage rises quickly in bright light shone from the film
plane, slowly in dim light. When the capacitor voltage exceeds the
reference, the shutter closes. That's it! Beautiful, elegant, simple!
When the ASA resistor gets dirty, the wrong film speed reference
voltage is sent to the comparator and it thinks the film speed is very
low. It often happens in the first shot after a "rest"; the vibration
(!) from the first shot usually restores the ASA resistor contact. Try
wiggling the film speed / exposure compensation dial a few times
before shooting. If that seems to restore normal operation, that's the
problem.
Regards
--
John Gruffydd (Mold, Wales, UK)
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