Fernando Gonzalez Gentile wrote:
> Well, this made me lose about 6 RDPIII frames, and made me feel surprised.
> Short story: mirror locked up .... It's working Ok now, but ...
> what happened !? Or was it the self-timer, which I had left On ? More
> enigmatic is that it managed to trip the shutter once, while being
> failing before and after !.
>
Classic symptoms of two things.
1. Failing battery. Although most characteristic of non-silver oxide
batteries, I could see this happening with silver oxides at just the
right stage in their useful lives. Especially with the 303/357, with its
long slow decline discharger curve (as opposed to earlier 357 later
357/303).
The why is simple. Battery load in metering, lighting test button,
operating self timer, etc. is quite low. AND, none of these but the
battery check cares much about the voltage.
BUT, battery drain holding the second curtain open during exposure is
quite high. AND, the exposure circuit is very picky about voltage, as
insufficient voltage could mean mis-exposure. Voltage is checked just as
maximum strain is put on the battery, it fails the test and the camera
aborts the exposure.
Unfortunately, the battery check light on the OM-4 series bodies is not
very good. Check with a voltmeter. If voltage is below 1.5v, try another
set. It doesn't matter if the batteries are "new", as manufacturing
defects or time in the distribution channel crop up from time to time.
2. Poor electrical contacts in the battery circuit. This is most
commonly loose screws holding the bottom plate on, but can be
oil/corrosion where the plate makes contact or elsewhere in the circuit.
The why is similar to above. At low current, there is little enough
resistance through the problem spot that everything seems normal. With
higher current, the voltage loss across the poor connection is great
enough to lower the voltage too much for shutter operation.
If truly fresh batteries and tightening the bottom plate screws don't
cure the symptoms, take the plate off and clean the bottom of the body
casting around where the screw holes are, including use of a rough
eraser, fine sandpaper or some such on at least one hole.
Moose
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