rtomcala@xxxxxxxxxxx writes :
<< Tim,
I don't think so! I think that you might want to read John H's post
of yesterday or the day before. I still stand by my statement (which
John backs up).
Rand E.
>>
Rand,
I have been considering modifying (extending) my OM2 auto limiting
action in "off mode" so have looked at both schematics pretty carefully.
I have both the OM2 and 2N Olympus service manuals with full circuit
schematics and descriptions. The OM2N service manual in particular has an
extremly detailed comparison with timing diagrams comparing operation of the
OM2 to the upgraded OM2N circuit. I actually posted detail about this
previously on an old thread. (you could check archives) But will just quote
here from the OM2N service manual :
"AUTO maximum exposure time (auto limiter)
In the old model ,maximum exposure time was subject to wide variation,just as
in the case of its off limiter, with changes in ASA sensitivity setting. As
will be noted in the following two graphs, a substantial improvement is
secured.
.... (detailed graphs comparing OM2 and OM2N LED timing,integrator output
etc).....
After about 2 minutes ( 2 to 5 minutes) of the turning on of the main switch
, the LED lights up brighter than in the old type. As a result, there is no
possibility of the maximum exposure time stretching out from 5 minutes to up
to 20 minutes. "
The description/specs for most of the timing limiting are really for the
100ASA setting although this is not well spelled out in the manual and the
limiter will have some small dependency on ASA but much reduced over the OM2.
The OM2N circuit description of the added limiter circuit also shows that you
can trim the timing of the limiter within some restrictions (since some of
the timing parameters interact) by tweaking the resistors. The limiter
circuit is in the base of the camera so is relatively easy to get at to
modify the 2N limiter action. For example you could increase the time
modestly if your camera were on the low end of the 2-5min spec.
On the other hand the OM2 has a resistor that is factory selected for
each camera to supply the LED with the right current to limit exposure times,
this means again you could trim this to increase limiter time if you did not
mind the possibility of exhausting your batteries with extreme length
exposures.
Regards,
>> Tim Hughes <<
>> Hi100@xxxxxxx <<
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