Wow, thanks Clint !!
Now I will start studying your answer.... need to read it thrice before
understanding :^)
At least it seems I was able to put up the question properly
Fernando.
on 2/06/2005 14:36, PhotoSphere Olympus Camera Service at olyfix@xxxxxxxxxx,
wrote:
>
> The ASA setting provides both an electronic and a mechanical input to the
> system -- the mechanical input affects both Auto and Manual modes, the
> electronic only Auto.
>
> A cam on the ASA mechanism mechanically sets the meter movement so that it
> is properly positioned for both Auto and Manual settings. Another
> mechanical input also positions the meter according to the aperture set on
> the lens.
>
> When the mode selector switch is set for Auto, the meter circuit is
> calibrated with fixed resistors so that the needle points to the approximate
> shutter speed the camera may deliver (varying according to the light that
> strikes the two CdS cells by the eyepiece), with the meter mechanically
> positioned by the ASA and aperture inputs as noted above. In Manual mode,
> the shutter speed selected is also input into the equation via a stepped
> resistor connected to the shutter speed dial.
>
> The mode selector switch has a dual function -- the circuit on top largely
> affects only the meter, but is linked to a mechanism that sets the Main
> circuit (below the mirror) for either Auto (variable) exposure or Manual
> (fixed) speeds. It is the switch on the Main circuit that selects either
> the Auto exposure function, with it's comparator/amplifier circuit (affected
> by the ASA's VR input) to vary time according to the light reflected into
> the SbC sensor, or the fixed resistances input via the shutter speed dial.
>
>
>>
>> BTW, after trying to understand circuit diagrams of the OM-2 still can't
>> figure out how is it that ASA dial (AR circuit board) gets disconnected on
>> Manual mode. Seems this part of the circuit is 'on' only on Auto mode,
>> then:
>> how does CdS meter gets its info on which ASA setting it's working on
>> while
>> on Manual mode ?
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