Lyle (lo@xxxxxxxx) asked:
<<
I don't have the mirror lockup on auto--it fires ok--but I seem to have the
same shutter speed (1/60 I would estimate from the sound of it) on auto no
matter what the aperture setting. Would this similarly indicate either photo
diodes or switch as in the case of the mirror lock-up? On manual works ok,
but these are different detectors aren't they?. Are photodiodes still
available, and is this a job a handy person could do, or is it off to the
shop
>>
1) Yes the detectors are quite different on manual.
But if the shutter speeds vary correctly when the shutter speed dial is
changed in manual this does indicate almost all the electronics for Auto are
working.
2) If one or both of the photo diodes were leaky or shorted it might well
cause the shutter speeds to always be some fast value. Or if the circuit
board were badly contaminated it might also cause similar symptoms. If all
times are correct on manual then the rest of the parts ,amplifiers cct bds
etc are all working correctly.
3) If the switch were defective or both diodes open circuit it would tend to
cause lockup since the normal LED exposure limiter would not work if the
photo sensors do not work.
4) If the photo diodes are available it is still relatively difficult to work
on the boards as they require extreme cleanliness and they require use of
silver alloy solder (metalized ceramic) and extreme static precautions as the
diodes connect to unprotected Mosfet transistors. If the photodiodes are not
available it should be possible to get suitable substitutes although diodes
with the right filtering ("blue enhanced" etc) are harder to get and some
sort of crude lens may be necessary. It is probably necessary to recalibrate
auto mode with any new sensor.
Regards,
Tim Hughes
>>Hi100@xxxxxxx<<
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