Canon A-1 Repair Manual page 144

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16. El (16P)
Main power supply voltage input.
(El
= Approx. Vbatt. -O
. 3V)
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17. LED (17P)
Self timer and battery checker LED operation signal.
18 . MGl (18P)
5V
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Fig . 3-46
Fig. 3-47
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OOf
ts
Mgl is the AE magnet .
o peration signal gate .
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The condition of Mgl can
be determined quite ac-
curately by studing the
waveform on the Mg 1
release . Scratched or
fould armatures
can be recognized.
Uneven release of
MGl the AE mechanism and
shutter can be
GND
seen.
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When the currnet is terminated,
a ver y hi gh voltage spike occures .
To control this a zener diode 1s
'incorporated into the IC which
limits the spike to the Pl
level shown in Fig. 3-47.
When the yoke and armature
actually separate another
spike occures. The timing and
size of the spike are affected
by condition of .the magnet.
Contamination, especially oil,
can cause the yoke not to
release properly and T becomes
long. Misalignment of the armature
and yoke produce a smaller than
normal reverse current spike.