Input Ic Adjustment (A/D Null Adjustment) - Canon A-1 Repair Manual

4.3 INPUT IC Adjustment
(AID
NULL Adjustment)
1 . Short CAD(-) and CAD(+). (Fig. 4-5)
Va
~.(
PI
D
J"
INPUT Ie
C-(4PI CAD
CAD-(3P~~~~~~~
ADIluu.II2P
AONuLL:z( I
PI
2. Measure the voltage from CAD to ground (Vl).
3. Measure the voltage from VC' pad to ground (V2).
4. Vl and V2 should be within 0.1 mV of each other.
If they are not, the NULL adjustment must be made.
Adjustment:
Method:
Note:
ADNUL ADJ. ' Resistor (Normally approx. 20KQ)
Identical to the OPT IC OFFSET adjustment.
If the following are correct, the
AID
NULL is normally correct.
i) If the SPC output is correctly adjusted by VRG
and VRL (Section 2-21), or,
ii) If the camera stops down to the correct flash-
commanded aperture when using the 199A.
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