Special Precautions - Canon A-1 Repair Manual

INTRODUCTION
The CANON A-l is the pinnacle we have been striving for in an
AE SLR-- a completely digitally controlled camera.
The mechanical parts are based on, and nearly identical to, the
AE-l. To troubleshoot and repair the A-l, experienced gained
on the AE-l is important, and consideration of digital timing
is necessary.
The electrical circuit of the A-l is quite different from the
AE-l. The main components are five intergrated Circuits,
(OPT, INPUT, CPU, OSC/ INTERFACE and DECODER DRIVER). Digital
signals criss-cross to and from these
Ie
and to their mechanical
interfaces . . To repair the camera, signal sequence and timing
must be understood. Digital basics, including code reading,
and oscilloscope operation are other necessary skills.
Special Precautions
1. Many parts are interchangeab l e between the A-l and AE-l.
However, other parts that appear quite similar to AE-l
parts are either slighly different in size, strength or
material and are not interchangeable. Special attention
should be paid to parts control to insure that the cor-
rect parts are used.
2. The A-l shutte r is controlled in 1/8 step intervals.
For this reason the 2nd curta in latch adjustment has been
changed. Rather than having a space between the latch
and latch cam, they press against each other in this design.
3. Because of the digital control, the positioning of the
information input brushes i s very important. Each one has
a special check point built into the pattern. This point
(called a check pattern or check bit) should be used to
accurately adjust the contact. If improperly adjusted,
improper exposure or viewfinder information will result.
Especially, if the AV brush (Section 2-11) is not correct-
ly adjusted, the error mark (EEEE EE) will be displayed
and the shutter will be locked.
4. The maximum aperture pin height adjustment (Section 2-8,
2-9) is differe nt from the AE-l. See section 2-8 and 2-9
for the correct procedures. This adjustment has a direct
effect on the viewfinder information and should be ac-
curately performed.
5. Lock-out voltage (LV): The low voltage interlock for
this camera is 3.1 to 3.5 volts .
1 -