Canon EOS 20D Digital, Service Manual

Page: 99 / 374

• CMOS sensor with a high pixel count developed and manufactured by
Canon.
•
Higher integration of circuit boards.
• Streamlined assembly and adjustment process.
3) Shutter release mechanism
The shutter release mechanism is
the same as the EOS 10D's. The
time lag from SW-1 ON to shutter
release is approx. 65 ms (within 3.5
stops of maximum aperture). The
viewfinder blackout time is approx.
115 ms. Both figures are much shorter than the EOS 10D.
4) Electrical components
The EOS 20D's basic circuit board configuration consists of five hard circuit
boards centering on the digital control circuit board and camera control circuit
board. These boards are connected to 22 flexible circuit boards.
The EOS DIGITAL REBEL/EOS 300D DIGITAL has the digital control circuit
board and camera control circuit board on one large hard board. However, the
EOS 20D has split these two boards to afford more a compact size and flexibility
in the exterior design. It also makes assembly adjustments more efficient.
Although separating the two boards normally increases the cost, the cost was
reduced by using a suitable layout of parts and a streamlined board shape.
Fig. 034 on page 30 shows the location of major mechanical components, and
Fig. 035 shows the location of major circuit boards. Fig. 036 shows the cross
section at the center.
The main features of the major circuit boards are as follows:
(1) Digital control circuit board
This board uses a high-density, 10-layer board (3-4-3). It consists of the
following circuits: ADIC that converts the output from the CMOS sensor into
digital signals, an image signal-processing circuit that has an IC called TG
which generates the CMOS sensor's drive pulse, a digital image-processing
circuit that includes DIGIC II, a memory circuit that includes an SDRAM for
storing images, and a TFT control circuit that includes the TFT liquid-crystal
control IC.
Also, the board's second and ninth layers are basically GND layers. They
prevent signal interference between the top- and bottom-side patterns and
inner pattern. Misoperation due to noise is thereby prevented.
Technical Information
27
Table 013 Shutter-release stroke and pressure
330g SW-1 ON to SW-2 ON
Standby position to SW-1 ON 0.55mm
140g
- 1.3mm Shutter button protrusion
Pressure Stroke State
0.3mm