Philips CDR775 Service Manual page 16

Faultfinding Guide CDR775
Figure 8-5 'Key matrix scan line'
Easy jog knob
Rotary operation
The easy jog knob (1050) incorporates a whole heap of user
control possibilities in just one knob. Without the knob being
operated, pin 1 and 3 of the knob (and thus pin 16 and 17 of the
display controller), maintain the +5V level. Turning the knob
clockwise briefly connects pin 1 to GND followed by pin 3.
Figure 8-6 Turn clockwise'
Turning the knob anti-clockwise briefly connects pin 3 to GND
followed by pin 1.
The pulses created this way arrive at pin 16 and 17 of the
display controller. The first pulse to arrive tells the controller the
direction of the rotation. Counting the pulses reveals the
amount of rotation. Combining and decoding this information,
the display controller will execute the appropriate task.
Push button operation
This button connects to the key matrix lines and thus the
operation is identical to the ordinary keys. Without being
pressed, pin 4 of the easy jog maintains the low level, pin 5 the
high level. When pressed the scanning signal goes through the
closed contact of pins 4 and 5, and can be checked at both
pins.
IR receiver • remote control
In the CDR570/930 the IR receiver TSOP1736 (6101) is
mounted on the display board. In the CDR770 that same IR
receiver (6200) is mounted on a small board together with the
headphone socket. In the CDR775 the IR receiver (6200) is
mounted on its own small board. In all versions the IR receiver
connects to the display controller. The signal coming from the
receiver can be checked at pin 22 of the display controller. This
signal is normally high (+5V). When the remote control is being
operated, pulses mixed in with the +5V can be measured. The
oscillogram gives an indication of how the signal looks like with
the RC being operated.
Figure 8-8 'IR receiver signal'
Figure 8-7 'Turn anti-clockwise'