SERVICE MANUAL - O. Rensch OHG

2DC
2-3-7 Operation board
The operation board consists of key switches, LEDs and 7-segment LED. The lighting of LEDs is determined by scan
signals (SCAN0N to SCAN5N) and LED lighting selection signals (LED0N to LED7N) from the main board. The key
switches operated are identified by the scan signals (SCAN0N to SCAN5N) and the return signals (KEY0N to KEY2N).
As an example, to light “L1”, the LED lighting selection signal (LED0N) should be driven low in synchronization with a low
level on the scan signal (SCAN0N). LEDs can be lit dynamically by repeating such operations.
As another example, if “K2” is pressed, the corresponding key switch is turned on feeding the low level of the scan signal
(SCAN1N) back to the main board via the return signal (KEY0N). The main board locates the position where the line
outputting the scan signal and the line inputting the return signal cross, and thereby determines which key switch was
operated.
Operation board
Main board
Key switches
KEY2N
KEY1N
YC1-17
YC1-16
K11 K12 K13 K14 K15
K6 K7 K8 K9 K10
KEY0N K1 K2 K3 K4 K5
YC1-15
D1 D2 D3 D4 D5
SCAN5N
SCAN3N
SCAN4N
SCAN2N
SCAN1N
SCAN0N
LED7N
LED6N
LED5N
LED4N
LED3N
LED2N
LED1N
LED0N
YC1-14
YC1-13
YC1-12
YC1-11
YC1-10
YC1-9
YC1-8
YC1-7
YC1-6
YC1-5
YC1-4
YC1-3
YC1-2
YC1-1
L8 L17 L26
L7 L16 L25
L6 L15 L24
L5 L14 L23
L4 L13 L22
L3 L12 L21
L2 L11 L19 L20
L1 L10 L18
7-segment
LED
LEDs
Figure 2-3-12 Operator board circuit block diagram
2-3-13