2-4
EA-80
2-4-2. Switch, Indicators, Audio and
Communication Circuit Check by an
Oscilloscope
1. Connect the pin 7 of CN1 on the AU-254 board to the +
terminal of the power supply, and the pins 1 and 2 of
CN1 to GND of the power supply.
Use the modified RK-8XXX cable to facilitate the
check required. (Refer to step1 in 2-4-1. Switch,
Indicators and Audio Circuit Check.)
2. Connect the pin 4 of CN1 on the AU-254 board to
GND of the power supply.
3. Set a DC out voltage to
+
15 V, and turn on the power
switch.
4. Two seconds later, all response indicators (D1 through
D6 on the SW-952 board) flash.
5. Disconnect the pin 4 of CN1 on the AU-254 board
from GND of the power supply.
6. With transmitting “55H” code from the pin 3 of IC1
(TxD terminal) on the SW-952 board, all response
indicators light.
With all response indicators flashing, that is, without
lighting, it is abnormal. Check the signals between the
pin 1 of IC1, the pin 3 of IC1 and the pin 4 of CN1 on
the AU-254 board.
7. (a)
Switches and indicators check
Perform the same step as step 7(a) in 2-4-1. Switch,
Indicators and Audio Circuit Check.
(b)
Audio circuit check
Perform the same step as step 7(b) in 2-4-1. Switch,
Indicators and Audio Circuit Check.
(c)
Communication circuit check
Using an oscilloscope, confirm that “55H” code is
transmitted to the pin 4 of CN1. With transmitting
“55H” code to the pin 4 of CN1, it shows the following
waveform on the oscilloscope.
b6
b
Ø
1
1
0
1
0
1
5
5
0.42 msec
H
0
TXD TERMINAL
"55 H"
Star
t bit
Stop bit
2-4-3. Indicators, Audio and Communication
Circuits Check by EA-80 connected to
LLC-8000
1. Press the POWER switch on the LLC-8000 to turn the
total LLC-8000 system on.
(Do not press the ATTEND button on the LLC-8000.
Not pressing the ATTEND button does not light the
indicator located at the left-above the monitor button on
the LLC-8000.)
2. Check switches, indicators and audio circuit by the
same steps as steps 3 through 7 in 2-4-1. Switch,
Indicators and Audio Circuit Check.
3. Communication circuit check.
When the communication is established, the indicator
that shows the student unit, EA-80, being checked and
located at the left-above the monitor button on the
LLC-8000, lights.
4. Press the POWER switch on the LLC-8000 to turn the
system off.
