Onkyo TX-DS494 Service Manual page 31

CONFIRMATION
CONFIRMATION OF PROTECTION CIRCUIT
1. Confirmation of speaker relay
Confirm that the speaker relay turns ON approximate 5 seconds after the power switch is turned ON.
Confirm that the speaker relay turns OFF immediately after the power switch is turned OFF.
2. Confirmation of DC detection circuit
1. Press and hold down CD button, then press SPEAKERS A and SPEAKERS B buttons at the same time.
2. Press DVD button, while "TEST-1_" on the FLtube is displayed.
During "TEST-1-00" on the FL tube is displayed.
3. Press SPEAKERS A button button
During "TEST-1-01" on the FL tube is displayed.
4. Apply DC 1.5 3V to MULTI CHANNEL INPUT terminals with no load.
Confirm that the speaker relay turns OFF.
5. Apply DC -1.5 3V to MULTI CHANNEL INPUT terminals with no load.
Confirm that the speaker relay turns OFF.
3. Confirmation of Current detection circuit
1. Press and hold down CD button, then press SPEAKERS A and SPEAKERS B buttons at the same time.
2. Press DVD button, while "TEST-1_" on the FLtube is displayed.
During "TEST-1-00" on the FL tube is displayed.
3. Press SPEAKERS A button button
During "TEST-1-01" on the FL tube is displayed.
4. Connect Differentiator below and apply the 50Hz square signal to the MULTI CHANNEL INPUT terminals.
5. Adjust the attenuator or Volume so that the output level becomes 35V p-p.
6. Confirm that the speaker relay does not turn OFF when a 3.0 ohm load is connected.
7. Confirm that the speaker relay turns OFF when a 1.0 ohm load is connected.
AF Oscillator
Differentiator
50Hz
Square wave
0.1 F
3.3k
Input
10k
GND
Differentiator
CD
Terminal
Attenuator
3.3k
1SS133
Output
0.01 F
GND
Speaker
terminal
Unit
Load
Oscillo-
scope
TX-DS494/HT-R490
35Vp-p