Onkyo TX-DS898 Service Manual page 4

ADJUSTMENT AND CONFIRMATION PROCEDURES
3. Confirmation of Current detection circuit
Set the unit to "TEST-1-00".
Connect the differentiating circuit and apply the 200Hz square signal to MULTI CHANNEL INPUT terminal.
of each channel.
Adjust the attenuator or Volume so that the output level becomes 35V p-p.
Confirm that the speaker relay does not turn OFF when a 3.0 ohm load is connected.
Confirm that the speaker relay turns OFF when a 1.5 ohm load is connected.
CR
OSCILLATOR
DIFFEREN-
TIATING
CIRCUIT
200Hz
SQUARE
INPUT
0.1 F
3.3k
GND
Confirmation of fan
Set the unit to "TEST-1-00".
Apply the 1kHz -30dBV signal to the left channel of MULTI-CH terminal with no load.
Confirm that the fan rotates slow speed after few seconds.
Connect the 1.2 kohm/1W resistor between terminals COM and TH-1 of P6401 with no input signal.
Confirm that the fan rotates slow speed after few seconds.
Next apply the 1kHz -30dBV signal to the left channel of MULTI-CH terminal with no load.
Confirm that the fan rotates high speed after few seconds.
Connect the 1.2 kohm/1W resistors between terminals COM-TH-1 and COM-TH-2 of P6401 respectively with no input signal.
Confirm that the fan rotates high speed after few seconds.
MULTI
CHANNEL
INPUT
ATTENU-
ATOR
3.3k
1SS133
10k
Differentiating Circuit
P9503A
COM
TH2
TH1
SPEAKER
TERMINAL
UNIT
OSCILLO-
SCOPE
OUT-
PUT
0.01 F
NAETC-7238
TX-DS898
35Vp-p