Sony STR-DB925 Service Manual page 4

DSP SELF DIAGNOSIS FUNCTION
This unit is equipped with a DSP self-diagnosis function.
After completing self-diagnosis, the "DSP TEST MODE" can be set, where signals input from the external equipment will be
assigned to the designated channels as shown in the table below.
Table-1 Assignment of Signals in DSP TEST MODE
Input Signal
FRONT L-ch FRONT L-ch + CENTER + REAR L-ch
FRONT R-ch
FRONT R-ch + WOOFER + REAR R-ch
Procedure:
1. Connect external equipment such as CD and DVD players using the DIGITAL cable (optical or coaxial).
2. Rotate the FUNCTION knob, and switch to the FUNCTION connecting the external equipment.
3. Press the INPUT MODE button, and select the type of DIGITAL signal connected at 1.
("AUTO INPUT" is recommended for convenience.)
4. Press the 1/u button to turn OFF the power.
5. Press the 1/u button while pressing the SET UP and SOUND FIELD GENRE buttons to turn ON the power.
6. Perform DSP check in the following sequence to display the results. If no problems, "DSP NO ERROR" will be displayed on the
fluorescent indicator tube, and the reference signals of the 1 KHz internal oscillation will be output to FRONT, REAR, CENTER, and
WOOFER.
Sequence :
1 DSP1 BOOT ERROR CHECK (DSP1:IC1301)
2 DSP1 REPLAY ERROR CHECK
3 DSP2 RAM ERROR CHECK (DSP2:IC1402 RAM:IC1402)
4 DSP2 REPLAY ERROR CHECK
Refer to Table 2 if errors occur and perform the repairs.
Table-2 Display of Errors and Main Causes
Error Message
DSP1 BOOT ERROR
DSP1 REPLY ERROR
DSP2 RAM ERROR
DSP2 REPLY ERROR
7. Each time the < , ∧ , ∨ , or > button is pressed, the display changes between "DSP TEST MODE" and "DSP NO ERROR".
When "DSP TEST MODE" is displayed, the signals input from the external equipment connected at 1. will be assigned to the outputs as
shown in Table 1.
When "DSP NO ERROR" is displayed, the reference signal of the internal oscillation will be output to the FRONT, REAR, CENTER, and
WOOFER channels.
(Each time the < , ∧ , ∨ , or > button is pressed, self-diagnosis will be executed from 3 of step 6.
8. To end, press the 1/u button and turn OFF the power.
Note:
Do not touch other buttons except < , ∧ , ∨ , or > during this mode with a specific purpose.
Messages are displayed in the same way as in normal operations.
Operations itself will not be normal here, therefore if other buttons or knobs are touched by accident and the message is changed, press
the 1/u button to turn OFF the power and exit the mode.
Output To
µ
µ
µ
Possible Cause and Countermeasure
Faulty connection of IC1301, fault around the power supply of IC1301
Fault of peripheral circuit of Pin @º of IC1301
Faulty connection with RAM (IC1402)
Faulty communication with microprocessor, fault of peripheral circuit of Pin !£ of IC1401,
fault around power supply and clock of IC1401
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