STR-DB840, STR-DB940 - Sony Audio Service Manual (repair manual). Page 10

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All fluorescent segments are tested.  When this test is activated,
all segments turn on at the same time, then each segment turns on
one after another.
Procedure:
1. While depressing, the 

[A.F.D.]

 and the 

[DIMMER]

 buttons si-

multaneously, press the power  

`/1

  button to turn on the main

power.

2. All segments turn on at the same time, then each segment turns

on press the 

[A.F.D.]

 button.

All preset contents are reset to the default setting.
Procedure:
1. While depressing the 

[SET UP]

, and the 

[DIMMER]

 buttons

simultaneously, press the power  

`/1

  button to turn on the

main power.  The message Factry Set appears and the present
contents are reset to the default values.

All preset contents are cleared when this mode is activated.  Use
this mode before returning the product to clients upon completion
of repair.
Procedure:
1. While depressing the 

[SET UP]

 button simultaneously, press

the power  

`/1 

  button to turn on the main power. The ma-

chine enters the DEMO mode.
DEMO mode: Wait a while, then the demonstration starts. If
the power  

`/1 

 button is pressed often the demonstration has

started, the power is turned off, and the demonstration resumes
if the power  

`/1 

 button is pressed again.

ALL CLEAR mode; Press the 

[A.F.D.]

, 

[MODE +]

, and

`/1

buttons.

The preset sound field is cleared when this mode is activated.  Use
this mode before returning the product to clients upon completion
of repair.
Procedure:
1. While depressing the 

[MODE +]

 button, press the power

`/1

button to turn on the main power.  The message S.F Initialize
appears and initialization is performed.

Either the 9 kHz step or 10 kHz step can be selected for the AM
channel step.
Procedure:
1. Set the FUNCTION to AM.  Turn off the main power.
2. While depressing the 

[TUNING -]

 button or the 

[PRESET

TUNING +]

 button, press the power  

`/1 

 button to turn on the

main power.

3. Either the message AM 9kHz Step or AM 10kHz Step appears.

Select the desired step.

It tests whether the DSP works correctly or not.  When the DSP
test is activated, the test data is output from the DSP (IC1401:
CXD2712R) of the DIGITAL board and is written in the RAM
(IC1402: IDT71V016S).  When the test data is read from the RAM
by the DSP, the data output must be equivalent to the original data.
If they disagree, an error is triggered.  Errors can be caused by the
broken data line or defective soldering.
Procedure:
1. While pressing the 

[MODE +]

 and 

[DIMMER]

 buttons, press

the

`/1

button to enter the DSP test mode.

2. The message DSP TEST MODE appears.  When an error oc-

curs, the message DSP2 ERROR is displayed.  When there is
no error, the message DSP2 NO ERROR appears and the 1
kHz signal is output to all channels.

3. Use the 

[MUTING]

 button, when selecting the SINE WAVE,

THROUGH, or IMPLUSE mode.

When this mode is used, the microprocessor version number is
displayed.
Procedure:
1. Press the

`/1

button while pressing the 

[MUTING]

, and

[DIMMER]

 buttons to turn on the power. The microprocessor

version number appears as follows.