Sunday 22 December 2019

Sony STR-DB795 – BIAS adjustment, Factory reset, SBL board schematic

STRDB795 - Sony tuner amplifier - how to adjust the bios voltage, how to set service mode [factory mode]

TUNER FACTORY PRESET
While pressing the [MUSIC] and [PRESET TUNING --] buttons, press the POWER  button to turn on the main power.
The message “FACTORY” appears and the present contents are reset to the default values.
TUNER AM STEP CHANGE (9 kHz/10 kHz) MODE
Either the 9 kHz step or 10 kHz step can be selected for the AM channel step.
Press the Power button to turn on the main power.
Turn the [INPUT SELECTOR] dial to select the “AM”
Press the Power button to turn off the main power.
While pressing the [PRESET TUNING +] or [TUNING +] button,
press the Power button to turn on the main power.
Either the message “9 K STEP” or “10 K STEP” appears.
Select the desired step.
TUNER AUTOBETICAL TUNING MODE (AEP and UK models)
While pressing the [MEMORY/ENTER] button, press the Power button to turn on the main power.
The message “AUTO-BETICAL SELECT” appears and scans and stores all the FM and FM RDS stations in the broadcast area.
When done, the message “FINISH” appears.
SOUND FIELD CLEAR MODE
The preset sound field is cleared when this mode is activated. Use this mode before returning the product to clients upon completion of repair.

While pressing the [2CH] button, press the Power button to turn on the main power.
The message “SF. CLR.” appears and initialization is performed.
FLUORESCENT INDICATOR TUBE PATTERN CHECK MODE
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.
While pressing the [PRESET TUNING --] and [A.F.D.] buttons, press the Power button to turn on the main power.
All segments and [MULTI CHANNEL DECODING] indicator LED turn on.
SHIPMENT MODE
All preset contents are cleared when this mode is activated. Use this mode before returning the product to clients upon completion of repair.
While pressing the [PRESET TUNING --] and [SURR BACK DECODING] buttons, press the Power button to turn ton the main power.
The message “CLEARING” appears and memories are reset to the default values and the main power turn off automatically.
SWAP ALL MODE
While pressing the [PRESET TUNING +] and [A.F.D.] buttons, press the Power button to turn on the main power.
The message “SWAP” appears.
COMMAND MODE CHANGE MODE
The command mode of the remote-commander which this set receives can be changed.
While pressing the [INPUT MODE] buttons, press the Power button to turn the main power.
Either the message “C.MODE.AV1” or “C.MODE.AV2” appears. Select the desired mode.
VERSION CHECK MODE
The version of the micro computer displayed.
While pressing the
[PRESET TUNING --] and [2CH] buttons, press the Power button to turn the main power.
The version of the micro computer and model destination are displayed.
DECODE AUTO ALL MODE
While pressing the [PRESET TUNING --] and [MOVIE] buttons, press the Power button to turn the main power.
The message “DEC TEST” appears.
PROTECTOR AUTO OFF
When this mode is used, a protector on state is maintainable.
While pressing the [PRESET TUNING +] and [MOVIE] buttons, press the Power button to turn on the main power.
The message “PROT EVER” appears.
BIAS ADJUSTMENT
Condition:
input signal: no signal (no load).  Volume: Minimum
Connection
Connect a digital voltmeter to the CN432 (CN482, CN532, CN582, CN632, CN682) on the MAIN board or CN732 on the SBL board.
Press the Power button to turn on the main power.
Adjust the RV431 (RV481, RV531, RV581, RV631, RV681) on the MAIN board or RV731 on the SBL board so that the digital voltmeter reading is 15±2 mV.
[When the adjusting voltage is higher than 15±2 mV, adjust the voltage to the minimum voltage.]
SBL board schematic
Main board adjustment locations

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