Vi - Troubleshooting Shortcuts - Sony STR-DE845 Training Manual

3. Plug the unit into AC and press the front panel Power ON switch so it latches in. The power supply should
start and produce the following voltage. See Chart 9-7 below:
Chart 9-7 - No Load Power Supply Output Voltages – Use Cold Ground
Location
CN904/pin 1, 2
CN905/pin 1
CN905/pin 2
CN905/pin 3
CN905/pin 4

VI - Troubleshooting Shortcuts

Because the circuit board is dense, access to some parts is difficult or impossible from the top of the board.
Temporally changing circuit conditions to see if some circuit groups work in this power supply is a good way to
speedily arrive at the non-working part. These shortcuts do not replace a complete troubleshooting plan.
Purpose
See if CPU pwr ON
command arrives at
PC902
See if CPU pwr ON
command finally
arrives at IC901/pin
4.
See if CPU pwr ON
command also
enables the
regulating circuit
(cancels the Stby
Mode).
PS. Shorting pins of PC901 (regulating circuit) will cause IC901's oscillator to stop until power is removed (no
damage will result). The power supply's 27V output line will momentarily rise from 19V to 38Vdc when pins 1-
2 are shorted, or decay toward 0 when pins 3-4 are shorted.
Caution: Never cause the power supply output to go to a maximum of 38Vdc while connected to the load.
No Load Voltage
27-29Vdc
14.3Vdc
6.8Vdc
0V *
5.6Vdc
* 3V will output if a HIGH is also placed at CN905/pins 10 & 11.
Chart 9-8 - Shortcut Procedures
Conditions
Standby Mode (front
panel button in)
Standby Mode – Release
front panel Pwr to turn
OFF unit, then press
button in again.
Standby Mode – Release
front panel Pwr to turn
OFF unit, then press
button in again.
9. DAV-C700 Switching Type Power Supply
Normal Power ON Voltage
27Vdc
13.6Vdc
6.4Vdc
3.3Vdc
5.6Vdc
Procedure Normal Result
Press the Play Voltage at
or an Eject PC902/pin 2
button to power should change
ON. from 4.7V to
5.6V
Short Voltage at
PC902/pins 1 IC901/pin 4
and 2 together. should change
from 11V to 20V.
Press the Play Voltage at
or an Eject D912/Cathode
button to power (band) should
ON. change from
14.8V to 28V
36
Parts Tested
Stby voltage,
IC907, Q915, Pwr
ON Path from
CPU (DVD bd.).
Q901-Q903,
D903, PC902
D917, Q905,
Q908.