Testing The Power Supply Unloaded - Sony STR-DE845 Training Manual

• Remains at 0V - CPU IC901 on the DVD board is not outputting this power ON command.
• Goes to 4.7Vdc - the problem is on this power supply board. Go to step 11.
11. Use Figure 9-5 to locate D912/Anode and measure its voltage. A normal 13Vdc when P Cont 1 is HIGH
(powered ON) means the regulator parts are defective. Check or replace IC902, D912 and PC901. If you
measured 0Vdc at D912/Anode, Q905 or Q908 is defective.
Output Voltages are Low in the Power ON Mode
•
One voltage missing - If one output voltage were missing, you would troubleshoot that output line for a dead
short in the load or an open in the source voltage line.
•
One or more power supply voltages missing - When one or more power supply output voltages are low, the
problem is either an excessive load or the power supply cannot deliver the normal current. Use Chart 9-5 to
determine if the load is within the normal range.
Output Voltage
27V CN904/pins 1 and 2
13Vdc CN905/pin 1
6.4Vdc CN905/pin 2
3.3Vdc CN905/pin 3
5.6Vdc CN905/pin 4
The wires from CN905 may be removed for current tests by lifting the plug's wire holder.
•
All T901 voltages are LOW or HIGH - If ALL the T901 power transformer output voltages are proportionally
low or high, the regulating stage or the basic power supply cannot deliver the voltage or normal current. Use
Chart 9-6 (steps 1-3 along the top) to help determine which of these stages is not operating properly.
1. Power ON and measure
CN904/pin 1 voltage
27V Output Voltage=
Higher than normal
27V Output Voltage=
Lower than normal
•
PC901/pin 3 voltage is normal - If the voltage at PC901/pin 3 is a normal 7.5Vdc (Chart 9-6, step 2),
either: 1) test the power supply unloaded in the next section; or 2) follow the troubleshooting steps in
"Power Supply is Dead" because the supply may be partially in the standby mode causing the low output
voltages.
V - Testing the Power Supply Unloaded
You can run this power supply unloaded to determine if the power supply could generate a voltage, but the output
voltages will be a little higher than normal.
1. Unplug both output connectors CN904 and CN905.
2. Connect CN905 pin 4 to pin 10. Caution: When counting pins, the second pin has no number so the pin
complement of connector CN905 is: 1, X, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11. When in doubt, count from pin 11 to the
pins you want. Connecting pins 4 to 10 places the standby voltage into the power ON line.
Chart 9-5 – Power Supply Load Current
Location Tuner Mode
367 ma
200 ma
823 ma
2.6 ma
70 ma
Chart 9-6 - Troubleshooting for Incorrect Output Voltages
2. Measure PC901/pin 3 (use HOT
gnd). Typical voltage is 7.5Vdc
This voltage is Higher
This voltage is Lower
This voltage is Higher
This voltage is Lower
9. DAV-C700 Switching Type Power Supply
Video Mode
367 ma
227 ma
843 ma
2.5 ma
70 ma
Basic Power supply IC901, T901, C916
Error regulator parts about IC902, PC901
Error regulator parts about IC902, PC901
Basic Power supply IC901, T901, C916
35
DVD Mode
367 ma
581-1,200 ma
823 ma
446 ma
82 ma
3. Suspect