Sony STR-DE845, Руководство по обучению

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9. DAV-C700 Switching Type Power Supply
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Remains at 0V - CPU IC901 on the DVD board is not outputting this power ON command.
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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
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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.
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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.
Chart 9-5 – Power Supply Load Current
Output Voltage Location Tuner Mode Video Mode DVD Mode
27V CN904/pins 1 and 2 367 ma 367 ma 367 ma
13Vdc CN905/pin 1 200 ma 227 ma 581-1,200 ma
6.4Vdc CN905/pin 2 823 ma 843 ma 823 ma
3.3Vdc CN905/pin 3 2.6 ma 2.5 ma 446 ma
5.6Vdc CN905/pin 4 70 ma 70 ma 82 ma
The wires from CN905 may be removed for current tests by lifting the plug’s wire holder.
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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.
Chart 9-6 - Troubleshooting for Incorrect Output Voltages
1. Power ON and measure
CN904/pin 1 voltage
2. Measure PC901/pin 3 (use HOT
gnd). Typical voltage is 7.5Vdc
3. Suspect
This voltage is Higher Basic Power supply IC901, T901, C916 27V Output Voltage=
Higher than normal
This voltage is Lower Error regulator parts about IC902, PC901
This voltage is Higher Error regulator parts about IC902, PC901 27V Output Voltage=
Lower than normal
This voltage is Lower Basic Power supply IC901, T901, C916
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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.