Dav-C700 Switching Type Power Supply; Safety For You And The Circuit; Ii - Power Supply Operation - Sony STR-DE845 Training Manual

DAV-C700 Switching Type Power Supply

This switching power supply description and troubleshooting currently applies to these three Sony models:
•
DAV-S500 (HCD-S500)
•
DAV-C700 (HCD-C700)
•
DAV-C900 (HCD-C900)
Switching Power Supply Advantages
Although switching power supplies have the disadvantage of containing more parts than a 60 Hz. power transformer
supply, the following advantages listed in Chart 9-1 outweigh this disadvantage:
1. Low cost (much cheaper power transformer)
2. Lightweight (small transformer)
3. Excellent voltage output stability (regulation)
Concerns and Procedures
With switching power supplies, new safety concerns, circuit details and repair procedures are divided into the
following sections:
•
Safety for both you and the circuit
•
Power supply operation
•
Power supply regulation
•
How to troubleshoot the power supply
•
Testing the power supply unloaded
•
Troubleshooting shortcuts
I - Safety for You and the Circuit
•
When repairing products with pulse power supplies, you MUST use an isolation transformer for technician,
test equipment and product safety. The external isolation transformer just prevents immediate damage to
your instruments and the product.
•
In the power supply circuitry there is a HOT ground that is connected to one side of the AC line and a COLD
ground that is often the same as chassis or speaker ground, isolated from the AC line. Use the correct
ground when measuring voltages.
•
Lethal voltages are still present during troubleshooting so caution must be observed.
II – Power Supply Operation
This section is divided into the following topics:
•
Power Supply Control – what turns it ON/OFF
•
Switching Power Supply Block – Overall operation
•
Power Supply Operation – Standby Mode
•
Power Supply Operation – Power ON Mode
Chart 9-1 - Advantages of Switching Power Supplies
9. DAV-C700 Switching Type Power Supply
4. Lower heat generated (higher efficiency)
5. Small or same size
6. Can operate over wide input voltages.
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