Iv - How To Troubleshoot The Power Supply - Sony STR-DE845 Training Manual

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T901's output voltages are dependent upon the match between its resonate frequency and the input frequency
from the oscillator (IC901). When IC901's oscillator frequency is the same as the T901-C916 resonate frequency,
there is maximum power transferred from T901's primary to secondary, producing maximum output voltage
(peak of Figure 9-4's bell curve).
By setting the input oscillator frequency (the Normal Operating Point in Figure 9-4) to above the resonance
point, T901's output voltage can be adjusted by changing the input frequency. The input frequency can be
changed by adjusting the DC error voltage into IC901's oscillator (pin 1). When the normal operating point is
above resonance as shown in Figure 9-4, T901's output voltage is inversely proportional to its input frequency.

IV - How to Troubleshoot the Power Supply

There are three complicated failures that require a troubleshooting plan:
Power Supply is Dead - No voltages
Power Supply will not Power ON - Standby voltage is OK
Output Voltages are Low – One or more voltages are low or high
Refer to Figure 9-5 for the location of grounds and accessible components used for troubleshooting.
D912
C912
820
200V
TH901
DAV C700
POWER BOARD
T901
Output
Figure 9-4 T901
Output Curve
CN904
27V
OUTPUT
COLD
GROUND
D911
D902
R908
HOT
GROUND
C916
FIGURE 9-5 - DAV C700 POWER BOARD
Frequency
CN905
1
11
D909
T901
R902
R903
4
2
5
3
1
SW REG.
IC901
33
9. DAV-C700 Switching Type Power Supply
Normal Operating
Point (200kHz)
OUTPUT
INPUT
P.CONT 1
13V
1
10
6.5V
2
11
P.CONT 2
(DVD ONLY)
3.3V
3
5.6V
4
RESET
9
5.6V - STBY/ON
HEAT SINK=COLD GROUND
PC901
(REG)
PC902
9.5A124 1383
10/19/01

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