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5. Power supply test
1. Make sure that you are using proper
voltage for testing transformer
2. Disconnect backboard and preamp board.
3. Check the fuses F2A, F3A with ohmme-
ter. When fuse is broken exchange it only
with same type (2A/250V). Do the same
with F4A, F5A (8A/250V). If new fuse
immediately burns after switching on the
power then power supply with power
amp is damaged and need to be ex-
change.
4. Connect power cable, turn on the power
switch
5. Measure DC voltage on resistors shown
on pictures on the left. Voltage values
should be +90V between yellow and red
point, and -90V between green and red
point. Those values are correct only
without any load on the speaker output.
It can drop to ±77V when power amp is
fully driven.
6. Measure DC voltage on the connector.
Voltage values should be +15V between
red and green AGND point, and -15V
between yellow and green AGND point.
Output load should not change those
voltages.
7. If transformer is ok (checked in
transformer test) but measured voltages
are different than given values (tolerance
is ±10%) or one of measured voltages is
equal zero then power amp with power
supply need to be exchange.
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