Power Supply - Scully 280B Series Instruction And Maintenance Manual

Model 285B
Theory of Operation
assembly back to pln 6 of power amplifier U3 in the play electronics
assembly. The power amplifier raises the level of audio signal to a
level sufficient to drive the headset or an external 8-ohm impedance
sp ~ &ker. The output of U3 is connected to PH ONES jack J133 on the
transport control chassis, then to the SPEAKER OUTPUT terminal block
on the power supply assembly.
When headphones are plugged into the
PH ONES jack, the connection to the speaker is opened.
4.7 POWER SUPPLY
4.8 The power transformer has a tapped primary winding to compensate
for different power sources. The transformer is factory wired for
115-120 volt, 50 / 60 Hz power source. If the reproducer is operated
at a different line voltage, the jumper on the power transformer input
winding should be changed (see Figure 7-3). The output of the power
transformer is applied to a commercial power supply regulator (PSR1).
The regulator has three adjustments which are set at the factory.
They are current limit, overvoltage protection and output voltage
adjust. It is not recommended that the adjustments be changed in the
field except for the possible exception of the output voltage adjust­
ments as explained in Section 6, ELECTRONICS MAINTENANCE.
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