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Full Power Supply
Figure 5
The Full Power supply is located on the Large Signal panel. The Raw B+ voltage from the Input panel
is applied to the Full Power switching transistor, 7301, via Pins 6 and 8 of transformer 5300. This
voltage is protected by Fuse 1300 and filtered by Choke 5330. The Standby line goes Low when the
set is turned On. Transistor 7309 is turned Off, which turns 7300 On. This turns Relay 1305 On.
Startup voltage is applied to Capacitor 2303 via resistor 3300. When 2303 charges to 14.5 volts, the
undervoltage lockout of 7302 connected to Pin 1 is turned On. Drive is output on Pin 3 to the
Switching FET, 7301. This drives 5300 to produce the Full power supply voltages. IC 7302 will
continue to drive 5300 until the charges on capacitor 2303 drop below 9.4 volts. The Under Voltage
Lockout of 7302 will then turn the output on Pin 3 Off until 2303 again charges to 14.5 volts. After
several startup cycles, the operating voltage for 7302 is supplied by Pin 10 of 5300.
Regulation is accomplished by monitoring the 130VS supply via resistors 3324, 3350, 3323 and 3322.
The Feedback voltage is applied to the Shunt Regulator 7304, which drives the Feedback
optoisolator, 7303. The Feedback voltage is applied to Pin 14 of 7302. The voltage is fed to
comparator "C" which is referenced to 2.5 volts. The output of this comparator sets the reference
voltage for comparator "B" which is compared with the voltage on the source of 7301. This voltage is
developed when 7301 turns On, causing current to flow through resistors 3308 and 3309. If 7301 fails,
Resistors 3308 and 3309 should be replaced.
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