7
The output of the amplifier is a Pi-L circuit. The ceramic capacitor for TUNE and LOAD are divided. This
enables the amplifier to be tuned exactly and makes it possible to easily return to the previously set
positions after band changes.
Top view on the opened
Tetrode FU728F Antenna Switch
Blower Power Supply Board
Switch-ON Board
Output Pi-L Circuit
Tuning Capacitor Subpanel HV transformer
3.2.
Power Supply
Power amplifier is using one 3 KVA toroidal transformer. A soft start is provided using relays and
resistors (placed on the switch-ON board). The high voltage is made by combining 4 x 530V AC (total
abt. 2950V DC) @ 1.2A. Each has its own rectifier and filter. In the high voltage circuit, safety resistors
are employed to protect the amplifier against overload (placed on the power supply board).
The separated supply for screen grid is regulated by stabilization with MOSFET and delivers abt. 330V
DC at 100mA. Control grid voltage is also stabilized (-120V DC). Change of stabilized first grid voltage
is controlled by the software (EBS for example).
Summary of Contents for OM2000+
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