Page
7
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18
Top view on the opened OM4000 HF
Tetrode
FU728F PWR meter
Blower Switch-on board
Output Pi-L Circuit
Tuning capacitor
Power supply board
Subpanel
3.2. Power Supply
Power supply of the amplifier is comprised of two of 3 kVA toroidal transformers. A soft start
is provided using relays and resistors.
The high anode voltage is made by combining 8 x 420 V (total 3360V) @ 2.5A. Each has its
own rectifier and filter. In the high voltage circuit, safety resistors are employed to protect the
amplifier against overload.
The source for screen grid is regulated by parallel stabilization with BU941 NPN Darlington
transistors and delivers a voltage of 350V at 200mA. The -120V for the control grid is
regulated with Zener
diodes.
