![]() Design parameters for the input network are 0.66uH for L1 and L2, and 27 pF for the arm capacitance. dia) forming the bridge of the "T," and a 10-75 pF variable capacitor for the arm. The input network is a T-network, with two inductors (8 turns, 1 in. long) isolates the cathode and filaments of the 3Cx800A7. A trifilar-wound filament choke (6.4 uH, 10 turns on 1/2 in. The rebuilt amplier uses a single Eimac 3CX800A7 triode, and features vacuum antenna relays, new metering and control circuits, electronic bias switching, and new forward/reverse power measuring.Ĭircuit Details: The circuit is a conventional cathode-driven (grounded grid) design. deck components were discarded, except the tune and load capacitor, the former being rebuilt (using the few remaining unmelted plates!) to cover 10-30 pF. ![]() I began construction by scrapping the front panel, cabinet top and side panels, and stripping the r.f. Fortunately, blank panels and cabinet parts were available from the original cabinet supplier. ![]() The meter was defective, and an extra hole had been drilled in the front panel. The original Alpha amplifier was missing its two 8874 tubes, and the bandswitch and tuning capacitor had been badly arced and melted. This homebrew six-meter linear amplifier started off life as a "junker" Alpha 76PA h.f.
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