At a plate voltage of 28 volts, the tubes perform poorly compared to solid state devices. Conversion to solid state reduces heat and load current due to filament requirements.
These changes are from way back in 1975.
A. Conversion of Linear AF Stages
2. Phase Inverter and Second AF Amplifier
Note: V601 filament is in series with V606 and V607. 26A7 replacement should use a newer darlington NPN transistor and design more like described in
Ham Radio Magazine,
April 1976, page 65.
The current of V607 replacement is much too low. Gain varies widely at such low currents.
2. First AF Amplifier
Note: V601 filament is in series with V606 and V607.
The current and gain of V606 replacement is much too low. Gain varies widely at such low currents.
B. Conversion of Non-linear Stages
1. First and Second Mixer
2. Detector and Noise Limiter
NOTE: V602 and V603 filaments are in series.
3. RF and IF AGC Rectifier
NOTE: V601A is the IF Cathode follower which would be disabled if V601 is removed. V601 filament is in series with V606 and V607. V602B is the Squelch Rectifier.
4. Squelch
C. Calibrator Circuits
1. 200 KC Crystal Oscillator
Pierce electron coupled circuit. Would probably need two transistors to realize this conversion.
Hi-res schematic
2. Multivibrator
3. Harmonic Amplifier and Distorter
Hi-res schematic
D. Conversion of Oscillators and Control Stages
1. Crystal Oscillators (Proposed)
Colpitts crystal oscillators.
NOTE: V401 and V402 filaments are in series.
