selematic st150/1 (under construction)
A 150-Watt 1 channel XTAL controlled set. Hybrid technology from the early 70's. The output is 2 6DQ6 (or originally 6146's) and the driver is a 6EH7ff. Iwill place a PIC-PLL on this unit, the boards are done....
The face of the Selematic at the beginning of the process
Since there was not provision for RF tunning, I made one, using varicap diode BB119 and using the Gain button on the front panel. The orange wires show the new connections.
The calculation used to redesign the front end and the RF transformers data I will put here as soon as possible.
The main tuning now is using a 10-turn potentiometer, instead of the XTAL. It was easy by just the replacing the XTAL by a proper L-C combination. VFO Stability is not so good, but after the insertion of the PIC-PLL I think it will be improved significantly.