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Leon Crampin · 17th Nov 2017, 6:23 pm

Pye in the UK produced the P117 AM/FM superhet with only 3 valves + rectifier. The ECC85 was used as a reflexed RF/IF amplifier + mixer/oscillator on FM and as an oscillator/mixer on AM. IF amplification was furnished by an EBF89, the 2 diodes being used for AM detection and AGC. The FM detector was a couple of Ge diodes and the output stage an ECL82.

It worked passably well, being slightly short of gain on FM and a bit prone to drift. The AM performance was surprisingly good. The ECL82 was not an outstanding performer, the triode being prone to picking up hum. The later ECL86 had much better internal screening.

This design was never repeated. With a multitude of "hot" signal switching, it must have been a nightmare to produce and align. I have one as a curiosity (only). I quite like, for a cheap set, the concept of utilising 6.3V valves with a heater transformer with mains derived HT. The sets run cool without heater-cathode insulation problems or induced hum.

Leon.

17th Nov 2017, 6:23 pm	#22
Leon Crampin Octode Join Date: Nov 2005 Location: Surrey, UK. Posts: 1,874	Re: Most Minimal Superhet Pye in the UK produced the P117 AM/FM superhet with only 3 valves + rectifier. The ECC85 was used as a reflexed RF/IF amplifier + mixer/oscillator on FM and as an oscillator/mixer on AM. IF amplification was furnished by an EBF89, the 2 diodes being used for AM detection and AGC. The FM detector was a couple of Ge diodes and the output stage an ECL82. It worked passably well, being slightly short of gain on FM and a bit prone to drift. The AM performance was surprisingly good. The ECL82 was not an outstanding performer, the triode being prone to picking up hum. The later ECL86 had much better internal screening. This design was never repeated. With a multitude of "hot" signal switching, it must have been a nightmare to produce and align. I have one as a curiosity (only). I quite like, for a cheap set, the concept of utilising 6.3V valves with a heater transformer with mains derived HT. The sets run cool without heater-cathode insulation problems or induced hum. Leon.