UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - 4 Metre Converter

runner_bean · 4th Dec 2017, 12:34 pm

Well I've traced the whole of the 4m converter circuit now, and it all makes sense, and hopefully will work again, subject to me replacing at least one of the Nuvistor valves, which has lost a leg, and rigging up a power supply.

The local oscillator is based on an FT-243 7.550MHz crystal in a Squier overtone circuit using one half of a CV4031/ECC91 double triode (producing 22.65MHz) with the other half wired as a multiplier (presumably 2x). So the LO frequency is 45.3MHz and the IF 25MHz. But this is a bit speculative as I don't have the coil design details and I don't want to dismantle the screening cans as they break easily.

4th Dec 2017, 12:34 pm	#18
runner_bean Triode Join Date: Oct 2017 Location: Suffolk, UK. Posts: 10	Re: 4 Metre Converter - but which design? Well I've traced the whole of the 4m converter circuit now, and it all makes sense, and hopefully will work again, subject to me replacing at least one of the Nuvistor valves, which has lost a leg, and rigging up a power supply. The local oscillator is based on an FT-243 7.550MHz crystal in a Squier overtone circuit using one half of a CV4031/ECC91 double triode (producing 22.65MHz) with the other half wired as a multiplier (presumably 2x). So the LO frequency is 45.3MHz and the IF 25MHz. But this is a bit speculative as I don't have the coil design details and I don't want to dismantle the screening cans as they break easily.