UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - 3-valve reflex 1925 kit?

PJL · 22nd Jun 2021, 11:57 am

It's reassembled with 2V valves and doing something but mostly squealing and considerably more so with no aerial. I have received a station but I think it was down in the 700KHz area so probably need to do more work on the RF intervalve transformer.

The RF Transformer that came with the set is for a low frequency (between the MW and LW) and seems to be made of identical windings wound in a bifilar manner but the one I am using is from a crystal filter coupling transformer and is not going to be as closely coupled so offering gain and selectivity I do not need. With the original bright emitter valve I could have fiddled with the filament current to adjust the gain but I am not planning on experimenting with the pristine 1924/5 Nelson Multi.

Next stage is to stick a scope on it and see exactly what it's oscillating at then strip some of the wire off the RF transformer secondary.

22nd Jun 2021, 11:57 am	#9
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: 3-valve reflex 1925 kit? It's reassembled with 2V valves and doing something but mostly squealing and considerably more so with no aerial. I have received a station but I think it was down in the 700KHz area so probably need to do more work on the RF intervalve transformer. The RF Transformer that came with the set is for a low frequency (between the MW and LW) and seems to be made of identical windings wound in a bifilar manner but the one I am using is from a crystal filter coupling transformer and is not going to be as closely coupled so offering gain and selectivity I do not need. With the original bright emitter valve I could have fiddled with the filament current to adjust the gain but I am not planning on experimenting with the pristine 1924/5 Nelson Multi. Next stage is to stick a scope on it and see exactly what it's oscillating at then strip some of the wire off the RF transformer secondary.