Ferranti Nova 1935 Restoration. - UK Vintage Radio Repair and Restoration Discussion Forum

Colin Boggis · 29th Sep 2017, 7:39 pm

I'm now starting to restore this old beast but have come across a possible error in the service data. The DC resistances of the oscillator coils L9,10.11 & 12 are causing concern. I believe L9 & L11 are MW, L10 & 12 LW. Service data gives L9 4 ohms, L10 25 ohms which makes sense, the LW winding having many more turns. But L11 is shown as 6.5 ohms & L12 as 3.2 ohms. This appears to be reversed. Can anyone clarify this? Am I missing something or is the data incorrect? I cannot simply check the connections as the original wiring was so poor that I just stripped it all out and am starting again from scratch. (I wish I hadn't been so quick to do that! But too late now.)

ms660 · 29th Sep 2017, 7:48 pm

Some oscillator coils in some receivers were wound with resistance wire (reaction/feedback coils) I seem to remember.

Looking at a couple of different service sheets for the Nova seems to indicate that the MW feedback coil is a higher resistance that the LW feedback coil

Lawrence.

Colin Boggis · 2nd Oct 2017, 8:39 am

Yes I've noticed several service sheets show the same, but think this may be because they are all prepared from a common source?
I wondered if anyone has a Nova and could check actual values? A long shot I guess, but I live in hope. In the meantime I'll continue with the rebuild but leave those coil connections until later. If necessary trial & error should resolve the issue for once & for all.

Colin Boggis · 2nd Oct 2017, 8:41 am

ms660 - sorry I just realised the significance of your comments regards resistance wire - the 2 coils in question are indeed reaction coils, so perhaps the stated values are indeed correct. Thanks for this important info.

29th Sep 2017, 7:39 pm	#1
Colin Boggis Pentode Join Date: Jun 2008 Location: Christchurch, Dorset, UK. Posts: 237	Ferranti Nova 1935 Restoration. I'm now starting to restore this old beast but have come across a possible error in the service data. The DC resistances of the oscillator coils L9,10.11 & 12 are causing concern. I believe L9 & L11 are MW, L10 & 12 LW. Service data gives L9 4 ohms, L10 25 ohms which makes sense, the LW winding having many more turns. But L11 is shown as 6.5 ohms & L12 as 3.2 ohms. This appears to be reversed. Can anyone clarify this? Am I missing something or is the data incorrect? I cannot simply check the connections as the original wiring was so poor that I just stripped it all out and am starting again from scratch. (I wish I hadn't been so quick to do that! But too late now.)

29th Sep 2017, 7:48 pm	#2
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Ferranti Nova 1935 Restoration. Some oscillator coils in some receivers were wound with resistance wire (reaction/feedback coils) I seem to remember. Looking at a couple of different service sheets for the Nova seems to indicate that the MW feedback coil is a higher resistance that the LW feedback coil Lawrence. Last edited by ms660; 29th Sep 2017 at 8:12 pm. Reason: addition

2nd Oct 2017, 8:39 am	#3
Colin Boggis Pentode Join Date: Jun 2008 Location: Christchurch, Dorset, UK. Posts: 237	Re: Ferranti Nova 1935 Restoration. Yes I've noticed several service sheets show the same, but think this may be because they are all prepared from a common source? I wondered if anyone has a Nova and could check actual values? A long shot I guess, but I live in hope. In the meantime I'll continue with the rebuild but leave those coil connections until later. If necessary trial & error should resolve the issue for once & for all.

2nd Oct 2017, 8:41 am	#4
Colin Boggis Pentode Join Date: Jun 2008 Location: Christchurch, Dorset, UK. Posts: 237	Re: Ferranti Nova 1935 Restoration. ms660 - sorry I just realised the significance of your comments regards resistance wire - the 2 coils in question are indeed reaction coils, so perhaps the stated values are indeed correct. Thanks for this important info.