Ferranti OPM 6 Output Transformer - UK Vintage Radio Repair and Restoration Discussion Forum

RF Burn · 17th Jan 2020, 12:11 pm

Does anyone have any data on the Ferranti OPM 6 push-pull output transformer?

I can see the turns ratios as they are printed on the casing, I assume that these refer to the whole of the primary winding, i.e. 45/1 gives a 6K Anode to Anode impedance when driving a 3 Ohm speaker, which seems likely to be the speaker impedance intended for use with this tranny?

No idea of power rating, primary winding current capability, etc. though.

Thanks,

Adrian

TowerRadio · 17th Jan 2020, 12:29 pm

A bit of info

RF Burn · 17th Jan 2020, 1:07 pm

Many thanks for that info.

The 120H inductance at 100mA does seem a little unbelievable, I have just measured mine, the primary winding is about 400 Ohms total and its inductance @ 1KHz, no DC measures about 20H, unless of course my transformer has shorted turns :-((

Adrian

geeoboeh2s · 17th Jan 2020, 1:10 pm

If you can manage to find a copy the Ferranti book "The true road to radio" provides a lot of useful information of all the Ferranti audio products of this era.

Chris

FIXITNOW · 17th Jan 2020, 1:21 pm

have this

FIXITNOW · 17th Jan 2020, 1:29 pm

and

RF Burn · 17th Jan 2020, 7:04 pm

Many thanks for the info chaps, I think that just about covers everything!

Adrian

17th Jan 2020, 12:11 pm	#1
RF Burn Hexode Join Date: Apr 2008 Location: Ramsgate, Kent, UK. Posts: 252	Ferranti OPM 6 Output Transformer Does anyone have any data on the Ferranti OPM 6 push-pull output transformer? I can see the turns ratios as they are printed on the casing, I assume that these refer to the whole of the primary winding, i.e. 45/1 gives a 6K Anode to Anode impedance when driving a 3 Ohm speaker, which seems likely to be the speaker impedance intended for use with this tranny? No idea of power rating, primary winding current capability, etc. though. Thanks, Adrian

17th Jan 2020, 12:29 pm	#2
TowerRadio Hexode Join Date: Mar 2008 Location: Bristol, UK. Posts: 388	Re: Ferranti OPM 6 Output Transformer A bit of info Attached Thumbnails

17th Jan 2020, 1:07 pm	#3
RF Burn Hexode Join Date: Apr 2008 Location: Ramsgate, Kent, UK. Posts: 252	Re: Ferranti OPM 6 Output Transformer Many thanks for that info. The 120H inductance at 100mA does seem a little unbelievable, I have just measured mine, the primary winding is about 400 Ohms total and its inductance @ 1KHz, no DC measures about 20H, unless of course my transformer has shorted turns :-(( Adrian

17th Jan 2020, 1:10 pm	#4
geeoboeh2s Rest in Peace Join Date: Mar 2010 Location: Berkshire, UK. Posts: 72	Re: Ferranti OPM 6 Output Transformer If you can manage to find a copy the Ferranti book "The true road to radio" provides a lot of useful information of all the Ferranti audio products of this era. Chris

17th Jan 2020, 1:21 pm	#5
FIXITNOW Octode Join Date: Feb 2007 Location: Ely, Cambridgeshire, UK. Posts: 1,975	Re: Ferranti OPM 6 Output Transformer have this Attached Thumbnails

17th Jan 2020, 1:29 pm	#6
FIXITNOW Octode Join Date: Feb 2007 Location: Ely, Cambridgeshire, UK. Posts: 1,975	Re: Ferranti OPM 6 Output Transformer and Attached Thumbnails

17th Jan 2020, 7:04 pm	#7
RF Burn Hexode Join Date: Apr 2008 Location: Ramsgate, Kent, UK. Posts: 252	Re: Ferranti OPM 6 Output Transformer Many thanks for the info chaps, I think that just about covers everything! Adrian