Stentorian S36 ext.loudspeaker - UK Vintage Radio Repair and Restoration Discussion Forum

Daventry 5XX · 23rd Feb 2013, 9:33 pm

Hi All

I'm looking for some info.on a Stentorian S36 L/S.(circa 1936)

I purchased one at an auction with the intention of using it with a Cossor 334 TRF set (1932) if compatible.

It came with what appeared to be a very perished 1930's style twisted braid power cord which suprised me somewhat as I was expecting just 2 wires for the loudspeaker connections.

Inside there appears to be an energising coil,which would mean it needs an high voltage supply to power it and also an array of adjustable switches and 5 screw terminals marked A B C D & E. D&E being the volume control connected to a variable pot. on the side of the cabinet.

Visually the cabinet looks identical to a KB72 but the innards are completely different.

Do I need to put a high voltage supply on it to get it to work?

Does anyone have a circuit diagram for this beast or any knowledge on how to get it working?

regards

Alan

Tractorfan · 24th Feb 2013, 9:38 am

Hi,
I have a Stentorian speaker here with a permanent magnet and was similarly puzzled by all the connections. Essentially there is a transformer within that can be configured in various way to suit different receivers.
It can be connected for low impedance for sets with an output transformer, high impedance for sets without (these usually drive a moving iron speaker), or as a push-pull output transformer (hence the three wires). So, in its day, it would most likely have HT running through it.
If your radio set uses a normal moving coil speaker, then the low impedance setting should work OK.
Hope this helps.
Cheers, Pete

AC/HL · 24th Feb 2013, 12:17 pm

If the speaker is an energised type (i.e. does not have a permanent magnet) it is unsuitable for a battery set as it stands.
Some have high resistance energising coils, and are energised by being connected across the HT supply. Others have low resistance coils and are energised by being used in place of a smoothing choke in series with the HT line.
Either type could be used with an external power supply but this is not how they were intended to be used, domestically at least.

Daventry 5XX · 24th Feb 2013, 12:31 pm

Hi Pete

The Cossor 334 does not have its own L/S, it has to use an external one which is connected across the HT and the anode of the output valve,I would therefore assume that the cord that looks like a power supply cord would be connected across these two points and connected to the high impedance connections at the L/S end.

Does this sound reasonable to you?

Regards

Alan

PJL · 24th Feb 2013, 2:56 pm

I suggest you post a picture of the speaker. The Cossor needs a high impedance speaker. If ABCDE are taps on a seperate transformer then choose the pair with the highest resistance. If it simply takes the energising speaker coil out on the cable then you will need to provide some DC current by running the HT through the coil or providing a seperate supply.

23rd Feb 2013, 9:33 pm	#1
Daventry 5XX Pentode Join Date: Dec 2011 Location: Daventry, Northamptonshire, UK. Posts: 163	Stentorian S36 ext.loudspeaker Hi All I'm looking for some info.on a Stentorian S36 L/S.(circa 1936) I purchased one at an auction with the intention of using it with a Cossor 334 TRF set (1932) if compatible. It came with what appeared to be a very perished 1930's style twisted braid power cord which suprised me somewhat as I was expecting just 2 wires for the loudspeaker connections. Inside there appears to be an energising coil,which would mean it needs an high voltage supply to power it and also an array of adjustable switches and 5 screw terminals marked A B C D & E. D&E being the volume control connected to a variable pot. on the side of the cabinet. Visually the cabinet looks identical to a KB72 but the innards are completely different. Do I need to put a high voltage supply on it to get it to work? Does anyone have a circuit diagram for this beast or any knowledge on how to get it working? regards Alan

24th Feb 2013, 9:38 am	#2
Tractorfan Dekatron Join Date: Mar 2008 Location: St. Frajou, l'Isle en Dodon, Haute Garonne, France.(Previously: Ellesmere Port, Cheshire, UK.) Posts: 3,183	Re: Stentorian S36 ext.loudspeaker Hi, I have a Stentorian speaker here with a permanent magnet and was similarly puzzled by all the connections. Essentially there is a transformer within that can be configured in various way to suit different receivers. It can be connected for low impedance for sets with an output transformer, high impedance for sets without (these usually drive a moving iron speaker), or as a push-pull output transformer (hence the three wires). So, in its day, it would most likely have HT running through it. If your radio set uses a normal moving coil speaker, then the low impedance setting should work OK. Hope this helps. Cheers, Pete __________________ "Hello?, Yes, I'm on the train, I might lose the signal soon as we're just going into a tunn..."

24th Feb 2013, 12:17 pm	#3
AC/HL Dekatron Join Date: Nov 2003 Location: Heckmondwike, West Yorkshire, UK. Posts: 9,642	Re: Stentorian S36 ext.loudspeaker If the speaker is an energised type (i.e. does not have a permanent magnet) it is unsuitable for a battery set as it stands. Some have high resistance energising coils, and are energised by being connected across the HT supply. Others have low resistance coils and are energised by being used in place of a smoothing choke in series with the HT line. Either type could be used with an external power supply but this is not how they were intended to be used, domestically at least.

24th Feb 2013, 12:31 pm	#4
Daventry 5XX Pentode Join Date: Dec 2011 Location: Daventry, Northamptonshire, UK. Posts: 163	Re: Stentorian S36 ext.loudspeaker Hi Pete The Cossor 334 does not have its own L/S, it has to use an external one which is connected across the HT and the anode of the output valve,I would therefore assume that the cord that looks like a power supply cord would be connected across these two points and connected to the high impedance connections at the L/S end. Does this sound reasonable to you? Regards Alan

24th Feb 2013, 2:56 pm	#5
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Stentorian S36 ext.loudspeaker I suggest you post a picture of the speaker. The Cossor needs a high impedance speaker. If ABCDE are taps on a seperate transformer then choose the pair with the highest resistance. If it simply takes the energising speaker coil out on the cable then you will need to provide some DC current by running the HT through the coil or providing a seperate supply.