Wireless of the Week - week 22

[Jesse Browning]

I could email you a better picture of the wiring diagram. The speaker I have only has two terminals. The only WWII picture I have of a speaker in a sexton shows only two terminals. I wonder if that would exclude its use with the radio?

[Chris Suslowicz]

Originally Posted by Jesse Browning

I could email you a better picture of the wiring diagram. The speaker I have only has two terminals. The only WWII picture I have of a speaker in a sexton shows only two terminals. I wonder if that would exclude its use with the radio?

No, if the Sexton has only two terminals, then it's only for use with the WS19 (I think).

Control Unit 190 is a bit complicated (well, they all got bit complicated when the rebroadcast facility was added), but I'm getting there.

The top (3 terminal) tagstrip is for Driver Intercom, and has Speech, Mic+ and Ground.

The next tagstrip (2 terminal) is for the loudspeaker connection.

The switch has 3 wafers with 3 sets of contacts on each; from left to right (as shown on the wiring plate):

1) Loudspeaker Return - connected to ground in all positions.

2) Loudspeaker Feed - selects source via 5, 7 & 8

3) not used

4) Feeds set audio into the intercom amplifier via a resistor (this is probably the 5,600 ohm resistor, because the contacts are connected to the A and B set Tel+ output (i.e. phones) and the wiper goes via the resistor to the intercom Mic+ connection).

5) 'A' set feed if rebroadcast selection set to A&B when on IC (I think).

6) not used

7) 'B' set set feed if rebroadcast selection set to A&B when on IC (I think).

8) Set selection to Speech (intercom output) line. Centre position shorts out a resistor - this will be the low value (270 ohm) one, I think, to compensate for the loudspeaker being disconnected.

9) 'A' set unattended line - connects this to ground if the loudspeaker is switched to 'B', so that the red lamp will light if the operator's droplead is also switched to 'B', indicating that nobody is monitoring the 'A' set output.

I think that's how it all works!

Chris.

[Jesse Browning]

Sounds right. I installed the radio last year, but can only listen to it through the tannoy. Im in the process or rebuilding the 4 headsets used in the vehicle so the intercom can be utilized.

[David Dunlop]

Chris.

In Bruce's first post on this thread, last photo, the image is the information plate inside the cover. The section dealing with the loudspeaker states the two terminals marked '19-Set' are connected to windings of 30 ohm value to match the output from the I/C amp in the 19-Set, if that helps at all.

David

[Chris Suslowicz]

Originally Posted by David Dunlop

Chris.

In Bruce's first post on this thread, last photo, the image is the information plate inside the cover. The section dealing with the loudspeaker states the two terminals marked '19-Set' are connected to windings of 30 ohm value to match the output from the I/C amp in the 19-Set, if that helps at all.

David

It does.

The loudspeaker is obviously a rather heavier load than a couple of headsets, so needs to connect to the IC amplifier rather than one of the set outputs.

The Control Unit 190 is an odd beast with a single droplead for the wireless operator, so everybody else must be using the intercom - either via Junction Distribution boxes (No.3 or No.4 because the Mic+ line feeds into the IC amplifier so it can't be for the power microphone) or the loudspeaker (presumably once the gun is deployed).

Chris.

[Jesse Browning]

Does anyone have a 4 terminal Tannoy they would part with?

[JRRDixon]

What is the average price of the loudspeakers. Original paint complete. No strap. All lock hasps there. Original marking with stamp. Arrow with p beside it. Getting rid of a pair but don't want to rip anyone off.

Jason