Wireless of the Week - week 22

[Jesse Browning]

Super! Thanks!

[Jesse Browning]

The pictures are better than that on my phone and tablet but lose clarity when put on photobucket

[Jesse Browning]

Above the top switch, under the heading "LOUDSPEAKER" are "A","OFF", B. So clearly the loudspeaker was used for the 19 set.

[Chris Suslowicz]

Originally Posted by Jesse Browning

Above the top switch, under the heading "LOUDSPEAKER" are "A","OFF", B. So clearly the loudspeaker was used for the 19 set.

Yes, I'm trying to work out the switching arrangements. (In order to determine which resistor goes where, and what their purpose is.) There appears to be a feed from the 'Speech' line as well, presumably to add the intercom audio to the loudspeaker output.

Has anyone got the circuit diagram of the loudspeaker? (I assume the terminals connect to different tappings on the matching transformer, or the WS19 terminals bypass the push button/capacitor arrangement used with the telephone system.)

More in a while....

Chris.

[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.