Wireless of the Week - week 22

[Chris Suslowicz]

Originally Posted by Jesse Browning

The sexton has a 190 control box tapped for wires that run through the vehicle conduit to the speaker at the front of the crew compartment.

Looking at the Parts Identification List (FZ256/3), the 190 is very similar to Control Unit No.3 (A or B), except that there's an extra 270 ohm resistor somewhere on the top switch, and a 3-way tag board in place of the usual 4-way one in the top box. I suspect the resistor is connected in series with the feed to the loudspeaker terminals to limit the load on the WS19 output transformers and make it look a bit more like a set of headphones. There does not appear to be a volume control anywhere in the system, nor any facility for intercom use - the loudspeaker is output only by the look of it from the component listing.

Chris.

[Jesse Browning]

Chris; does your reference give the values of the different resistors? I made a No.190 box out of a No 3 box using the wiring diagram on the lid of the main electrical junction box in the radio compartment. It doesnt give the value of the resistors. What I would prefer is an original No.190 box.

[Chris Suslowicz]

Originally Posted by Jesse Browning

Chris; does your reference give the values of the different resistors? I made a No.190 box out of a No 3 box using the wiring diagram on the lid of the main electrical junction box in the radio compartment. It doesnt give the value of the resistors. What I would prefer is an original No.190 box.

Ah, there are actually two resistors on the top switch, and 4 on the Normal/Rebroadcast switch (those are identical on 3A, 3B and 190).

The two new ones on the 190 are

17 - 1/4 W. Metallized 5,600 ohms +/- 10%
19 - 1/2 W. metallized 270 ohms +/- 10%

(Numbers are on the parts layout drawing, not component numbers.)

I wonder if there's a circuit diagram for that box in the other EMERs.

More later...

...sorry, we don't appear to have a circuit diagram of the control unit with component values. It's not in the 'First Echelon Work" EMER, which is all about operator and electrician maintenance, and the "2nd - 4th Echelon Work" just covers the set internals in extreme detail - nothing about control units.

Chris.

[Jesse Browning]

[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.