TCS Spot and Monitor Switch Modification
         The TCS equipment does not have any capability to monitor your keying on CW other than to listen to the relay clicking. When changing frequency you can use the MO test function for spotting but when using crystal control there are no provisions for spotting the crystal. With this mod you can simply key the transmitter and do a quick zero beat, spot the transmitter MO or crystal as well as monitor your keying and there is no change to the break in Parts required : DPDT switch and some wire.  

                                                       Click for larger schematic

      The TCS transmitter removes the 225 volts from the receiver tube screens during transmit with transmitter relay K103 (via transmitter pins 11 and 14) and in addition the audio line is grounded by the transmitter relay via transmitter connector pin 9.
     Install a DPDT switch. One half of the switch bypasses the transmitter relay input pins 11 and 14 and provides low B plus direct to pin 3 on the receiver and the other half (but opposite side) of the DPDT switch interrupts the audio path going to pin 9 of the transmitter and prevents it from being grounded by K-103 during transmit.



                       Arrows indicate areas that are effected by the DPDT switch.

                                                         DPDT Switch wiring rear view.

      DPDT switch. Left side switches the receiver screen voltage and is connected to Terminal 1 of L401 for convenience and spot soldered to the receiver pin 3.(Pin 3 all ready has a wire on it). Viewing the switch from the rear, the right side of the switch is used to control the audio. When the transmitter is keyed the receiver audio is normally grounded, you need to lift the wire from pin 9 on the transmitter connector on the power supply and insert a switch between pin 9 and the rest of the pin 9 loop wiring to the other connectors. Switch ON to spot, switch OFF returns the set to normal amateur use.

      Switch ON(up)connects 225 volts from L401 direct to receiver pin 3 and overrides transmitter relay switching. Switch OFF(down) restores normal transmit relay function and the screen voltage will be removed from the receiver during transmit.
      Switch ON (up) disconnects the audio line from transmitter pin 9 and subsequent grounding of the audio line. Switch down restores normal transmit relay function and during transmit the audio is muted by grounding the line.



                 The "Spot" switch mounted in a small enclosure and utilizes existing hardware to
secure it to the chassis. A "No Holes" modification.


                         A spot switch was also added to my homebrew AC supply

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