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Transmit/Receive Relay For Dentron GLA-1000B After Conversion To Svetlana EL-509/6KG6 Tubes

Relay is a Midtex part number# 157-13B-200 (12VDC, 10 AMP Contacts, Open frame, 3PDT)

Resistor between #1 and #4 is a 75K OHM 1 Watt and is there to drop the cathode bias.  This cuts the tubes off in stand-by or receive conditions in order to increase the life of the tubes (keeps them cooler when not is use!!!)

***Contact #3 and #5 are connected with a jumper***

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Summary:

IN THE STAND-BY MODE OR IN RECEIVE ZENER CATHODE BIAS IS DROPPED ACROSS THE 75K OHM RESISTOR SHU1TING THE OFF. IDLING PLATE CURRENT IS THEREFORE REDUCED TO A VERY LOW VALUE. IN THE TRANSMIT MODE THE RESISTOR IS OPENED AT CONTACT #1 REMOVING IT FROM THE CIRCUIT. THIS SETS TRANSMIT IDLING PLATE CURRENT TO ABOUT 100 MA.   

IN RECEIVE MODE SIGNALS COME IN FROM ANTENNA VIA CONTACT #3 TO OUTPUT SELECTOR SWITCH (THIS SWITCH IS ONLY ON THE GLA-1000B). FROM THE OUTPUT SELECTOR SWITCH THE INCOMING SIGNAL GOES INTO THE RADIO RECEIVER VIA CONTACT #9 (RF IN).  

IN TRANSMIT THE RF DRIVE GOES INTO CONTACT #9 (HF IN) TO CONTACT #6 (INPUT TO THE FINALS AT THEIR CATHODE (PIN #9). AFI7ER THE TUBES AMPLIFY THE SIGNAL IT GOES INTO CONTACT #3 (OUTPUT FROM TUBES) TO CONTACT #5 (RF OUT) AND ON TO THE ANTENNA SELECTOR SWITCH. THE ANTENNA SELECTOR HAS TWO POSITIONS (I & DL).

***Don't forget to install a 1N4007 diode across the relay's coil connections**  The cathode (band) of the diode is soldered to point (y), =DC, on the schematic** and the anode of the diode is soldered to the -DC side.