Circuit Board Assembly Hints

(NOTE: Always confirm component values before installing on Circuit Board)

 

Assemble the VFO Board First:

  1. Carefully mount all parts. Watch polarity of the Varactor Diode.( Flat side faces the green trimmer capacitor). Also make sure the exposed lead from the trimmer goes to the grounded solder pad.
  1. Visually inspect for shorts, etc – use magnifying glass.
  2. If using the 10 turn potentiometer, temporarily connect leads to it from the potentiometer terminals on the VFO board.
  1. Set up 12V supply in series with a millimeter. Set for 100 ma. scale.
  2. Apply voltage to board. Current should be about 14-16 ma. (If you get a sudden high current immediately remove power and inspect for solder overflow or a reversed diode)
  3. Check that you have about 6V at the 6 volt zener and 9V at the 9 volt zener diode junction.
  1. Listen on a communications receiver in low end of 40 meter band.
  2. Turn tuning potentiometer all the way left (lowest freq)
  3. Find signal on communications receiver – it may be out of band.
  4. Adjust trimmer until you get lowest desired frequency above 7.000Mhz

(This adjustment is touchy – be patient, and move bit by bit.)

  1. Turn tuning control to right to see that frequency moves up and how far up the band based on the resistor in series with the low end of the control. With 10K you should tune up about 100KHz. from where you set the lowest frequency with the trimmer.

 

Assemble the Main Circuit Board:

 

  1. Mount the three IC holders. Note the dot and number 1 pin go to the left when looking at the top of the board with the torroid on the rignt top. Immediately use an ohm meter to check for shorts between any of the socket pins.
  1. Wind the torroid coil and mount it. Mount the trimmer and the 180 pf capacitor. At this point one can temporarily insert a 1500 ohm resistor in the Mixer Chip socket at pins 1 and 2, and with a VSWR analyzer connected to the coil link, adjust the trimmer capacitor for resonance at about 7.050 MHz.
  1. Now proceed with installing components in the upper part of the board. Carefully note that you have 4.7K resistors where needed and not 47K. Also beware that the 1 Meg. resistor and 510 ohm have similar colors but in reverse direction. Make sure R4 is 1 meg. The receiver will not work if R4 is a low value.
  1. Proceed with installing all the solder-in passive components
  2. Install the 5 volt regulators, but not the transisitors at this point.
  3. After all components except transistors and IC’s are in place, apply power to the board using the milliameter in series with the supply. Current should be about 14 ma. . Now check for 5 volts at the two voltage regulator zenor diodes.
  1. If all looks good solder in all transistors and put IC’s in socket.
  2. Again apply power and current should be around 30 ma.
  3. Now install the two board jumber wires – one for receiver RF injection, and the other for keying the transmitter from Q2 a 2N7000. (See the jumper wire drawing in your drawing package)
  4. Solder in all wires for external connection to volume control, key and receiver audio. (See Drawing Showing Connections)

 

 

Preliminary Testing:

  1. Connect the VFO to the Main board. (rf in, ground, +12.V ). There is a soldering pad on the main board to pick up 12V. for the VFO.
  2. Put a 50 ohm load on the antenna terminals. If you have an RF probe or low power watt meter connect it to the antenna.
  1. Apply power to the assembly. Standby current should be about 40 ma..
  2. Key the transmitter. Current should go over 100 ma. Check for RF output on the probe or wattmeter.
  1. Monitor transmitter in your communications transceiver for tone and frequency.
  1. If you have a signal generator, hold the output near the torroid and see if you hear audio in the phones. Also check that the Green Led goes on and off with keying and with activation of the switch button.
  1. Connect to an antenna and see if you hear 40 meter cw signals.
  2. If all checks out well, you are ready to install the boards in the housing.