It’s always a little daunting but it’s also the part I like best – doing the smoke tests. Testing the power supply was really all about ensuring that the SMT caps had been soldered in correctly and that there were no solder bridges.
First I tested current draw with a 1K resister added to the positive probe of my DMM to restrict the current in case of a bridge. I applied 12V power and took readings.
3.0mA so all was in order.
Next I checked the power at the 12V, 5V and 3.3V rails: all fine there.
Now it was time to build the local oscillator.
Once more I needed to check current draw but this time I did this with a 100 Ohm resister instead of a 1K Ohm one. The readings I obtained were excellent. I was now safe to test without the protection of the resister and again got great readings, all of which were under 80mA.
Next up was a frequency test. I set the dip switch on the PCB to 7.046 MHz and applied 12V. I then tuned my FT-817 to 28.184 MHz (four times the local oscillator frequency of 7.046 MHz) and set the rig to CW mode. After attaching a length of coax in the 817’s antenna socket and draped it close to the Softrock, I heard a good, solid tone.
Excellent. Another smoke test passed.