This stage has a fairly high component count, so patience was the order of the day. I decided to take it nice and slowly so as to enjoy the process. It would also make sure I didn’t make any mistakes.
The stage consists of four unitary gain op-amps, arranged in pairs. The left channel’s input resolves to two signals: 0° and 180°. The right channel’s input resolves to two signals: 90° and 270°.
Each of the 14 resisters was checked with my DMM to ensure I had the correct ones for insertion into the PCB; it’s easy to mistake brown for red in the colour coding on the tiny resisters.
The Op Amps themselves (IC SOIC-8 dual Op-Amps) were also tiny beasts each with eight pins that required careful soldering so as to ensure no solder bridges or spashover on any of the adjacent empty holes. For this task I used a very handy suction tool that Wallace, VK4CBW, gave me some time ago.
Once all the components had been soldered into place and I was certain there were no cold solder joints or solder bridges, it was time to conduct the usual current and voltage tests according to the instructions.
Thankfully my patience paid off with all reading being as expected.
Next is to tackle the TX mixer.