Of course the Pixie final transistor, Q2 S8050, gets darned hot, and I’ve blown one out in the past just holding the key down more than a few seconds. With my Pixie + Red Core Filter, I was seeing about 250 mW out on my QRP meter.
I decided to replace Q2 with an old 2N2219 NPN transistor (one of the few metal can devices I had in my part box). Sure enough, that old device, circa 1975, had better performance than the S8050. My output meter was now about 320 mW out (SA was reading +24.3 mW or 270 mW), and the 2nd harmonic was 50 dB down. A new 4th harmonic showed up, but was also 50 dB down.
Playing around with the output transistor will likely yield some improvements.
When viewed from above, with the board rotated so the BNC connector would be on the right-hand side, Q2 will be flat-side toward the bottom edge of the board, and the pin-out is EBC from left to right, as shown below.
