I am going to try plastic transistors for the bias circuit.
Nick (THD+N) told me this.
“ Q118 can be replaced by a plastic T0-126 transistor such as 2SC3421. Notice that the 2SC3421 is an all plastic case transistor and you can mount the 2SC3421 directly to the heat sink with thermal grease. If youuse another type of TO-126 type transistor for a bias transistor, ensure it is all plastic. If not, then you may have to use an insulator and thermal grease to ensure electrical isolation. A lot of transistors can be used for the 2N3403 bias transistor substitute. Cut the leads from the 2N3403 and solder them to the new T0-126 type transistor leads. Make sure you identify the correct pin-out of the new transistor and attach the bias wires from the 2N3403 in the correct manner. Bias will need to be readjusted when using a different type transistor. I am using 2SC3421’s now in a 700II and they work great. No issues”