Things to get my v4 board behaving better-er..
Firstly, thanks for everyone who has gone and dug into this stuff before me. I'm actually glad the radio is working now. Yeah, input and output filtering is next!
Here's some stuff I found I had to do to the v4 board to get it to behave better-er.
* it's now putting out CW between 5 and 10w on all bands - i had to adjust RV1 /and/ do a proper BFO/VFO alignment to get it to behave well.
* the mic gain using the stock mic was way, way too low - sub-1W peak output on my scope/analyser. I changed the two resistors mentioned at https://ubitx.net/mod-tx-compression/ to modify the behaviour of the mic amplifier. It now approaches the power limit I see with the CW output.
* the speaker amplifier bias needed changing - I replaced the two bias diodes with a pair of 1n4148 with a drop of around 700mV; the amplifier no longer distorts!
* the CW tone generation is way way too loud to use with the speaker turned up - I added a 50k trimpot between R253 and VOL-H. I may actually go do what Kenwood does with side-tone and feed it into VOL-M so the volume level of the CW side tone is independent of the volume knob.