Based on work of Bob, W9RAN and some modest contribution from my side, here is the block diagram of the popular Xiegu G90 transceiver.
And, based on reverse engineering of parts I am interested in, here is the schematic. Attention, it is work in progress!
Last version: September 15, 2021 - minor corrections
I've been following your adventures exploring the inner workings of the G90. I've downloaded all the schematic diagrams that you've put together about the radio.
Recently I blew up the two 100 Ohm resistors in the area around the key jack. I sent Radioddity a note and they responded with a schematic of that area. The drawing is included with this email to add to your collection.
The problem came from testing a EFHW antenna with the 49:1 balun sitting a meter from the radio and connected by what turned out to be a faulty cable. The radio wasn't grounded and the key line did not have any RF suppression/chokes on it. I figure the RF got past the RFC and the zener diodes shorted the RF through the 100 Ohm resistors to ground.
I repaired this with parts I had and added 1nf caps on the high/key jack side of the RFCs. We'll see how that works out. Oh, and I grounded the radio and put a clip-on ferrite on the key line.
Stay safe and well, Adrian. We will survive!