Mode switch puls mod
Yaesu FT-221R mode switch puls mod
When I used the rig for the first few times I noticed that when switching from CW to USB or AM, the rig switch to full output. This could be fixed with switching off the rig between switching modes but that's not the correct way.
On the Internet I found this quote :" Probably many preamps died since the rig gives,shortly, full output when switched from CW to USB or AM. Removing a connection between audio and CW tone oscillator is all you have to do. This connection is not on the schematic diagram and is obviously a wiring error. Remove bottom cover and locate pin 8 on the audio board. Now you see a white/green and a yellow wire,remove the yellow one. Remove it completely or isolate. success! Nanko PA0V "
I verified the wiring and the yellow wire was there. Looking through the schematics I confirmed the wire was meant to be and as PA0OV described I removed the wire. Working fine now between switching modes.