I will only tell you this once!!! CAUTION CAUTION CAUTION!!!!
These are STV3 diodes. They are very very difficult to obtain these days as they have not been manufactured for a good many years.
You must unscrew those, and whatever you do, do NOT grab them and move them around the place, be very very careful, hold them by the legs near the circuit board to move them out of the way, do not bend them by holding the diode, they will break off.
If you are unlucky enough to have one that is broken and have not noticed, the amplifier will destroy itself, blown output transistors, burned out emitter resistors....you do not want to go there!!
Extreme caution required!!