The TIP31/32 have metal backplates that are electrically connected to the collector.
The heatsink would normally be earthed to prevent hum and other pickup, and for safety.
So they need to be mounted in an isolated manner from the heatsink.
They are designed for a single screw fixing and this needs an isolating bush/washer to pass through when the assembly is screwed to the heatsink.
Also the metal pad on the transistor needs an isolating shim/washer to prevent contact between the transistor and the heatsink.
See what you can dig up, on the net then come back and ask questions. I think there should be a section in the Ebook about this.
The heatsink would normally be earthed to prevent hum and other pickup, and for safety.
So they need to be mounted in an isolated manner from the heatsink.
They are designed for a single screw fixing and this needs an isolating bush/washer to pass through when the assembly is screwed to the heatsink.
Also the metal pad on the transistor needs an isolating shim/washer to prevent contact between the transistor and the heatsink.
See what you can dig up, on the net then come back and ask questions. I think there should be a section in the Ebook about this.