On Thursday, December 6, 2018 at 2:37:02 PM UTC-5, John Robertson wrote:

For a 3 wire power system (with grounded chassis) that is incorrect as
you suspect.

For a two wire power then it is correct to have the switch on one side
of the line and the fuse on the other as you don't know (unless the plug
is polarized) which side is hot when plugged in.

There is that. I tend to replace line cords with those using polarized plugs, if possible, and then keep the fuse (if any) and switch on the 'hot' line.

General, I would not add a fuse to an AA5, but rather use a purpose-made fused box, plugging the radio into that. In such a way, the fuse level could be varied, and the hot will surely be fused in any case. '

The problem with converting old amps to 3-wires is a matter of hum-loops. Just don't do it. Polarizing the plug is fine. There is a very long explanation of why this is so, but "hum loop" should be enough.

But, at no time with a repaired/restored amp should power exist on the transformer or chassis with the power switch in the "OFF" position. Full Stop.

Peter Wieck
Melrose Park, PA