Hello List et al I frequently come across a piano heater - really ancient - which is simply an insulated element which has been attached in a zig-zag configuration to the back of the "knee-board" There is a round three pin socket (male) let into the panel. I have never come across one working though. The length of that element is such that the configuration takes up at least ten side-to-side (or end-to-end) stretches across the back of the knee-board. This is the sort of heater which could cause fires.... Regards Michael G (UK)
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