Halifaxhops is right on the money here, both transistors used… rather they being PNP or a NPN served only as a switching device, switch on switch off. The older “can” type transistor has a cooling paste inside and does require to be bolted dissipate heat. The newer silicone transistor has NO paste and requires a much needed heat sink to be bolted right to the tang of the transistor.
If they just bolted the transistor to the metal case instead of faking it, it would have worked just fine.
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