I used a bridge rectifier salvaged from an old PC power supply. This will allow the filter caps to be recharged twice every cycle of 60Hz powerline, instead of just once. And tube heaters have less hum leakage when they are at a positive voltage compared to the cathodes, like 50V. And this bridge circuit will make the middle of the heater string look to have such a positive voltage, so I rewired the string so the first audio driver tube sees the least AC ripple and a fairly constant voltage as seen by the heater and cathode voltage difference. But the chassis is hot no matter which way the radio's power plug is connected to the powerline. But this is for advanced hobbyists.
In any event, one can acquire a far amount of usable parts from salvaging tossed computer monitors, power supplies and such. This is an old tradition in ham radio, known as the "junk box". Such junk will likely have usable rectifier diodes.
08-04-2009, 10:59 PM
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