On 6/11/24 17:42, Don R via Jukebox-list wrote:
To add to this, Don Leslie’s organ loudspeakers with a pair of 6550s and a 5U4G were updated too 8 silicon diodes and a dropping resistor to prevent popping of the diodes from the near dead short of the filter capacitors upon initial power up.
A choke-input power supply filter is much more friendly to solid-state rectifiers. NTC thermistor is an alternate choice to the resistors that greatly reduces inrush but doesn't generate as much heat or waste as much power during operation.
Of course both of these are more expensive than the alternatives.
Granted these were instrument amplifiers and not hi-fi quality but they operated for decades trouble free.
Number of on-off cycles as opposed to total time in operation would correlate better with failure rate IMHO.