Thanks very much for your quick and thorough response. You've helped me immeasurably, especially by introducing the concept of the "hybrid tube/SS" rectification scheme.
EWBrown wrote:That circuit, as it is shown, would not work, as there is no "return" for the negative portion of the AC voltage.
Yup, I realized that right after I sent my post. No return, no current flow.
EWBrown wrote:IMO the preferred method, is to start out with your circuit, and then add two SS rectifier diodes to each secondary, anodes connected together and to ground (zero volts) bus, and connect one SS diode's cathode to each of the rectifier tube plates (pins 4 and 6).
IMHO, your suggestion is spot-on because it resolves so many real and perceived issues all in one swoop: inrush limitation, cathode stripping, no need for a complicated "soft-start" circuit, and maintains an elegant simplicity.
I've spent dozens of hours researching the SS rectification B+ issue in tube amps but have never come across this solution before. Just yesterday, before you suggested the hybrid bridge, I concluded that the guitar amp builders might have the right idea: a simple standby switch that cuts B+, although I had some reservations about the safety of running a metal toggle switch 500% above it's voltage rating.
Alternatively, I was just starting to look into the Amperite delay tubes.
I'm at work now (kind of), but I'll revise the circuit later today to illustrate your concept and post it in a follow-up message. I'd appreciate your quick "once-over" to make sure it's what you intended.
EWBrown wrote:It is conceivably possible to simply add a second 5VAC winding, with properly insulated wire, wound around the outside of the toroid's existing windings.
Another good idea. Sounds like I get to experiment this weekend and see what the VTVM tells us. If it looks promising, I'll buy some enameled wire and give it a go.
Thanks very much for sharing your expertise with us.
Regards,
Chris