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An AC power delay circuit
For the PL-177 amp, I needed a circuit to delay the application of B+ power until the tubes have warmed up.
Since I used a switching power supply for heaters and a separate HV supply, I wanted to switch the AC power to the two systems, as opposed to messing with the high voltage B+. So I designed this:
(Download it in PDF)
It is similar to the muting relay delay circuit I built earlier, but it has larger power relays that can switch up to 10A at line voltage. It also integrates a small "housekeeping" power supply, to run the timer and power relays. It also integrates inrush limiters and MOVs. Sorry, I don't have a parts list (BOM) completed, but it is pretty obvious from the schematic. The power transformer is a Triad FP12-200, and the power relays are Omron G6B-2214P-6VDC.
I will make these PCBs available in my eBay store.