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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.

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