Hey guys, I noticed on Alex's EHHA page, he mentions that it's a good idea to have 2 power switches, one for the heater supply to warm up the tubes for about a minute before turning on the main supply, so there isnt any funny business going on with the tubes as they warm up.
I said to myself, hey that sounds like a perfect place for a little delay circuit that would be controlled by the heater supply.. Turn on the 12 v supply. the delay counts down for a minute, then trips a relay to turn on the main supply..
And since the internet is all about not re-inventing the wheel here's a circuit to do it:LM555 Timer Circuits
I particularly like the one called: Delay circuit with flashing indicator LED.
Even the basic delay circuit would be useful..
It would be pretty simple to breadboard, and the main expense would probably be a relay with heavy enough contacts for the main power suppy..