Footwarmer aka Widowmaker Transformerless linear amplifier. Yep, I put the gloves back on again.

DIsclaimer: This video is for research, scientific, technical, experimental, entertainment, and educational purposes only. On the bench is a Footwarmer transformerless linear amplifier. This one takes all voltages straight of the mains. HV, Screen, Bias, LV and filament are all taken off the mains. It has a HV power supply board with a quitupeler for the HV, with the screen taken at the voltage doubler point of the quintepeler, and also the negative bias is derived off the HV PCB. The low voltage and filament is derived off the main board. It takes the 120 line voltage thru the 2 30kd6 30 filament volt tubes in series, then to a regulator that turnd the 60v that is left to dc and then regulates it down to 12v to run the keying circuit and preamp. This is a tetrode (turbocharged) amp with full screen and bias voltage. It is grid driven with a tuned input circuit. Even though the input circuit is tuned, it is fixed (not adjustable). With 4 watts in with very little swing, on low, I was getting 2 watts dead key but swinging to 45 peak. On high, it was dead keying about 30 and swinging to 90 peak. It would do a little more if I pushed it with a radio that was doing more. If I wasn't afraid of making my wife a widow, I would really like this amp. However, I am not the one trying to let this amp live up to its nickname. I grounded this amp well, ran it thru an isolation transformer and a variac. I also put on the gloves and kept them on for this one. I like that it is light weight, and because of the transformerless design, it has very low HV drop. I also like modulator type amps like this a lot. However, those transformerless designs scare me. Off to the shelf it goes.