I used a series vacuum tube regulator in my power supply to provide a variable constant-voltage output, and the negative feedback probably went a long way toward suppressing ripple in the output.īe careful with your power supply. Depending on the load current and maximum ripple you desire, you may want additional capacitance. The 47 μF, 800 WVDC, capacitors (very hard to come by with that voltage rating!) will make a fine pi filter with a 10 Hy choke for a 600 VDC power supply. I presume you realize this type of power supply is virtually obsolete, but it sounds like a good nostalgia project. Wouldn't recommend trying this "experiment" with solid-state rectifiers. I got away with that because vacuum tube rectifiers are inherently current-limited. I was somewhat amazed that I was able to draw a fat, hissing, spark between the choke and chassis ground. This was my first introduction to large inductors used as power supply filters. I don't remember what my choke resistance was, but it did not cause any appreciable voltage drop when I loaded up the transmitter, nor did I ever get any signal reports complaining of "hum" on my transmitter carrier.Īs mentioned, early loudspeakers used a field coil instead of a permanent magnet and this coil was usually part of a pi-network filter for the power supply. The process is known as rectification, since it 'straightens' the direction of current. The reverse operation (converting DC to AC) is performed by an inverter. It is important that the DC resistance of the choke be substantially less than the reactance for good filter efficiency. A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction. A 10 Hy choke has a reactance of 2 (pi) (120) (10) ohms or slightly more than 7500 ohms at the ripple frequency. The ripple frequency of a full-wave rectifier connected to the 60 Hz mains is 120 Hz. This was the power supply for my 75 W homebrew Novice CW transmitter based on the venerable RCA 6146B beam power-pentode vacuum tube.įor amateur radio purposes, brute force was the name of the game. I think it was about 10 Hy and good for at least 1 A. It has been many years, circa 1966, since I constructed a plate power supply using a 5R4-GY vacuum tube rectifier, high-value electrolytic capacitors, and the biggest choke I could get my hands on.
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