This is a variable voltage analog power supply based on the LM317 adjustable voltage regulator. The LM317 includes on-chip current limiting, thermal overload protection, and safe operating area protection. All overload protection remains fully functional, even if the ADJUST terminal is disconnected.
The LM317 can output up to 2.2 amps, provided the difference between the input and output voltage is less than or equal to 15 VDC. The output current drops dramatically to 0.4 amps if the input-output difference is equal to 40 VDC. These values give an indication of the “safe operating area” protection.
The voltage is adjustable from 1.2 VDC to 30 VDC via a “VOLTS ADJ” potentiometer. There is also a “MAX ADJ” trim potentiometer that can be used to limit the maximum output voltage. The input is protected by a 1.8 Amp auto-reset fuse. Input voltage can be either 6-24 VAC or 8-35 VDC.
AC inputs are rectified by four 1N5402 (3 amp) diodes in a full bridge configuration and filtered by two 2200uF electrolytic capacitors. The main output regulator (TO-3 package) is fan cooled allowing continuous operation at high current levels and high ambient conditions. The regulator has built-in thermal protection and current limiting. The maximum output voltage is 30 VDC (with an input of 24 VAC or 35 VDC).
The two 6 inch diameter component mounting disks are made of 1/8 inch Delrin and the four 5/8 inch diameter support spacers are also made of Delrin.
The power transformer is a Triad F8-24 with a output of 24VAC at 4 Amps. A 1 amp fuse is installed on the transformer primary.