Schematic. Part 1, the power supply. The wide (neutral) prong of the line plug goes to the bottom end of the primary of T1 the 24 volt power transformer. The narrow (hot) prong of the plug goes to one terminal of the on/off switch, an S P S T. The other terminal of the switch goes to one terminal of a fuse which is labeled 2 amps and the other end of the fuse goes to another fuse which is labeled 1/2 amp. The other end of the 1/2 amp fuse goes to the top end of the primary of T1. The center tap of the transformer secondary goes to common and chassis ground. The two ends of the secondary go to the AC terminals of a standard bridge rectifier. The positive output of the bridge goes to the positive end of a 100 microfarad electrolytic capacitor. This point is labeled V plus. The negative end of this capacitor goes to ground. The negative output of the bridge goes to the negative end of another 100 microfarad capacitor and this point is labeled V minus. The positive end of the capacitor goes to ground. The V plus point goes to the input terminal of a 78L12 voltage regulator I C. The ground terminal goes to ground and the output goes to a point labeled plus 12 V. The V minus point goes to the input terminal of a 79L12 regulator I C. It's ground terminal goes to ground and its output terminal goes to a point labeled minus 12 V. There are 0.1 microfarad caps connected from the input terminal of each I C to ground and from the outputs of each I C to ground, 4 in all. The plus 12 v point connects to the positive end of a 25 microfarad cap and the other end is grounded. The minus 12 v point connects to the negative end of a 25 microfarad cap and the other end is grounded. Part 2, Excitation voltage source. We begin this section with a 5 position 3 deck switch. The five positions are 1; 0 to 40 v, 2; 0 to 20 v, 3; 0 to 10 v, 4; 0 to 5 v, and 5; 0 to 2.5 v. These will be shortened by calling out the upper voltage only. On deck A both the 40 and 20 v positions go to the junction of the two fuses which is the hot side of the AC line. On deck B the 40 and 20 v positions go to the wide prong of the power plug, the neutral side of the line. The rotor on deck A goes to the top of the Variac. The rotor on deck B goes to the bottom of the Variac and the bottom of the primary of T2 which is the excitation transformer. The top of the T2 primary goes to the wiper of the Variac. The secondary of T2 is 40 volts center tapped. The bottom of the secondary goes to a banana jack labeled DC plus. This is where the DC power supply is connected. The center tap and top of the secondary connect to deck C of the excitation range switch as follows. Top to the 40 and 10 v positions. Center tap to the 20, 5, and 2.5 v positions. The rotor of deck C goes to the upper jack of the choke under test pair of jacks. Now back to decks A and B. The 10, 5, and 2.5 volt positions of deck B, that's the one who's rotor connects to the bottom of the Variac, all connect to one end of the secondary of T1, the 24 v transformer that also provides DC power to the op amps. On deck A the 10 and 5 v positions connect to the other end of the T1 secondary. The 2.5 volt position connects to the center tap of T1. Part 3 the AC only voltmeters. Although the simplified circuit above shows two AC voltmeters there is actually only one in the instrument. The voltage across the current sampling resistor is amplified through an op amp and fed to one position on the inductance range switch. The lower jack of the choke under test pair goes to one end of the 1.0 ohm resistor. This point is also grounded but a wire should go directly from the jack to the resistor. The other end of the 1.0 ohm resistor goes to a jack labeled DC minus. A wire connects to the resistor terminal at the grounded end of the 1.0 ohm resistor and goes to one end of a parallel combination of a 1 meg ohm resistor and a 0.47 microfarad cap. The other end of the paralleled R and C goes to pin 5 (noninverting input) of a T L O 72 op amp. Connected to the other terminal of the 1.0 ohm resistor is the negative side of a 4.7 microfarad cap. The positive end goes to one end of a 5 k ohm trimming pot, labeled gain set, connected as a rheostat. The other end of the pot goes to a 9.1 k ohm resistor and the other end goes to pin 6 (inverting input) of the op amp. A 1 meg ohm resistor and a 10 p f cap in parallel connect from pin 6 to pin 7 (output) of the op amp. The meter range switch is a 6 position 1 deck switch. Its positions are 0.5, 1.5, 5, 15, 50, and Set. The set position goes to pin 7 of the op amp. The rest of the range switch is wired as follows. a 1.6 meg ohm resistor connects between the 0.5 and 1.5 positions. A 560 k ohm resistor connects between the 1.5 and 5 positions. A 160 k ohm from 5 to 15, a 56 k ohm from 15 to 50, and a 24 k ohm from 50 to ground. The 0.5 position of the range switch connects through a 0.1 microfarad cap to the top jack of the choke under test jacks. The rotor of the range switch connects to pin 3, the noninverting input of the other op amp unit in the dual op amp T L O 72 I C. Pin 8 of the I C goes to plus 12 v and pin 4 goes to minus 12 v. The output, pin 1 of the op amp goes to the cathode and anode at one corner of a bridge rectifier. An analog DC panel meter connects from the two cathode corner to the two anode corner with the positive side of the meter to the two cathodes. The as yet unassigned corner of the bridge goes to the top of a 1 k ohm trimming pot, labeled meter cal, connected as a rheostat. The bottom is grounded. The junction of the bridge and pot connects through a 47 p f cap to pin 1, output, of the op amp. The same junction connects to the parallel combination of a 110 k ohm resistor and a 0.1 microfarad cap. The other end of this R C combo goes to pin 2, inverting input, of the op amp. End of verbal description.