Figure 17 Almost complete schematic of Heathkit IP-17 bench power supply. Metering circuits have been omitted. This supply has 2 transformers. T1 is a plate transformer which has three secondary windings. One is a 175 volt winding for the screen grids of the pass tubes, the second is a 210 volt winding for the plates of the pass tubes, and the third is a 600 volt center tapped winding for the reference supply. T2 is a filament transformer with 4 windings. Three of them are 6.3 volt windings and the fourth is a 12.6 volt center tapped winding. The line plug has its ground, round, prong connected to chassis. The neutral prong connects to the bottom ends of the primaries of both transformers. The hot prong of the plug connects through a 3 amp fuse then the on off switch then to the top end of the primary of T2. The connection at the top end of the primary of T2 connects through the standby switch to the top of the primary of T1. Note. All semiconductor diodes in the original product were made up of two diodes connected in series. If designed at the present time, diodes with higher voltage would be available and only one diode would be used. Therefore, the diodes will only be described as a single diode. End of note. The top end of the 210 volt secondary of T1 connects to the anode of a diode. The cathode end connects to the positive end of a 68 u f 450 volt electrolytic capacitor. The junction of the diode cathode and capacitor will be called plus 600 volts. The negative end connects to the bottom of the secondary. The top of the secondary also connects to the cathode of another diode. The anode connects to the negative end of another 68 u f 450 volt capacitor. The junction of the diode anode and capacitor will be known as common. The positive end connects to the bottom end of the secondary. The output jack of the power supply which is labeled B minus, C plus is connected to common. the plates of the pass tubes, two 6L6GBs, connect to the plus 600 volt point. The top end of the 175 volt secondary connects to the anode of a diode. The cathode of this diode connects to the positive end of a 22 u f 350 volt capacitor. The junction of the diode and capacitor connects to one end of a 1 k ohm 1 watt resistor. The other end of this resistor connects to the positive end of another 22 u f 350 volt capacitor. The junction of the resistor and second capacitor connects to the ends of two 100 ohm resistors. The other end of one of these resistors connects to the screen grid of one of the 6L6GBs. The other end of the other 100 ohm resistor connects to the screen grid of the other 6L6GB. The bottom end of the 175 volt secondary connects to the negative ends of both 22 u f capacitors and also to the cathodes of both 6L6GBs. The two cathodes also connect to the output jack which is labeled B plus. A suppressor grid or beam forming element, whichever you prefer, is connected inside each of the two 6L6GBs to its cathode. We will leave the pass tubes for now. The control grid connections to these tubes will be described later. Each end of the 600 volt center tapped winding connects to a plate of a full wave rectifier tube labeled as V4, 6X4. The cathode of V4 also connects to the positive end of a 22 u f 450 volt capacitor. The cathode also connects to the positive end of a 47 u f 450 volt capacitor. The cathode also connects to the anode of a gas voltage regulator tube zero eh two V2. The cathode of the 6X4, V4, also connects to the point known as common. The center tap of the 600 volt winding connects to the negative end of the 22 u f 450 volt capacitor. A 1.5 k ohm 2 watt resistor connects from the negative end of the 22 u f cap to the negative end of the 47 u f cap. Another 1.5 k ohm 2 watt resistor connects from the negative end of the 47 u f cap to the cathode of V1, the other zero eh 2. This point will be referred to as the minus 300 volt point. The anode of V1 connects to the cathode of V2. This point will be referred to as the minus 150 volt point. The two VR tubes constitute the reference supply. We will come back to it in a moment. But first…One of the 6.3 volt windings on T2 is connected to the heater of V4 the 6X4. One side of the heater is connected to the cathode. Another of the 6.3 volt windings on T2 is connected to power the heater of V3, 6BH6, error amplifier tube, not previously mentioned. One side of V3s heater is connected to its cathode. The third 6.3 volt winding is connected to the heaters of V5 and V6 in parallel. These are the 6L6GBs. One side of the heater circuit is connected to the cathodes of V5 and V6. Now back to the reference supply. A 50 k ohm pot is wired with its top connected to the common point and its bottom to the minus 150 volt point. This is the front panel control which is labeled C minus volts. The wiper of this pot connects through a 22 k ohm resistor to the output jack labeled C minus. There is a 0.05 u f capacitor connected between the C minus output jack and common. There is a 33 k ohm 1 watt resistor connected between the minus 150 volt and minus 300 volt points. The cathode of V3, 6BH6 connects to the minus 150 volt point. The screen grid of V3 connects to a 150 k ohm resistor and the other end connects to the cathode of V3. The screen grid also connects to a 0.22 u f capacitor, the other end connects to the common point. The screen grid also connects to a 1 meg ohm resistor, the other end connects to the plus 600 volt point. The suppressor grid of V3 connects to its cathode. The plate of V3 connects through a 470 k ohm resistor to the B plus output jack. The plate of V3 also connects to one end of two 1 k ohm resistors. The other ends of these two resistors connect, one to each control grid of the two 6L6GBs. The control grid of V3 connects through a 1 k ohm resistor then to the wiper of a 500 k ohm pot which is labeled B plus set. The control grid of V3 also connects through a 0.056 u f capacitor to the B plus output jack. The top of the B plus set pot goes through a 680 k ohm resistor then through a 500 k ohm pot connected as a rheostat to the B plus output jack. The pot is labeled zero adjust. The bottom of the B plus set pot goes through a 240 k ohm resistor then a 200 k ohm pot connected as a rheostat to the minus 300 volt point. This pot is labeled 400 volt adjust. The heater voltage output jacks are connected as follows. Picture three jacks in a vertical line. Between the bottom and middle one is a label indicating that the voltage between them is 6.3 volts. Between the middle and top jacks is a label indicating that the voltage between them is 12.6 volts. The center tap of the 12.6 volt winding on T2 connects to the bottom jack. The bottom end of this winding connects to the middle jack. The top end of this winding connects to the top jack. This completes the verbal description.
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