When you turn on TPH positive half-wave supply 220 volt voltage passes through the circuit VD2R3R4 and charges the capacitor C2. As soon as the voltage U exceeds thyristor turn-VS2, and will miss the last part of the positive half the load. VD4R5 circuit protects VS2 current management.
Changing the total resistance R4, can be adjustable from 40 to 220 V output voltage for direct measurement of which is indicating voltmeter PV1. Indicator lamp HL1 serves to monitor the mains voltage and the integrity of fuses FU1 and FU2.
Both capacitor TRN cheap and common -type of MBM. For R1, R2 and R5 can be applied MLT-0, 25. On-site work is well R3 MLT-0, 5 MLT-1. As a variable resistance suitable JS1. Voltmeter -TS4201 or similar type for 250 V AC. Shown on the wiring diagram diodes can be replaced by less powerful, for example, or KD102B KD105B. Thyristors -with a reverse voltage of 300 V, for example, or KU202N KU202L. And if you intend to use TRN load not exceeding 350 W, we can apply and KU201L.
Neon lamp HL1 of TN-0, 2.