Power circuit of LBO-522 dual trace oscilloscope

Power circuit of LBO-522 dual trace oscilloscope

Shown is the power supply circuit of the LB0-522 dual trace oscilloscope . Its basic function is to provide power with different voltage values ​​for various circuits and devices of the oscilloscope. Using the transformer step-down method, the 220 V AC voltage is reduced by the transformer into 5 groups of low voltages. One group provides a filament voltage of 6.3 V for the oscilloscope tube , and the remaining four groups are rectified and filtered by their own bridge rectifier circuits. And the voltage is stabilized by the voltage stabilizing circuit , and then the voltages such as dl+s V, ±12 V, +150 V, +270 V are sent to each circuit board of the oscilloscope respectively.     1. The 270 V power supply supplied by the +270 V voltage stabilizing circuit     scanning circuit is rectified by a bridge rectifier stack and then filtered and output by an RC filter, and then sent to other circuit boards of the oscilloscope. The voltage value during normal operation can be measured by the TP1 detection point. If the +270 V power supply is abnormal, it will cause the oscilloscope scanning circuit to be abnormal. If the voltage is low, check whether the filter capacitor C2 has leakage or deterioration.     2. +150V voltage stabilizing circuit The     +150 V power supply is rectified by the bridge rectifier stack (VD2) and then output through the regulating tube VT1, and the sampled voltage is sent to the ⑤ pin of IC1.     3. ±12V power supply voltage stabilizing circuit     ±12V power supply is rectified by bridge rectifier stack VD4, the adjustment tube is VT5, and the error amplifier is ICI (IC1 has two amplifiers, one is used in the +150V power supply).     4． The +12V and +5v voltage stabilizing circuits     also have a +12 V power supply and a +5 V power supply which are regulated by three-terminal voltage regulators IC2 (7812) and IC3 (7805) respectively, and the rectifier circuit shares VD5.