This machine belongs to panasonic M17 how heart, has a relatively complete cross through the voltage protection circuit, circuit to complex, bring certain difficulty maintenance. In order to make clear its working principle, will the models related to the flow pressure protection circuit sorting out. BEaservice manual download site
 BEaservice manual download site
Protection circuit by Lord Q856, Q857, IC1213 (CPU) and other relevant components and related circuit component. CPU6 feet to protect monitoring signal input, 33 feet for work/standby control output, six feet in normal working conditions for low potential 0 v, 33 feet high output voltage 5 v. Diagram by D819 (TLP621GR) optical coupling, R8161 ~ R818, D820, D821 and relevant components of 300 v rectifier output overvoltage detection circuit; Q852 and relay RL801 makes remote control on/off implement circuit; D832 and it, R831 + B (140 v) overvoltage detection circuit; D852 of + 10 v remote control the power of the overvoltage detection circuit; D451, D452, R458, R454, R462 as field output over current detection circuit; D551 Q553 and peripheral components of output over current detection circuit; D554, R567, D553 high voltage detection circuit. The working principle of the protection circuit is as follows: BEaservice manual download site
 BEaservice manual download site
+ 300 v principle of over voltage protection: when the 300 v rectifier output rise due to other reasons, the pressure drop rises on the sampling resistor R818, after more than D820 reverse breakdown voltage, make its breakdown and rapid reverse conduction, Q803 conducting its output e very high potential via D822, R846 to IC801 4 feet, forced oscillation stop switch power supply, at the same time, the conduction of D821 make D8193, conduction, 4 feet to point B in figure potential down to 0 v, Q857 conduction, C point potential rise, forcing the CPU into standby state protection. BEaservice manual download site
 BEaservice manual download site
+ 140 v over-voltage protection principle: under normal circumstances, a partial pressure values at the R831 about 10 v, D832 cut-off, protection circuit doesn't work. If 140 v abnormally elevated, will make R831 voltage rise, when reach D832 reverse breakdown voltage value rapidly conduction, making A point voltage rise - Q856 saturated conductivity to point B potential drop, prompting Q857 conduction to the C point potential rise, CPU6 foot potential rise and the output of the closing 33 feet. Also Q857c extremely high electricity via R859, D859 to Q856b form self-locking, maintain Q856, Q857 saturated conductivity (point B low potential), make Q852 blackouts, relay RL801 release protect host power into the state.

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