(03-06-2019, 09:40 PM)Refugee Wrote: During an unexpected power down the solenoids clearly are disengaged rapidly.
Without an extensive study of the mechanical parts in the manual I would guess that the solenoids either release the brakes or engage the motors when they are powered.
The transistor turns them off rapidly when power is lost via there negative supply. The switches select positive supplies to them as required for normal operation.
Yes, the transistor Q705 is in circuit between the -ve of the reservoir capacitor C801 and the bottom end of the solenoid but only when the common and NC contacts of the auto shut off switch S802 are open. The way I see it, that would lengthen the time before the brakes are applied due to the charge on C705, not shorten the time, for the shortest time Q705 wouldn't be needed because without it C801 is disconnected from the solenoid the instant that the common and NC contacts of S802 are open.
What's going on with Q705 etc?
Lawrence.
