(03-06-2019, 10:53 AM)ppppenguin Wrote: As far as I can see they drive solenoids for the pinch roller and brake. PM802, PM801 on the diagram. They might be part of a circuit that gives a higher voltage to a solenoid to get it going which then reduces when it has pulled in.
The AC supply to the brake and pinch roller solenoids supply rectifier is via S801, 100v to actuate and 60v to hold, it switches to 60v hold once the brake solenoid plunger is more or less home.
With the tape threaded up as normal, the collector and emitter of Q705 are shorted out due to S802, so at that stage Q705 doesn't supply or drive anything per se.
So far as I can make out, Q705 is in circuit the instant that the pole of S802 breaks from the NO contact, at that point Q705 is in series with the supply and take up reel motors in their 0v side, as soon as S802 makes NC the reservoir capacitor for the brake and pinch wheel solenoid supply is connected across the auto shut off solenoid enabling that solenoids actuation.
Lawrence.
