(2)
Functions of the driver.
(a) The collector of the power driver Q3 is in phase with the collector of
the transistor (pin 7) on mv A2.
(b)
Q2, Q3, and Q5 initiate the on and off drive to the power output stage
Q4.
(3)
Functions of the output.
(a) When Q3 is turned off by the drive from mv A2 - pin 1, the magnetic
energy stored in T2 (winding pins 1 and 14) is induced into T2 (winding pins 4 and 11)
switching the output transistor Q4 to on.
(b) The current through Q4 now stores the magnetic energy in T3
(winding pins 1 and 2). With Q4 on, the current increases with time. When Q4 is turned
off, T3 (winding pins 1 and 2) resonates with C13.
(c) The result is a damped sinusoid wave shape. The energy is coupled
by secondary windings to generate output power. The wave shape damping varies with
the particular output load. With average physiological loads, one or two high amplitude
cycles exist.
(4)
Functions of the power supply.
(a) The power supply is an unregulated +50 volts and regulated 5, 10,
and 15v by zener diodes.
(b)
The secondary rectification is by a full wave bridge.
Functions of the switch.
(5)
(a)
The output power can be switched on and off by the foot switch or
hand switch.
(b) Closing E21 to ground turns off Q2 and Q5, and increases light
emitting diode (led) current to optically excite the silicon detector chip to drive the gate of
triac Q1. With Q2 off, A2 functions as a multivibrator.
(6) How to generate sound. Audio is generated by pulsing the solenoid
(buzzer) on and off from the ac secondary voltage.
c. Access the Unit. You can access the entire printed circuit board (pcb) and
operative assembly by removing the back screws, 4 pcb screws, and the control knob.
Refer to figure 2-2.
MD0363
2-5
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