h. Also 230vac is applied across the rotor-phase-shift capacitor and exits at the
closed contacts of H8/08 of Re-4 to the X-ray tube. 230vac from the GT1 triac turns on
an optocoupler OC1, allowing 24vdc to trigger SCR1. Silicon-controlled rectifier 1
conducts, passing 24vdc to the emitter of the transistor Q1, the switch is inhibited
until the boost cycle ends.
i. When the 0.1-μFd timing capacitor reaches its preset charge point (set by
P1), SCR2 is triggered putting a low on the base of Q2 transistor, turning Q2 off and
turning Q1 on. Relay Re-2-RC de-energizes and its contacts return to their normal
position with the short circuit removed from the three sensors. When 115vac on lead H3 is
switched from the GT1 to the G2 triac.
j. With the GT2 triac turned on, 60vac from lead 601 is reduced to 50vac via the
10-ohm 100-watt slider motor-run-adjust resistor to lead H1F, through the GT2 triac and
the three sensing circuits, and across the rotor phase shift capacitor to exit at H7/07 and
H8/08 of Re-4 to the X-ray tube. The 50vac now maintains the correct anode speed of
k. The three sensing circuits are: in-phase current sensor, shifted-phase current
sensor and capacitor-voltage sensor. These sensors are in series and control the
24vdc to the "GO-NO-GO" relay Re-3 via the 2N5308 transistor. The sensitivity of the
three sensors is adjusted by potentiometers P2, P3, and P4. The sensors ensure
adequate voltage and current is available to the stator windings of the X-ray tube for
proper anode speed before an exposure is permitted. These sensors protect the X-ray
tube from being damaged by exposures on a stationary target. When any sensor is
inoperative, no exposure is possible due to lack of a rotor-to-speed signal.
l. When transistor Q1 turns on, 24vdc goes to the coil of the "GO-NO-GO" relay
Re-3 but it cannot enable until the 2N5308 transistor goes into conduction. The 24vdc
goes to the sensors and, if all sensors are operating, turns on the 2N5308 transistor
which enables the "GO-NO-GO" relay closing contacts H3/OHO and H5/H6 going to the
exposure circuit on lead OHO, and to the back-up timer on lead H6.
m. This gives the two circuits the necessary rotor-to-speed signal for exposure.
Also, the "GO" LED is illuminated. When the PREPARE push button is released, lead
H3 goes low turning off the GT2 triac, the 24vdc source drops to zero, the "GO" relay
inhibits, and the rotor coasts to a stop.
n. In the fluoro mode, the rotor control operates in the same manner with one
exception. The tube-select relay is enabled connecting H7/U7 and H8/U8 for the