Quantum QT-740, Руководство по обслуживанию

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Chapter 3 Theory of Operation
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Models QT-740 & QT-750 - Service Manual
through A1J2-4 and/or A1J2-5, respectively, to buffer/level shifters
A1U3E and A1U3G. The high outputs from A1U3E and A1U3G de-ener-
gize DOWN relay A1K3 through components A1U4D, A1U1B, and A1U4C
and INHIBIT relay A1K4 through A1U4D and A1U1C. The motor drive cir-
cuit is interrupted, thereby stopping tabletop vertical motion.
• A sensor is located on the Drive and Sync belts to detect the presence of
each belt. Normally, Drive Belt Sensor Switch S22 and Sync Belt Sensor
Switch S23 are closed applying a low (ground) through A1J2-19 to tran-
sistor A1Q4. The low signal turns off A1Q4, causing the input at A1U5B-5
to be high. The resulting low output at A1U5B-7 enables the motor drive
circuit for operation as described previously. In the event a belt breaks,
S22 and/or S23 open removing the ground at A1J2-19. Transistor A1Q4
turns on applying a low input to A1U5B-5, which outputs a high signal at
A1U5B-7. The motor drive circuit is interrupted, thereby disabling DC
motor operation.
• An temperature monitoring sensor mounted on the DC Motor monitors its
temperature. If the temperature exceeds 70°C, the switch opens and
disables the DC Motor operation in the same manner as the drive belt
sensors, described in the previous paragraph.
Float Control
Model QT-750 tables have two FLOAT foot pedals, which operate switches S11
and S12 and a FLOAT push button switch (S13) located on the right Transverse
Assembly cover, just below the tabletop. When S11, S12, or S13 is activated, a
high FLOAT signal is applied through 6-Way Table Control Board connector A1J2-
18 to one-shot A1U6B. One-shot A1U6B produces a 47 second pulse that turns
on FET's A1Q1 and A1Q2 (through buffer/level shifter A1U4F), which provides
drive current for the +24 VDC transverse and longitudinal electromagnets. The
magnets release the mechanical brakes allowing tabletop "float" motion. After 47
seconds, A1U6B times out and A1Q1 turns off. Releasing the FLOAT foot pedal or
push button before 47 seconds will cause a low level to be applied to A1U6B-13,
thereby resetting A1U6B and turning off A1Q1 and A1Q2. The magnets de-ener-
gize and the fail-safe brakes lock, preventing tabletop "float" motion.
Foot Pedal Disable Switch
Foot Pedal Disable Switch S14 is located below the table rail on the left end of the
table. Pressing the switch until the PEDAL DISABLE SWITCH lamp DS2 is illumi-
nated disables foot pedal operation via comparator A1U5A. When the patient is
in the correct location for x-ray, disabling the foot pedals prevents inadvertent
activation of the pedals. When the Foot Pedal Disable Switch lamp DS2 is not illu-
minated, the foot pedals are fully operational.
Positive Beam Limitation
When the table is used in a PBL system, the UP LIMIT signal is used to prevent
exposures when the table is not in its full up position (i.e., at 40" SID). Relay
A1K7 is energized when the table is at its maximum up position (as indicated
when the /UP LIMIT signal is active low) to indicate the 40" SID position via relay