Quantum QT-740, Руководство по обслуживанию

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Chapter 3 Theory of Operation
Models QT-740 & QT-750 - Service Manual
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through diodes A1D18 and A1D17 to A1U4B and A1U4D, respectively, de-energiz-
ing A1K1, A1K3 and A1K4. When A1K1 or A1K3 are de-energized along with
A1K4, operation of the DC motor is disabled. The +24 VDC output is supplied to
15-volt regulator A1U7, which produces reg15 VDC. The +15 VDC is
input to regulator A1U8, which pr5 VDC for the 6-Way Table Control
Board components.
Table Up Motion Control
When the UP foot pedal is depressed, switch S1 contact is connected to ground.
The ground is applied through 6-Way Table Control Board connector A1J2-1 as an
active low /UP signal, which is input to NOR gate A1U2A. This produces a high
output at A1U2A-1, which is inverted low by A1U4B. The output from A1U4B
energizes the coil of UP relay A1K1 through 150 ms delay circuit A1U1A, A1C5,
A1R5, A1R6, and A1U4A1U4A. (Since A1U4B's output is a low-going signal, A1C5
discharges in approximately 1 millisecond through A1D2 and A1R5, which imme-
diately energizes A1K1). When A1K1 is energized, the CONTROLLER(-) signal
from DC Motor Driver Board A2 is connected to the DC motor (through A1J1-10)
as the MOTOR signal. The low-going signal from A1U4B is also applied to A1D10
(through A1D9) and A1R21 to discharge A1C9 to a voltage level that will cause
the output of A1U1C to go low in approximately 150 milliseconds. This energizes
A1K4, which removes the connection from A1J1-1 and A1J1-9, thus allowing the
DC motor to rotate. The INHIBIT outputs are applied through A1J1-9 and A1J1-1
to DC Motor Driver Board A2 H1 and H2 terminals. Relays A1K5 and A1K6 are
also energized in a similar fashion, which releases the Motor Brake and redundant
Table Brake. The delay of 150 milliseconds allows A1K1 to energize before A1K4
energizes. A similar sequence occurs in reverse when the UP foot pedal is
released; A1K4, A1K5, and A1K6 are de-energized in approximately 1 millisecond,
then A1K1 is de-energized approximately 150 milliseconds later. At the same
time, the /DN signal applied through connector A1J2-11 is inactive high, and
DOWN relay A1K3 is de-energized (through components A1U2C, A1U2D, A1U4D,
A1U1B, A1U4C). As a result, the CONT) signal from DC Motor Driver
Board A2 is routed to the DC motor (through A1J1-12) as the MOTOR+BRK RES
signal. This causes the motor to drive the Scissors Assembly upwards. (The
brake resistor is not actually applied across the motor when it is driving up,
DOWN relay A1K2 must be energized as described to connect the braking resis-
tors to the motor during table down motion.)
Table up motion is stopped in any of the following ways:
• When the UP foot pedal is released, the /UP signal returns to an inactive
high level, de-energizing UP relay A1K1 through A1D21, A1U4B, A1U1A,
and A1U4A and INHIBIT relay A1K4 through A1U2A, A1U4B, and A1U1C.
When de-energized, the CONTROLLER(-) input is open, disabling the DC
motor. Releasing the UP foot pedal before 24 seconds will cause a low
level to be applied to A1U6A-3, thereby resetting A1U6A and stopping
tabletop vertical motion.
• After 24 seconds from the time the active low /UP signal was first
applied, the output at one-shot A1U6A-6 returns to a low level. (A1U6A