Service manual

PN 4237242C
2.4-10
INSTRUMENT DESCRIPTION
SYSTEM CONTROL
At power up, the programmable logic device is reset, which clears all latches. This causes Q4
to conduct, grounding the POWER ON signal. The system remains in this state with the
+24 V off until the instrument’s software is loaded and turns on the +24 V.
+24 V POWERFAIL (PF/PG) Signal
The +24 V power supply outputs a POWERFAIL signal. This signal indicates failure to
produce +24 V within factory-set limits, a brownout of at least 38 ms, or a temperature
overload on the supply. The MD II Series monitors this signal. The signal is connected to a
latch on the Motor/Solenoid Driver card. This latch is part of a programmable logic device
and is polled by the instrument software when it does a +24 V power supply check. It is
important to realize that the latch remains set even after the condition that caused it to be set
goes away.
Inputs
Outputs
Table 2.4-5 Motor/Solenoid Driver Card Input Connections
Connector Connected To
J1 DRA2, J1
J2 DRA2, J2
J3 DRA2, J3
J4 DRA1, J1
J5 DRA1, J2
J6 DRA1, J3
J15 +24 V, POWER ON, POWERFAIL
J18 Resistor bank
J23 Resistor bank
Table 2.4-6 Motor/Solenoid Driver Card Output Connections
Connector Connected To
J7 Solenoid Interconnect card
J8 Peristaltic pump motors
J10 Syringe Assembly and traverse motor
J11 Flex Connect card
J12 Not used