Loma IQ2 Service Manual page 99

DC POWER SUPPLY RAILS
The continuous monitoring of the basic DC power rails required to operate your
detector is another function of the fault monitoring circuits.
In the unlikely event of any of the primary +12V, -12V analogue (AN) or +5V
digital (DIG) rails go out of specification a "System fault" is generated resulting in
the same sequence of events as generated by an OSGO failure.
The voltages can be checked for specification as follows:
1. Using the 5mm allen key supplied with your equipment, unscrew the 2 front hinged
door screws on the control box and open the door.
2. Using the DMM set on the 20V range or equivalent measure the voltages at the
links between JP305 and JP5 on the control board with respect to their own ground
connection. The links are located underneath the Serial Link Board. If this board is
fitted, it will need to be temporarily removed.
Primary Rail
+ 5V Pin 1 (ref. Pin 2)
+ 5v ground Pin 2
+/- 12V grounds Pin 3
+ 12V Pin 4 (ref. Pin 3)
- 12V Pin 5 (ref. Pin 3)
+ EXT Pin 6 (ref. Pin 7)
- Ext (ground) Pin 7
1. Adjustment can only be made to the +/- 12V rails using RV1 located in the
power supply area of the control board. Refer to
"Maintenance" section of this manual for its location.
2. If either rail is not present then protection fuse may be open circuit see
12v DC Rail Protection Fuses
manual for information.
3. Adjustment is carried out by connecting a DMM set on the 200V DC range
with the positive probe connected to Pin 4 and the other to Pin 5. RV1 Is
adjusted until the reading is 24V.
4. To ensure each rail is within its individual specification check each rail in turn
with respect to Pin 3 (+/- 12v ground). Minor adjustment to RV1 may be
required.
Module 9095
Nominal Voltage Upper Tolerance
5.00 5.25
12 12.60
12 10.80
12 10.80
on page 11
Functional Testing
Lower Tolerance
4.75
11.40
13.20
13.20
Figure 2
on page 6
in the "Maintenance" section of this
in the
+/-
7-7