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6 Replacement procedures
6.1 Replacing the flowcell PCB housing gasket,
PCB housing cover and PCB
Part numbers:
— AW502 228 flowcell PCB housing gasket
— AW502 227 flowcell PCB housing cover
— AW502 225 PCB assembly
Referring to Fig. 6.1:
1. Remove and retain 4 flowcell PCB cover fixing screws and
washers A and remove PCB cover B.
2. Remove flowcell PCB housing gasket C. If replacing the
gasket, discard.
3. If replacing PCB assembly D, disconnect all cables
from the terminal block on the PCB assembly, loosen all
cable glands then remove cables.
It is necessary to partially remove the glands, blanking
plugs and the LLDO connector to remove PCB assembly
D.
4. Remove and retain 2 PCB fixing screws and fibre washers
E and remove PCB assembly D. Take care not to lose
2 spacers F fitted on the screw threads behind the PCB
assembly.
IMPORTANT (NOTE)
To secure the new PCB into the flowcell PCB
housing, pass 2 PCB fixing screws and fibre
washers E through the PCB mounting holes, fit
the spacers F onto the screw threads.
5. Carefully offer PCB assembly D up into the flowcell PCB
housing and tighten 2 PCB fixing screws.
6. Remake cable connections (disconnected at step 3) – refer
to Fig. 6.2 and Table 6.1 for terminal connections.
7. Tighten the cable glands, plugs and LLDO connector into
the flowcell PCB housing to ensure a watertight seal.
4
INS/ANAINST/025-EN Rev. B | Navigator ADS551 | Low level dissolved oxygen | Replacement / Upgrade procedures – wet section spares
8. Refit, or for new items, fit flowcell PCB housing gasket C
and cover B using 4 PCB cover fixing screws and
washers A. (Ensure flowcell PCB gasket C is located
correctly.)
F
A
Fig. 6.1 Replacing the flowcell PCB housing gasket, PCB housing and PCB
TB1
TB3
White
Screen
Red
Black
Green
Black
Red
Serial (Tx)
cable
Fig. 6.2 Cable connections to transmitter – ADS551
Cable
Color
Serial
White
Green
Screen
Black
Red
Drain valve
Red
Black
Temp sensor
White
Screen
LLDO sensor
Red
Blue
Flowmeter
Red
Brown
Black
Table 6.1 Cable connections to transmitter – ADS551
E
D
C
B
TB5
TB4
TB2
Screen
Blue Red Brown Black
White
Red
Temp sensor
Drain valve
cable
cable
Terminal
Description
block ID
Data –ve
Data +ve
TB1
Screen
0 V
24 V
+ve
TB3
–ve
Pt1000
TB5
Pt1000
+ve LLDO sensor
TB4
–ve LLDO sensor
+ve
TB2
GND
–ve
Flow-
meter
cable
LLDO
cable
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