31
Model 764 Differential Pressure Transmitter
Section 4
Troubleshooting
!
WARNING: Except for cleaning the DPU and replacement of O-rings, fas-
teners, and connector assemblies, no field repair or component replace
-
ment on the Model 764 transmitter is authorized. Unauthorized repairs
void any certification to qualification reports for design basis event
performance.
Table 4.3—Troubleshooting
Problem
Possible Source
Probable Cause
Corrective Action
No Output
Power Source
Blown fuse, faulty
component
Replace fuse, repair power
supply
Transmission
Cable
Loose terminal con-
nection
Tighten terminal connection;
locate and replace broken
wire
Receiver (or load)
Blown fuse, faulty
component
Replace fuse; repair or
replace receiver or load
Transmitter
Loose terminal,
reversed power
connection, faulty
component
Tighten terminal, reverse
power connection, return to
factory for repair
Transmitter
"zeros" but
cannot get
full output
Power Source
Low voltage
Repair power source
Load Resistance
Resistance too high
Replace load resistance or
repair as required
Transmission
Cable
Resistance or length
of cable in excess of
specifications
Measure cable loop
resistance and bring within
specifications
Electronic Module
Loss of gain
Return to factory for repair
Range Selector
Wrong connection or
terminal resistance
increased
Check circuit and operating
procedure for range selector;
clean and tighten terminal
connections
Strain Gage Beam
Physical damage
Return to factory for repair
Pressure Line
Loose fitting, broken
tube or valve
Determine source by closing
valves and monitoring for
pressure decay
Out of
Calibration
Electronic
Component shifted
Return to factory for repair
Erratic
Operation
Terminal
Connections
Loose or dirty
Tighten and/or clean as
required
Electronic
Component
Intermittent
Check connector assembly
- these are field replaceable
as a complete assembly only,
any other repair requires fac-
tory service
Strain Gages
Physical damage
Return to factory for repair
