c. For HART communications, the power supply voltage must be at least 18 Vdc.
3. Be sure the HART communicator is properly connected.
a. The communicator leads must be connected across the load.
b. The communicator can be connected across the power terminals (TB-15 and
TB-16).
4. Verify that the 375 or 475 is working correctly by testing it with another HART Smart
device.
a. If the communicator is working, the transmitter electronics may have failed. Call
Rosemount for assistance.
b. If the communicator seems to be malfunctioning, call Rosemount at 800 999
9307 for assistance.
No display
1. Be sure power requirements are being met.
a. The positive voltage lead must be connected to TB-16.
b. Check dc voltage requirements and load restrictions.
2. Check for bad connections between the circuit boards. Be sure the ribbon cable
between the display and CPU boards is firmly seated in the socket on the CPU board.
Be sure the socket connection between the CPU and analog boards is firm.
Display segments missing
Replace the display board.
Transmitter locks up
1. Turn the dc power off; then turn it back on.
2. If the problem persists, replace the electronic board stack (PN 23992-02, HT; PN
23992-03, FF).
Transmitter periodically restarts itself.
If the transmitter periodically restarts itself, complete the following steps.
1. The problem is usually related to improperly wired RTD input terminals.
a. The RTD return wire must be connected to TB-3. The RTD sense wire must be
connected to TB-4, and the RTD in wire must be connected to TB-5. If the pH
sensor does not have an RTD, connect a jumper wire across the terminals TB-3
and TB-4 and a second jumper across TB-4 and TB-5.
b. If the RTD connections have been jumpered as described in step a, automatic
temperature compensation must be turned off and the transmitter operated in
manual temperature mode.
2. If RTD wiring is correct and problems still persist:
a. Monitor the power supply. Be sure the power is not intermittent and the correct
voltage is present.
Diagnostics and troubleshooting
Instruction Manual 73
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