ABB 266 MODBUS User Manual page 83

NOTICE – Reverse polarity protection. Transmitter circuitry is designed to protect the transmitter if the power
supply polarity is reversed.
A determination that the power supply positive and negative wires were reversed does not necessarily indicate that
the termination block has been damaged.
4. If a correction was made to the power supply terminations, reconnect power to the transmitter and observe the LCD
screen. If the LCD is now visible and operational, continue to the next step. Otherwise, go to section 6.2.3, Verifying HMI
connector viability.
5. Secure the housing cover using instructions in section 5.2.2, Securing the housing cover, to secure the unit, and return the
transmitter to operation.
Verifying HMI connector viability
If the electronics module has recently been replaced, the LCD assembly removed or replaced, or the DIP switches have been
accessed, it is possible that the HMI connector is missing or was damaged.
1. Inspect the HMI connector if installed (go to section 5.5, Replacing the HMI connector).
2. If no HMI connector is installed, install a new connector.
3. If the HMI connector appears damaged, replace the connector with a new or undamaged one.
Verifying component viability
If prior attempts to troubleshoot a blank LCD screen have not identified the problem, the LCD assembly or terminal block should
be replaced. The following instructions provide the steps for replacing these assemblies.
WARNING – Bodily injury. When the housing covers are removed and power is still connected, there is a
potential for explosion. Failure to observe this safety information may result in death or severe injury.
Do not remove housing covers in hazardous (classified) areas or explosive environments unless the area is
known to be non-hazardous. Verify an explosive atmosphere is not present before removing the housing covers
when power is live.
This procedure requires the transmitter to remain powered up.
1. If the wiring at the power supply terminations was correct, the LCD contrast was reset to factory defaults, and the screen is
still blank, the LCD assembly should be replaced. Go to section 5.4, Replacing the LCD assembly, for replacement
instructions. If the LCD is now visible, go to step 4.
2. If the LCD assembly has been replaced and the LCD screen is still blank, the terminal block should be replaced. Go to
section 5.7, Replacing the terminal block, for replacement instructions. If the LCD is now visible, go to step 4.
3. If the terminal block has been replaced and the LCD screen is still blank, contact customer service. Customer service
contact information may be found in section 6.4.2, Customer services.
4. Secure the housing cover using instructions in section 5.2.2, Securing the housing cover, to secure the unit, and return the
transmitter to operation.
5. Verify the LCD is displaying correctly.
266 MODBUS® multivariable transmitter User manual 2105216 Rev. AB | 75
6 Troubleshooting