Is the backlight on? Under the illumination of the flashlight, one can vaguely see the content of the image ->the backlight burns out; No display at all → motherboard/LCD malfunction.
2. Unable to communicate with PLC
Step check item handling method
Is the power supply normal and has GP been started? —
Does the wiring of the communication cable comply with the pin definition of COM1/COM2? Especially RS-422 must be connected to terminal resistors and short circuited control lines (CSB-ERB, CSA-ERA).
Are the protocols and drivers for devices/PLCs in Pro Designer 3 correct? Reconfirm and download.
Are the communication parameters (baud rate, data bits, stop bits, parity check) consistent with the PLC? Adjust consistently.
If RS-232C is used, is SG connected? SG must be connected, otherwise the interface may be damaged.
3. Touch unresponsive or offset
Go to Offline → Self Test → Touch Panel, press each intersection point one by one, and check if each position can be correctly identified. If there is no response or significant displacement in certain areas, the touch screen may be damaged.
If the touch fails and the backlight is burned out, the "Enable Touch if Backlight is OFF" is set to OFF, and the touch is already disabled. This is normal protection.

Detailed explanation of Self Test function
Enter Offline → Self Test to perform five diagnostics:
The role of the test item is achieved through standard failure strategies
Char. Pattern check font ROM and Chinese character ROM display OK firmware damage, needs to be sent for repair
Disp Pattern check: The drawing function is displayed as OK, but there is a test pattern or LCD driver malfunction on the screen
Touch Panel touch screen matrix test highlights that the touch screen is broken when touching each grid and needs to be replaced
COM1/COM2 serial port circuit testing requires a dedicated loopback plug, and if it displays OK, check the wiring and driver chip
Video Memory: Video Memory Test OK. Video Memory: Bad, motherboard malfunction
Self made method for serial port loopback plug (for Self Test):
COM1 (25 pin female): Short circuit # 2 (SD) and # 3 (RD); #Short circuit between 4 (RS) and # 5 (CS); #20 (ER) and # 6 (DR) are short circuited.
COM2 (9-pin male): Short circuit # 2 (RD) and # 3 (SD); #Short circuit between 7 (RS) and # 8 (CS); #4 (ER) and # 6 (DR) are short circuited.
Please refer to section 5.2.2 of the manual for detailed illustrations.
Complete Guide for Backlight Replacement
When the status LED displays orange and "Enable Touch if Backlight is OFF" is set to OFF in Offline, the screen touch is disabled. At this point, the backlight must be replaced.
Security Warning:
Before replacement, the power cord must be unplugged and wait for at least 10 minutes for the lamp and inverter to cool down to prevent burns.
The backlight glass tube is fragile, do not touch the glass or pull the leads. If accidentally broken, be careful to clean the debris (containing mercury) and avoid inhalation or contact with the skin.
Backlight model comparison:
GP model backlight order number
GP‑2400T‑C41‑24V PS400‑BU00‑MS
GP‑2500SC‑41‑24V PS500S‑BU00
GP‑2500T‑C11 / GP‑2500T‑C41‑24V GP577RT‑BL00‑MS
GP‑2600T‑C11 / GP‑2600T‑C41‑24V PS600‑BU00
GP-2500L users are non replaceable and must contact an authorized service provider
Replacement steps (taking GP-2500T/2600T as an example):
Turn off the power, unplug all cables, remove the GP from the panel, and place the screen facing down on the soft cushion.
Use a Phillips screwdriver to remove the fixing screws of the back cover and take off the back cover.
Find the backlight tube assembly (usually located on the top, bottom, or left and right edges of the LCD panel). Unplug the high-voltage connection wire of the lamp (note: residual high voltage, it is best to wear insulated gloves).
Carefully remove the old lamp tube and clean the dust in the lamp tube slot.
Push the new lamp tube completely into the slot and reinsert the high-voltage wire.
Reinstall the back cover and tighten the screws (torque 0.5 N · m).
Power on test: The status LED turns green and the screen brightness returns to normal. If the LED is still orange, check the connection or tube direction.
Backlight lifespan: Design lifespan of 50000 hours (continuous illumination at 25 ℃ environment, brightness attenuation to initial 50%). The actual lifespan is affected by environmental temperature and switch frequency. It is recommended to replace it proactively after 5 years to avoid sudden failure and production line shutdown.
Regular maintenance checklist and battery precautions
Check every six months:
Whether the environmental temperature and humidity meet the specifications.
Is the power supply voltage within the allowable fluctuation range.
Are the communication cables and power terminals loose.
Is the installation of fasteners still secure.
Check for cracks, hardening, or warping in the installation gasket.
Lithium battery (for data backup):
The battery model is not provided in the manual, but it is stated that the battery life is 10 years below 40 ℃; 4.1 years below 50 ℃; 1.5 years below 60 ℃.
When fully charged, data can be retained for about 60 days; About 6 days in semi charged state.