-
E-mail
hn17@163.com
-
Phone
15931739111
-
Address
Hongnuo Instrument
Tianjin Hongnuo Instrument Co., Ltd
Maintenance Example Sharing: Maintenance of Constant Humidity and Temperature Incubator with No Display on Startup
Date: 2025-09-22Read: 0
Constant humidity and temperature incubatorIf there is a malfunction of "no display (black screen)" when the incubator is turned on, it often leaves the user at a loss. This article uses a real repair case to disassemble and investigate the logic and solutions, helping to quickly locate the root cause of the problem.
1、 Description of fault symptoms
A certain brand of incubator (model: HWS-300) in a certain laboratory, after being powered on, the power indicator light does not light up, the LCD screen of the control panel is not displaying, and the buttons are unresponsive. However, a slight rotation sound of the internal fan can be heard (indicating that some circuits are powered on).
2、 Preliminary investigation: power supply and fuse
The maintenance personnel first check the external power supply: measure the output voltage of the socket with a multimeter to be 220V (normal), confirm that the power cord is not damaged and the plug is in good contact. Open the junction box on the back of the incubator and check that the input voltage of the power module is 220V (normal), but there is no voltage output at the output terminal (+24V,+5V DC to the control board) - it is preliminarily judged that the fault point is in the power module or fuse.
Further check the fuse next to the power module (usually 2A slow melting type): Measure with a multimeter in resistance mode and display "OL" (open circuit state) to confirm that the fuse has blown. After replacing the fuse with a new one of the same specifications and powering it back on, the fuse instantly melted again - indicating a short circuit fault in the power module (not a simple fuse issue).
3、 Deep maintenance: power module and control board
Disconnect the power supply, open the right side panel of the incubator, and expose the power module (independently packaged switch power supply). Measure the ground resistance of the primary coil (220V input terminal) of the power module with a multimeter, which is 0 Ω (normally>100k Ω), indicating that there is a short circuit in the primary circuit. Upon careful inspection, it was found that the pin of a rectifier diode (model: 1N5408) in the power module had poor contact with the heat sink, resulting in a local short circuit (the current was unlimited after the diode broke down, burning the fuse).
Replace the rectifier diode of the same model and re fix the heat sink with thermal grease. Subsequently, the power module was tested: after inputting 220V, the output voltage of+24V (for the main chip of the control board) and+5V (for the buttons and display screen) returned to normal (24.2V and 5.1V, respectively, with an error within ± 5%). Reinstall the control board, turn on the power and the LCD screen will light up, displaying the initial temperature/humidity value (25 ℃/60% RH). The button operation response is normal, and the fault has been resolved.
4、 Experience summary
The common causes of such "no display" faults are ranked as follows: blown fuses (accounting for 40%, mostly due to short circuits or overload of power modules), abnormal power input of the control board (accounting for 30%, such as missing output voltage of power modules), damage to the display screen itself (accounting for 20%, usually accompanied by flickering backlight or unresponsive buttons), and motherboard chip faults (accounting for 10%, less common). It is recommended to prioritize checking the power path (fuse → power module → control board input voltage) during maintenance, and then gradually investigate downstream components.
For laboratory users, daily useConstant humidity and temperature incubatorIt is necessary to avoid frequent power on and off (to prevent voltage surges), regularly clean the dust of the power module (to prevent poor heat dissipation from causing component aging), and do not disassemble the power module by yourself when encountering no display faults (high voltage danger). Professional engineers should be contacted in a timely manner for handling. Through this case, we not only solved the problem, but also mastered the system maintenance logic of "from phenomenon to root".