During distillation on a Kjeltec 8400, the instrument suddenly powered off and restarted automatically.
The issue occurred intermittently during steam generation. In some cases, the display turned off completely for a few seconds before rebooting.
Symptoms
- Instrument shuts down during distillation
- Random reboot during operation
- Water pump low level alarm may appear afterward
- Titration LEDs blinking rapidly
- Clicking sound near power section
- Problem appears more frequently during heavy steam operation
Initial inspection
The instrument had signs of previous steam leakage inside the chassis. Dust contamination was also found around the main board and power section.
A modified circuit breaker had been installed instead of the original fuse holder. This raised suspicion of unstable power protection and electrical noise.
The following components were inspected:
- Power supply unit
- EMI filter
- Main board
- RACM board
- Steam generator connectors
- Grounding condition
Possible causes
Several possible causes were considered during troubleshooting:
1. Unstable power supply
Steam generation creates high electrical load. Weak grounding, unstable input voltage, or improper fuse modifications may cause unexpected rebooting.
2. Steam leakage contamination
Long-term steam leakage may create conductive residue and corrosion around connectors or PCB areas.
3. Main board damage
Burn marks or damaged IC areas near valve or motor control circuits can create unstable operation during distillation.
4. Connector overheating
The steam generator heater connector should be inspected carefully. Overheated connectors are a known issue on older systems.
Troubleshooting performed
The following actions were performed during field service:
- Internal cleaning
- Connector inspection
- EMI filter replacement
- Main board replacement test
- Grounding inspection
- Isolation testing with disconnected peripherals
- Power supply voltage measurement
The PSU output remained stable at approximately 24V DC during testing.
Result
After inspection and replacement of damaged components, the instrument operated normally without unexpected shutdown during repeated distillation cycles.
This case showed that power instability and contamination from previous steam leakage can create intermittent reboot symptoms on older Kjeltec 8400 systems.
