Easylite Na/K: K+ channel shows ***** after calibration
What happened
After calibration the analyzer returned asterisks instead of K+ values while Na+ measured normally; the diagnostics menu showed no contact on the K+ channel.
What was checked
- Replaced the K+ electrode and rechecked the channel.
- Rang out the circuit from the K+ connector to the measurement board.
- Reseated the ribbon cables in the electrode module.
- Cleaned the contacts on the sample detector.
- Watched the K+ channel state in the diagnostics menu while working the electrode block.
Cause
Not established for certain. The engineers suspected a poor contact in the K+ path: wiggling the electrode block temporarily brought the channel back, which points to an intermittent connection that settled after the module was reworked. Warm-up and stabilisation were also suggested as an explanation, but since the analyzer had not been switched off, that stays unconfirmed.
What was done
The engineers replaced the K+ electrode, rang out the circuit from the K+ connector to the board, reseated the ribbon cables and cleaned the contacts on the sample detector. As reported in the case, the analyzer returned to normal K+ readings after about two hours of operation; the exact root cause remained unclear, so treat this fix as probable rather than proven.
Safety
De-energise the analyzer and follow biohazard precautions around the sample path and probe contacts — treat all touched surfaces as potentially infectious and disinfect before returning the unit to use.
Lesson: When one ISE channel drops out with no contact in diagnostics, work the entire connection path — electrode, connector, cables, detector contacts — because an intermittent contact can mimic a dead electrode and may only settle after the whole module is reworked.
Covered in the course: Lab Analyser Service — Level 2: Fault-Finding →
Written from an anonymised case shared by service engineers. It is not a manufacturer instruction and grants no authorisation. Independent note; names are trademarks of their owners.