The Problem
An Agilent 6890 GC could no longer communicate reliably with its ChemStation workstation. Cable and software checks did not explain the repeated connection failures, pointing to faults in the instrument electronics.
Board-Level Diagnostics
ScientifiCo evaluated the LAN interface card, logic controller, and connected electronic pneumatic control assembly. The main processors on the communication and logic boards were re-soldered to restore compromised connections, and the assemblies were tested in-house.
When the failures returned after reconnection, the fault was traced beyond the rebuilt boards to a defective EPC board that was damaging connected logic electronics. Isolating that upstream cause prevented another incomplete repair.
Electronic Repair and Rebuild
The failed EPC board was replaced, and the affected interface and logic boards were rebuilt again. The FID interconnect PCB was also replaced, and related autosampler wiring and control connections were corrected before reassembly.
Verification
After the electronic repairs, the GC initialized correctly, established stable communication with the control software, and passed operational checks. The autosampler and tray were also verified through software-controlled injection testing.
Result
Board-level rework and system-level fault isolation returned the Agilent 6890 GC to working condition without replacing every affected module. The repair restored reliable startup, communication, and sample-handling operation.
