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What This Guide Helps With
This guide helps troubleshoot Err 386 on a CONMED System 2450 / 5000 Series electrosurgical unit when the generator fails startup POST because the high-voltage DC supply cannot reach the required 140V test level.
Err 386 points toward a high-voltage supply startup problem. Possible causes include poor input power, external accessory influence, internal cable issues, RF Amplifier loading, HVPS failure, Controller command issues, or related internal wiring faults.
Step-by-Step Troubleshooting
Ensure Patient Safety First
- Do not use the ESU for a patient procedure while Err 386 is active or unresolved.
- Remove the ESU from patient use.
- Disconnect any active handpiece, return electrode cable, footswitch, bipolar accessory, or adapter cable from the clinical setup.
- Provide staff with a known working ESU if electrosurgery is still needed.
- Label the unit for Clinical Engineering evaluation.
Err 386 indicates the generator is not passing an internal high-voltage supply check. The unit should not be trusted for clinical output until the fault is resolved and required testing is completed.
Verify the Reported Error and Behavior
- Power the ESU on in a safe non-patient-care setting.
- Confirm the exact displayed error is Err 386.
- Observe whether the error appears during startup POST, intermittently, after accessories are connected, or after the unit has been moved, cleaned, or recently serviced.
- Record whether the error is repeatable or only happened once.
This confirms the issue is a true system-reported startup fault and not a misreported user setup issue.
Translate the Error Into the Real-World Failure
- Err 386 means the ESU attempted to bring the high-voltage DC supply up to the POST test level of approximately 140V, but the supply remained too low.
- This may indicate the high-voltage power supply is not starting correctly.
- It may also indicate the RF Amplifier is loading down the HVPS.
- Other possible causes include a Controller command issue, loose internal cable, damaged internal wiring, HVPS failure, RF Amplifier failure, or Controller assembly failure.
This error is not usually caused by a bad pencil or return pad cable alone. It is related to the internal high-voltage supply path.
Check External and Simple Causes First
- Verify the ESU is plugged into a known good hospital-grade outlet.
- Check that the power cord is fully seated and undamaged.
- Inspect the plug, cord strain relief, and rear power entry area for looseness, damage, discoloration, heat marks, or contamination.
- Power cycle the unit fully by turning it off, waiting briefly, and turning it back on.
If the unit powers on normally and Err 386 does not return, continue functional checks per facility policy before returning it to service. If the same error repeats, continue troubleshooting.
Remove External Accessories and Retest
- Disconnect all external accessories from the ESU.
- Remove the active electrode pencil or handpiece.
- Remove the return electrode cable.
- Disconnect the footswitch.
- Disconnect bipolar accessories, adapter cables, and any specialty accessories.
- Power cycle the ESU again.
If Err 386 clears, one of the connected accessories or cables may have contributed to the condition. If Err 386 remains, the problem is likely internal to the generator.
Inspect the ESU for Physical or Environmental Issues
- Inspect the generator for liquid intrusion or cleaning residue near connectors.
- Check for burning smell, unusual fan noise, impact damage, or visible case damage.
- Verify front and rear panel connectors are not loose or damaged.
- Confirm ventilation is not blocked.
- Look for signs the unit was dropped, transported roughly, or exposed to fluid contamination.
Physical damage, fluid intrusion, contamination, or blocked airflow can contribute to internal power faults.
Power Cycle and Confirm Whether Err 386 Repeats
- With external accessories removed, cycle system power again.
- Observe whether Err 386 returns during POST.
- If the error clears, continue facility-required ESU testing before return to service.
- If Err 386 repeats, continue with bench evaluation.
A one-time POST failure may clear after reset, but a repeated Err 386 indicates a persistent high-voltage supply problem.
Observe HVPS LED2 During POST
- With the unit on the bench and following facility safety procedures, observe LED2 on the high-voltage power supply during POST.
- Note whether LED2 illuminates normally during the POST sequence.
- Note whether LED2 fails to illuminate when the fault occurs.
LED2 behavior helps determine whether the HVPS is attempting to come up or is being prevented from operating normally.
Isolate Possible RF Amplifier Loading
- If LED2 does not illuminate during POST, disconnect the cable between the HVPS and RF Amplifier as allowed by service procedure.
- Retest power-up behavior.
- If LED2 illuminates after the RF Amplifier is disconnected, suspect the RF Amplifier is loading down the HVPS or has failed.
- If LED2 still does not illuminate, suspect the HVPS, Controller, control signal, or related cabling.
This step helps separate a weak or failed HVPS from a downstream RF Amplifier problem.
Verify Internal Cable Connections
- Inspect and reseat accessible internal connections related to the HVPS, RF Amplifier, and Controller assembly.
- Check for loose connectors, damaged pins, partially seated plugs, heat discoloration, chafed wiring, pinched wiring, arcing, or contamination.
- Correct any obvious cable seating or wiring issue before replacing boards.
A poor connection in the HVPS control or output path can cause a low supply condition during POST.
Verify HVPS Control Signals and Output
- Using the appropriate service procedure and test mode, verify that the HVPS is receiving proper control signals from the Controller.
- Check whether the HVPS output behaves as expected during the test sequence.
- If control signals are present but output does not rise correctly, suspect the HVPS or downstream loading.
- If control signals are missing or incorrect, suspect Controller, cabling, or control path failure.
Err 386 may be caused by the HVPS itself, the RF Amplifier loading the supply, or the Controller failing to command the supply correctly.
Determine the Most Likely Fault Area
- Suspect the RF Amplifier if LED2 illuminates after the RF Amplifier is disconnected, Err 386 occurs only when the RF Amplifier is connected, and cabling to the RF Amplifier checks good.
- Suspect the HVPS if LED2 does not illuminate, HVPS output remains low, and control signals are present but output does not rise correctly.
- Suspect the Controller or control path if the HVPS output is low because control signals are missing or incorrect while cabling checks good.
- Suspect related wiring if connector, pin, heat, arcing, or cable damage is found during inspection.
Proper isolation prevents unnecessary board replacement and avoids guessing.
Stop When Resolved
- If a loose cable, accessory issue, power issue, or confirmed component fault is corrected, reassemble the ESU properly.
- Repeat startup POST.
- Confirm Err 386 no longer appears.
- Perform required ESU safety and performance testing per facility procedure.
- Verify output and alarm behavior before returning the unit to service.
- Return the device to service only after it passes all required checks.
If the Problem Persists
If Err 386 continues after power, accessories, external condition, cabling, RF Amplifier loading, HVPS behavior, and control signals have been checked, external and common causes have been ruled out.
A persistent Err 386 strongly indicates an internal generator failure involving the HVPS, RF Amplifier, Controller assembly, or related internal wiring.
The device should be removed from service, labeled Out of Service, and sent for repair or further bench evaluation.
Do not return the ESU to clinical use with an unresolved Err 386.
Clinical Use Tip
Never troubleshoot an ESU with an active patient connected. If Err 386 appears before or during a procedure, have staff obtain a working backup generator before any troubleshooting continues. Do not rely on a generator that fails high-voltage POST testing, even if the fault clears once.
Work Order Documentation (CCR Method)
CCR = Complaint, Cause, Resolution
Complaint
What was reported by the clinical staff.
Example:
"CONMED System 2450 / 5000 Series ESU reported Err 386 during startup. Unit failed POST with HVDC to 140V supply too low condition and was not available for clinical use."
Cause
What was observed during troubleshooting.
Example:
"Err 386 was verified during POST. External accessories and power source were checked. Fault condition indicates the high-voltage DC supply could not reach the required POST level. Further isolation pointed toward possible HVPS, RF Amplifier loading, Controller signal issue, or internal cabling fault."
Resolution
What action was taken.
Example:
"Removed ESU from service and labeled Out of Service. Power cycled unit, removed accessories, inspected power cord and external condition, and verified Err 386 repeated during POST. Bench evaluation performed to observe HVPS LED2 behavior and isolate HVPS/RF Amplifier/Controller path. Unit referred for repair or component-level service as required. Final status documented as not returned to service until repair and full ESU performance testing are completed."
Helpful Details to Include (If Known)
- Alarm behavior
- Accessories swapped
- Power behavior
- Environmental factors
- Indicator lights
- Final device status
Final Thought
Err 386 should be treated as a high-voltage startup failure, not a simple user setup issue. Good troubleshooting starts with patient safety, confirms the reported error, rules out external causes, and then logically isolates the HVPS, RF Amplifier, Controller, and cabling. Clear CCR documentation helps the next technician understand exactly what was checked, what was found, and why the device was removed from service or returned after repair.
That is successful troubleshooting.