Yuken’s power amplifiers drive spool or pilot position on a wide range of proportional valves, including the EFBG, EBG, and EHFBG series. When a system starts misbehaving, it’s tempting to swap the amplifier first — but a meaningful share of complaints trace back to wiring, power supply, or valve-side issues rather than a failed amplifier. Here’s what to check before ordering a replacement.
Verify Supply Voltage and Grounding
Yuken power amplifiers are sensitive to supply voltage stability and clean grounding. Voltage sag under load, a shared ground with noisy equipment, or a loose chassis connection can all produce symptoms that mimic a failing amplifier — erratic output, instability, or resets that only appear once the rest of the machine is running.
Confirm the Command Signal at the Source
Before assuming the amplifier itself is at fault, verify the command signal reaching it matches what the controller intends to send — correct voltage or current range, correct polarity, and no signal degradation along the cable run. A damaged cable or an issue with the upstream controller can produce symptoms identical to a failed amplifier.
Check Coil Resistance Against Specification
Yuken proportional valves are rated for specific coil resistance values, and using an amplifier configured for the wrong coil resistance range will produce inconsistent or unstable output even when both the amplifier and valve are individually functional. Confirming the coil resistance matches what the amplifier is set to expect is a quick and often overlooked check.
Inspect for Physical and Heat Damage
Open the enclosure and check for discoloration, bulging capacitors, or burn marks around connectors and components. Amplifiers mounted in poorly ventilated enclosures or exposed to vibration are prone to solder joint fatigue, which can cause intermittent faults that appear only once the unit has warmed up during normal operation.
When It’s Time for a Real Repair
If supply voltage, command signal, and coil resistance all check out and the fault still follows the amplifier, it likely needs bench-level diagnostics rather than a guess-and-swap replacement. Performance Servo tests Yuken power amplifiers under simulated load against OEM specification, so you’re addressing the actual failure rather than replacing a unit that was never the problem.
If your Yuken power amplifier is showing erratic output or intermittent faults after basic troubleshooting, Performance Servo can bench-test the amplifier and confirm whether it’s the electronics, the valve, or the wiring causing the issue.