A Parker drive going down rarely gives you much warning. One shift it is running fine, the next you have a fault code on the display, a stopped line, and a maintenance team trying to figure out whether to reset it, call a repair shop, or start hunting for a replacement. If the machine is ten or fifteen years old, that last option gets complicated fast — Parker SSD drives are not always sitting on a distributor's shelf.
This guide covers the Parker drive families we see most in the workshop — the 690+ AC drive, the 590 DC drive, and the Compax3 servo drive — what causes them to fail, what the fault codes actually mean, and how to decide whether repair or replacement makes more sense for your situation.
The Parker Drive Families Worth Knowing
Parker Hannifin has produced several generations of drives under the SSD brand. Each family has its own failure patterns, its own quirks, and its own level of parts availability in 2025.
Parker 690+ — The Workhorse AC Drive
The 690+ is a flux vector AC drive covering 0.75 kW to 400 kW. It has been installed in extruders, paper machines, winding systems, mixers, and compressors across every industry. Robust, flexible, and built for continuous duty — but many units in service today are pushing 15–20 years old. At that age, you are in the window where DC bus capacitors, IGBT modules, and internal power supplies all start to fail on statistical schedule.
The 690+ supports a broad range of communication options — PROFIBUS, DeviceNet, CANopen, Modbus — and its parameter structure is well-documented. When one fails, it is almost always repairable. The control board is usually fine; the failure is in the power stage or the internal PSU.
Parker 590 — The DC Drive That Refuses to Die
The 590 is a 4-quadrant DC drive, available from 15 A to 1850 A. It is the standard solution for keeping older DC motor machines running rather than converting them to AC — and there are a lot of those machines still in service. The 590 uses thyristors (SCRs) rather than IGBTs, which makes it a different repair discipline. Thyristor failures are often caused by commutation problems, misfires from noisy firing circuits, or simply age and thermal cycling over decades of service.
Replacement drives for the 590 are increasingly difficult to source new. Repair is almost always the right answer here.
Parker Compax3 — The Precision Servo Drive
The Compax3 is Parker's digital servo drive for high-precision motion — positioning, force control, synchronization. It runs rotary and linear motors, programs in IEC 61131-3 via C3 ServoManager, and handles coordinated multi-axis profiles. You find it in welding machines, CNC systems, assembly automation, and test equipment.
The Compax3 is more sensitive than a general-purpose AC drive. Its encoder interface circuits are exposed to induced voltages from long signal cables. Its flash memory can be corrupted by line transients. When a Compax3 goes down, the machine stops completely — there is no manual fallback.
Parker Aries and Gemini — Legacy Servo Drives Still Running
The Aries (AR-xx) and Gemini (GV, GT series) servo drives were discontinued but are still running in a large number of machines built in the 2000s and early 2010s. New replacements are hard to find. If one fails, your options are repair, a tested reconditioned unit, or a costly machine retrofit. We keep stock of tested Aries and Gemini units precisely for this reason.
Parker 690+ Fault Code Reference
The 690+ uses a two-letter fault code system displayed on the keypad. Here are the codes we see most often in the field:
| Fault Code | Name | Most Likely Cause |
|---|---|---|
| OV | DC Bus Overvoltage | Deceleration ramp too fast, no braking resistor, or regenerative load — check ramp time first. If fault occurs at idle, suspect aging DC bus capacitors. |
| UV | DC Bus Undervoltage | Mains supply below threshold, blown input fuse, or failed inrush/precharge circuit. Check supply voltage and all fuses before suspecting the drive. |
| OC | Overcurrent | Output short circuit, ground fault on motor cable, or failed IGBT module. Do not keep resetting OC faults — each reset risks further damage to the power stage. |
| OT | Over Temperature | Heatsink too hot — check cooling fan is running, heatsink fins are not blocked, and ambient temperature is within spec. Also check if drive is undersized for the load. |
| EF | Earth/Ground Fault | Leakage current detected on output. Isolate motor and cable and test insulation resistance. If fault clears without motor connected, the motor winding insulation is degraded. |
| PS | Power Stage Fault | Internal hardware fault in the power module or gate driver. This fault requires bench diagnostics — do not attempt repeated resets. |
| CL | Current Limit | Drive hit the current limit continuously — motor overloaded, mechanical binding, or incorrectly set current limit parameter. |
| SP | Overspeed | Motor exceeded the overspeed threshold — check maximum speed parameter, encoder signal integrity, or runaway condition in closed-loop mode. |
| PH | Phase Loss | One input phase missing or severely unbalanced. Check incoming supply, contactor operation, and input fuses individually per phase. |
| CRC | Parameter Checksum Error | Parameter memory corrupted — usually after a power transient. Factory reset required. Back up parameters before and after any firmware work. |
Why Parker 690+ Drives Fail — What We Actually See
DC Bus Capacitor Aging
This is the number one failure mode on drives that are more than 10 years old — and it is entirely predictable. The electrolytic capacitors on the DC bus have a finite lifespan, typically 8–12 years depending on operating temperature and load cycling. As they age, capacitance drops and equivalent series resistance (ESR) rises. The drive starts showing symptoms before the capacitors fully fail: longer charge times, OV faults during deceleration that were never a problem before, random shutdowns under full load.
Drives that have been sitting idle for a year or more are particularly at risk. Electrolytic capacitors degrade faster without regular use. A drive that has been on a shelf for two years may appear dead when first powered up — the capacitors have de-formed and the inrush current trips the protection circuit before the bus even charges.
The fix is straightforward: measure ESR and capacitance on every capacitor, replace everything out of specification with 105°C industrial equivalents, and reform idle drives on a variable voltage controller before applying full power. We do this on every 690+ we receive that is over eight years old, regardless of the reported fault.
IGBT Module Failure
The IGBT modules in the 690+ are the core of the power conversion — they switch hundreds of volts at high frequency to synthesize the AC output waveform. IGBT failure is usually sudden and obvious: blown fuses, a burnt smell, sometimes visible damage on the module. Causes include output short circuits, ground faults on the motor cable, fast deceleration without a braking resistor, and line voltage spikes from nearby large loads switching on the same supply.
The damage from a single hard short circuit is usually limited to the power stage. The control board and gate driver survive in most cases. That means the repair cost is a fraction of replacement — you are replacing one module, not the whole drive.
Internal Power Supply Failure
Every 690+ has an internal switched-mode power supply feeding the control board, gate drivers, and cooling fan. When this fails, the drive goes completely dark — no display, no fan, no response to anything. It is consistently misdiagnosed as a dead control board. The actual fault is almost always a failed primary-side MOSFET or a burned startup resistor in the SMPS. The control board itself is fine. This is one of the least expensive repairs we do on the 690+ series.
Cooling Fan Bearing Failure
690+ drives above about 2.2 kW use internal cooling fans. As the fan bearing ages, airflow drops and the heatsink runs hotter than it should. The drive begins thermal limiting — reducing output current to protect itself — before eventually tripping on OT. The pattern is distinctive: runs fine for the first 30–60 minutes of a shift, then slows down or faults as it heats up. Replace the fan and the problem goes away.
Parker Compax3 — What Goes Wrong
The Compax3 fails differently from a general-purpose drive. The power stage is less likely to be the problem — the encoder interface and control electronics are the weak points.
Encoder interface damage is the most common Compax3 fault we see. Long encoder cables running parallel to power cables pick up induced voltages, especially in poorly shielded installations. A single spike on the encoder lines can destroy the receiver IC on the servo drive's control board. The symptom is a following error or encoder feedback alarm that does not clear regardless of how the encoder is wired.
Corrupted parameter flash happens after line transients or an interrupted firmware update. The Compax3 boots into a fault state and C3 ServoManager cannot connect properly. Recovery requires reflashing the firmware and restoring the parameter set from backup — or reconstructing the parameters if no backup exists.
Internal PSU failure produces the same "completely dead" presentation as the 690+. No LED activity, no communication response, nothing. Same repair approach: isolate and repair the internal power supply at component level.
Repair vs. Replace — The Practical Decision
The math on repair vs. replacement has shifted significantly in recent years. A new Parker 690+ in the mid-to-high power range costs $3,000–$15,000 depending on frame size. Lead times from distributors for less common ratings can run 8–16 weeks. A component-level repair typically costs 20–35% of the new drive price and takes 5–10 business days.
For the 590 DC drive and legacy servo drives like the Aries and Gemini, new replacement is often not a realistic option at all — either the product is discontinued or the lead time makes it impractical for a production machine that needs to run. Repair or a tested reconditioned unit is almost always the right answer.
The one scenario where replacement clearly wins: a drive that has suffered catastrophic damage — submerged in water, burned through from a sustained short circuit, physically destroyed. Everything else is usually repairable.
Parker Drives — Supply and Repair at Flexa Systems
Flexa Systems is an exclusive Parker Hannifin supplier. Every product in the Parker automation catalog — 690+, 590, 650/660, Compax3, Aries, Gemini, ACR motion controllers, communication modules, and accessories — is available either from stock or to order. If a part number is not on the shelf, we source it directly and confirm pricing and availability within 4 business hours.
We also carry tested reconditioned Parker units for the most common references — useful when you need something running today and cannot wait for a new drive to arrive.
On the repair side, we work at component level across the full Parker range. No board swaps, no guesswork — we find the failed component, replace it with an industrial-grade equivalent, test under real motor load, and ship back with a 2-year warranty.
Full details on the Parker products we supply and the repair service are on our Parker Drives page.
Frequently Asked Questions
My Parker 690+ trips OV fault only during fast deceleration — is the drive faulty or is it a parameter issue?
Start with the parameter. Increase the deceleration ramp time (parameter A3 or equivalent depending on firmware version) and see if the fault clears. If the machine cannot tolerate a longer ramp, you need a braking resistor sized for the regenerated energy. If OV occurs even with a slow ramp and a braking resistor in place, then the DC bus capacitors are likely aging and need ESR testing. Send it in if that is the case.
My Parker Compax3 is completely dead after a power cut — no LEDs, no communication. Is it repairable?
In most cases, yes. A Compax3 that goes completely dark after a power event has almost always lost its internal power supply — not the control processor. This is a component-level repair, not a board replacement. Send us the catalog number and we will give you a quote.
I need a Parker Aries servo drive urgently — I cannot find one anywhere. Can you help?
Yes. We keep tested Aries units in stock for exactly this reason. Contact us with the part number and we will confirm availability. If we do not have your exact model, we can usually repair your faulty unit on a priority basis or source a compatible reconditioned unit.
Can you repair a Parker 590 DC drive?
Yes. We repair the 590 series at component level — thyristor modules, firing circuit boards, internal power supplies, and control boards. The 590 is a robust machine and most faults are repairable. Send us the catalog number, the current rating, and a description of the fault.
Do parameters get preserved after repair?
Yes — unless the fault specifically involves corrupted parameter memory, we do not reset the drive. Your parameters come back intact. If a reset is unavoidable (e.g., corrupted flash on a Compax3), we let you know before proceeding so you can check whether you have a backup.
Get a Quote or Send Your Drive In
Whether you need a new Parker drive, a tested reconditioned unit, or a component-level repair with a warranty — visit our Parker Drives page for the full product and repair overview, or request a quote directly with your catalog number and fault description. We respond within 4 business hours.