When Does a PMU Device Need Servicing? 8 Warning Signs You Shouldn’t Ignore

A PMU device may still switch on, display the correct frequency and move the needle, yet no longer perform in the same way it did before.

The change often begins subtly: the sound becomes more metallic, additional vibration can be felt in the hand, the device responds differently to the cartridge, or its operation seems less smooth. Because the deterioration occurs gradually, the artist becomes accustomed to the device’s new behaviour and begins compensating for it with their hand.

This is the point at which a technical issue can begin to affect technique.

Not every unusual sound indicates a malfunction, and not every change requires repair. Cartridges differ in membrane resistance, guide friction and the mass of their moving components. A proper assessment should therefore be based on comparing the device under controlled conditions rather than on guesswork.

A PMU device is an electromechanical system

Inside the device, the motor’s rotary motion is converted into the reciprocating motion of the needle. This process involves, among other components, the drive mechanism, bearings, push rod, guiding elements, cartridge, electronics and control software.

A brushless motor eliminates wear associated with brushes and a commutator, but it does not make the entire device indestructible. Micromotor manufacturer FAULHABER states that the service life of brushless motors is generally limited primarily by ball-bearing wear, while the lifespan of the entire system is also influenced by factors such as load, operating conditions and duty cycle. FAULHABER – Motors Support

In practical terms, this means something simple: a professional device can be durable and serviceable, but it still performs tens of thousands of cycles during a single procedure. Mechanical components remain in motion, surfaces interact with one another, and an impact or fall can alter their alignment without leaving any visible damage to the housing.

1. The sound of the device has noticeably changed

Every device has its own acoustic characteristics. The fact that one machine sounds different from another does not, by itself, indicate a fault. What matters is a change compared with the previous operation of the same device under the same conditions.

Possible diagnostic warning signs include:

• a new metallic tone,

• cyclical knocking or rattling,

• a sound that changes in rhythm with the device’s operation,

• a clear difference between operation without a cartridge and operation with a properly fitted, verified cartridge,

• a sudden increase in volume at the same frequency.

Sound is affected by speed, load, the way the motor is mounted and the bearing system. A single test with one cartridge is therefore not sufficient. Begin by fitting a new cartridge from a batch with known performance. If the sound remains, the device should be submitted for technical diagnostics.

2. The device vibrates more than it did before

A certain level of vibration is natural in a device that performs cyclical motion. What should raise concern is a change: vibration that was not present before, that becomes progressively stronger, or that increases noticeably within a specific frequency range.

Possible causes include wear of a guiding component, excessive play, incorrect seating of a drive component, damage caused by a fall, or a cartridge with unusually high resistance. The source cannot be identified reliably without inspecting the internal mechanism.

In mechanical engineering, changes in vibration levels are used as one of the parameters for monitoring the condition of rotating machinery. The ISO 20816 series is not intended for handheld PMU devices, and its numerical limits must not be applied to them. It does, however, support the general diagnostic principle that a significant change in vibration compared with normal operating conditions requires investigation. ISO 20816-1

3. The device runs inconsistently at a familiar setting

Artists are most likely to notice a change when using parameters they work with regularly. If the device intermittently speeds up, slows down, pulses or appears to cut out at the same setting, the first step is to determine whether the issue comes from the device or the cartridge.

Perform three short comparison tests:

1. Insert a fully charged battery known to be working correctly.

2. Fit a new cartridge of a type whose behaviour you already know.

3. Test several frequencies without skin contact and then on practice latex.

If the irregular operation occurs with only one cartridge, the cartridge is the most likely source of the problem. If the issue repeats with several verified cartridges and batteries, the device requires technical assessment.

4. The device stops or becomes noticeably weaker under load

A cartridge introduces membrane resistance, guide friction and the mass of moving components into the system. A properly functioning device should operate within the range of loads specified by the manufacturer, but not every cartridge places the same load on the mechanism.

If the machine begins to stop, slows down noticeably or cannot start smoothly with a correctly fitted cartridge, do not automatically increase the frequency or press the device harder against the skin. Replace the cartridge first. If the symptom repeats, stop using the device and contact the service department.

Compensating for a fault by changing the settings may temporarily conceal the symptom, but it will not eliminate its cause.

5. The needle movement no longer appears axial or excessive play has developed

The needle should move along the cartridge’s guiding axis. Visible lateral movement may originate from the cartridge itself, its internal guidance system or incorrect seating. If it occurs with multiple correctly functioning cartridges, the source may also be a component of the drive mechanism or the grip.

Do not attempt to straighten, press or adjust components of the mechanism yourself. A precision system operates within defined tolerances, and an adjustment performed “by eye” can increase friction or transfer the problem to another part of the mechanism.

6. The housing becomes warmer than usual

The motor, electronics and battery generate heat during operation. A slight and stable increase in temperature does not necessarily indicate a fault. What is abnormal is a device that suddenly becomes noticeably warmer than it did during previous sessions of a similar duration and at similar settings.

An increase in temperature may accompany higher friction, abnormal load, a battery issue or an electronic fault. If the housing becomes hot, there is a smell of overheating, smoke appears or the battery becomes deformed, switch the device off immediately. Remove the battery only if it is safe to do so, and do not switch the device on again before it has been assessed by the service department.

7. The problem appeared after a fall or strong impact

The absence of a dent does not mean that no damage has occurred. The energy of the impact can be transferred through the housing to the bearings, shaft, eccentric mechanism, electrical connections or guiding components.

After a fall, pay attention to:

• changes in sound,

• increased vibration,

• needle wobble or lateral movement,

• problems adjusting needle protrusion,

• unstable power delivery,

• damage to the thread or grip.

If the device has fallen from working height, a technical inspection is justified even if it still switches on. Continuing a procedure on a client should never be used as a test of whether the device is functioning correctly.

8. Liquid may have entered the device

Pigment, disinfectant or another liquid may enter the housing through the buttons, gaps, port or thread. Symptoms do not always appear immediately. Over time, contamination can affect electrical contacts, electronics and moving components.

Do not switch the device on “to see whether it still works,” and do not attempt to dry it using hot air. Remove the power source if the manufacturer’s design allows this and it is safe to do so, then contact the service department. Information about the type of liquid and where contact occurred will assist with the diagnostic process.

Cleaning, technical inspection, repair and upgrade are not the same

These terms are often used interchangeably, even though they describe different procedures.

Procedure	Purpose
External cleaning	Removing contamination from accessible surfaces in accordance with the manufacturer’s instructions
Technical inspection	Assessing the condition of the mechanical system, electronics, drive mechanism and wear components
Repair	Correcting a specific fault and restoring proper operation
Upgrade	Introducing a newer technical solution or function, if this option is offered by the manufacturer

An upgrade does not replace the diagnosis of a damaged motor, bearing or component affected by a fall. Similarly, cleaning the housing is not the same as inspecting the internal components of the device.

Should a PMU device undergo preventive servicing?

There is no single correct service interval for every device and every artist. Wear depends on the design, number of operating hours, frequencies used, cartridge loads, transportation, falls, contamination and storage conditions.

Manufacturers of professional rotary machines publish separate maintenance procedures, instructions and service pathways for individual models. This does not mean that one service interval applies to every PMU device. The appropriate schedule should be based on the manufacturer’s instructions, intensity of use and the history of the individual device.

Preventive inspection is particularly valuable when the device is the artist’s primary working tool, is used for multiple procedures every week, or has been dropped, transported in difficult conditions or exposed to liquid.

Basic diagnostics before contacting the service department

Before contacting technical support, prepare:

• the device’s serial number,

• a brief description of the symptom and when it occurs,

• information about whether the device has been dropped or exposed to liquid,

• the frequency and configuration used when the problem occurred,

• the type of cartridge used,

• the result of testing with a different new cartridge and another fully functional battery,

• a short recording of the sound or behaviour of the device.

Do not disassemble the housing, lubricate the mechanism with an unsuitable product or attempt to eliminate mechanical play yourself. Even official maintenance instructions for rotary machines state one clear principle: lubrication should only be performed when and in the manner specified by the manufacturer.

Which symptoms require you to stop working immediately?

Do not use the device on a client until it has been diagnosed if at least one of the following symptoms occurs:

• a smell of overheating, smoke or an abnormally hot housing,

• a damaged, deformed or excessively hot battery,

• liquid inside the housing,

• sudden and severe vibration,

• visible needle wobble occurring with several verified cartridges,

• the drive mechanism stopping,

• damage to the housing, thread or grip following a fall.

Having a second fully functioning machine in the studio is not a luxury. It protects the continuity of your work and prevents you from having to decide whether to complete a procedure using a device whose technical condition is uncertain.

FAQ

Does louder operation always indicate a damaged motor?

No. The sound can be affected by the cartridge, its membrane, guide friction, operating frequency or the way it has been fitted. However, if the change remains when several verified cartridges are used and represents a clear difference from how the same device operated previously, technical diagnostics are required.

Can I continue working if the device only vibrates slightly?

The natural level of vibration depends on the device’s construction. New or progressively increasing vibration should raise concern. If you notice a clear change, do not assess whether it is safe to continue working solely on the basis that the device still switches on.

Can replacing the cartridge solve the problem?

Yes, if the issue is caused by a defective cartridge or one with unusually high resistance. A new cartridge of a known type should therefore be the first component used in a comparison test.

Does a device with a brushless motor require servicing?

A brushless motor does not contain brushes that wear out, but the device still contains bearings, mechanism components, guiding elements, electronics and connections. “Brushless” does not mean “free from wear components.”

After a fall, is it enough to test the machine on latex?

A latex test may reveal an obvious problem, but it cannot confirm the condition of the bearings, alignment, connections or electronics. After a strong impact, a technical inspection is the correct assessment method.

Is upgrading the device the same as repairing it?

No. An upgrade introduces newer solutions offered by the manufacturer. A repair corrects a fault. The device should be assessed before an upgrade because a defective component may require separate replacement.

Conclusions

The technical condition of a PMU device is not binary. The equipment does not have to stop working completely for its behaviour to begin deviating from normal performance.

The most important point of reference is change: a new sound, increased vibration, a different operating temperature, irregular performance or a weaker response under load. The first step should be a controlled test using a fully charged battery and a known, verified cartridge. If the symptom repeats, the solution is not to apply more pressure or randomly change the settings, but to have the device professionally diagnosed.

Engineering before marketing also means taking responsibility after the purchase. A device should not only be well designed—it should also be possible to inspect, repair and maintain it properly throughout its entire service life.