Vatech Ez3D / Vex S300W: Intermittent failure to fire high voltage despite ready indication
What happened
As reported in the case, roughly once every two weeks or more often the unit fails to apply high voltage during exposure, while the exposure button shows green (ready). No error codes were displayed.
What was checked
- Confirm the pattern first: ready indication green, no high voltage on exposure, no error codes, recurring roughly every two weeks or more often (as reported in the case).
- Flex-test the high-voltage cable run through the arm elbow through its full travel with the unit isolated: an intermittent fault may show no visible break at all.
- Note the service history: in this case the wires had already been replaced earlier, so a past repair is not proof of a healthy harness.
- Generator diagnostics were run by the manufacturer's authorised service and pointed at the generator, so cross-check the cable path before accepting that conclusion.
- The engineers proved the wiring fault by routing a temporary test cable line directly over the elbow — strictly a diagnostic check, not a repair.
Cause
Probable cause in this case: fatigue damage of the high-voltage wires where they flex in the arm elbow — intermittent, not necessarily visible as a clean break. Engineers familiar with this model reported the same symptom on other units, so it may be a known weak point, but this note reflects a single case.
The cause is probable and was not fully confirmed.
What was done
The recommended fix was replacement of the cables with high-flex high-voltage ones or fitting a complete elbow assembly ordered through authorised channels; the case reported a lead time of three to six months. The directly routed line over the elbow was used only to verify the diagnosis and must be removed before the unit goes back into use.
Safety
High-voltage cables and the generator can hold a lethal stored charge, and this is a radiation-producing device: isolate the unit and discharge per the manufacturer's procedure before touching any HV wiring, and complete electrical safety and radiation output checks before returning it to clinical use.
Lesson: A green ready light proves the control loop, not the power path — with intermittent exposure faults, stress-test the moving high-voltage harness at flex joints before condemning the generator.
Covered in the course: Dental Equipment Service — Level 2: Fault-Finding →
Written from an anonymised case shared by service engineers. It is not a manufacturer instruction and grants no authorisation. Independent note; names are trademarks of their owners.