Bringing an Vevor Ultrasonic Cleaner Back from the Dead

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I recently repaired an ultrasonic cleaner - the control board and timers functioned, the cooling fan function, the water heaters functioned, however, when selected - no ultrasonic action.

Immediate suspicion - ultrasonic drive board, or a broken / disconnected wire within the unit.

I'm not an electronics repair expert - Chat GPT - particularly it's ability to examine photos assisted with the diagnosis. 

Initial Symptoms

  • Control logic powered normally

  • Ultrasonic function could be toggled

  • Cooling fan ran, but slowed when ultrasonic load requested

  • No ultrasonic action

No blown fuses. No disconnected wires. No obvious shorts. First step was to remove the ultrasonic driver board and give it a good lookover. 


The ultrasonic driver board is pretty simple - single layer circuit board, lots of space on the board, components are identified and the circuit is easy to trace. 

Output Stage: Failed Transistors

Early checks pointed to the two output transistors (VO1 and VO2). Once removed, both tested faulty (using the diode function on a multimeter). They were replaced with upgraded, first tier equivalents.

Post-installation checks showed no hard shorts and reasonable collector–emitter resistance (~27 kΩ in-circuit), but ultrasonic output was still absent.

So - continue looking for additional faults. 

A Visibly Damaged Resistor


Further inspection revealed a resistor in the output/transformer path that was visually compromised. Discoloration and surface damage were obvious, and out-of-circuit testing confirmed it had failed open. Once removed from the board you could see the crack in the shell. 

The resistor decoded to 5.1 Ω and was replaced with a flameproof part with double the current rating - physically larger, with thicker leads. Interstingly, the leads fit the original holes in the board. With lots of space between components, it was easy to fit the larger resistor in place.

Functional test - still no ultrasonic action.

Following the Heat

At this point, the board was re-examined for additional problems. A closer look on the trace side of the board showed a diode solder joint that had clearly reflowed from heat, not from poor assembly.


That diode was D6, feeding one output transistor. Its counterpart on the parallel path was D5.

D5 and D6: Quiet Failure

D5 and D6 were fast-recovery diodes (FR157 class). In-circuit measurements were misleading; out-of-circuit testing showed abnormal behavior - failed diode tests.


Both were replaced with UF5408 ultrafast diodes, with double the current rating. They were physically larger, but the leads fit the board perfectly and offered significantly more thermal and current margin.



Sanity Checks and Power-Up

Before power-up:

  • VO1/VO2 collector–emitter measured normal

  • Output-to-neutral measured OL (proper isolation)

  • Output-to-output measured ~1.1 Ω, consistent with transformer winding resistance

With everything reconnected, power was applied.

Ultrasonic action immediately returned.

What Failed — and Why

This was a multi-stage, heat-driven failure:

  • Fast diodes degraded quietly

  • Excess stress propagated into the output transistors

  • A series resistor failed open

  • Heat left physical evidence in the form of reflowed solder

Final Notes

The ultrasonic board is back in service. I've built a small stash of electronics parts for future repairs. We'll see how long the repair lasts. If I get that thermal camera from Santa this Christmas - I'll go back and check out this board in operation to see how hot the board is running. 

On to the next problem.

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