Ultrasonic cleaner but a bit faulty.

[diif]

After a not very cool noise and the display dimming my ultrasonic cleaner powered off. The display and fan work, just nothing happens when I press the ultrasonic button.
I think it's at least the triac that is at fault (on the small PCB), showing 57 ohms between pin 1 and 3 and possibly one of the relays (marked in red), I was hoping someone might advise. Thank you.

[R_J]

Re: Ultrasonic cleaner but a bit faulty.

The 57Ω might just be the gate resistance, It looks like the cleaner uses two seperate outputs to drive the transducers, I would think you could disconnect it to eliminate it as the problem.
What is wrong with the relay? the line marked in red is likely the normally closed position (will check shorted). It looks like the relay is there to short out the two diodes, Likely to run the second output module it supplies at half power when the diodes are in circuit, then full power when the diodes are shorted by the relay contacts.

Both fuses seem to be ok, I would check the 4 output transistors but I suspect if they were bad the fuses would be open.

[diif]

Re: Ultrasonic cleaner but a bit faulty.

Thanks R_J, yes, I suspected the relay as the diodes showed as short, but if that's as designed, it's ok. The fuses are ok, no shorts on the transistors, the only other thing I found strange was the 57Ω between pin 1 and 3 on the BTA41600B but you think that's also ok.

[R_J]

Re: Ultrasonic cleaner but a bit faulty.

The gate resistance is likely ok, I would expect if it was bad it would be shorted T1 ~ T2 (1 ~ 2) Is this resistance in or out of circuit?
That small board is connected to the mainboard (CN1?) which seems to control the a/c voltage to the second output module

[diif]

Re: Ultrasonic cleaner but a bit faulty.

Yes, measured out of circuit and yes the small board connects to CN1 and the 330k pot on the front controlling the power.

[CapLeaker]

Re: Ultrasonic cleaner but a bit faulty.

measure the resistors. They may look good, but yet out of spec. Big or small resistors, doesn't make a difference with this Chinese stuff... at least that is what I learned.

[R_J]

Re: Ultrasonic cleaner but a bit faulty.

There are a couple of components mounted to the bottom of the tub (red & white wires) it seems to connect between neutral & the PTC connection
The white plug with the 5 wires is +5v, ground, and the 3 relay coils via resistors. the other ends of the relay coils go to (-)
Maybe the microprocessor got confused?

[diif]

Re: Ultrasonic cleaner but a bit faulty.

Thanks CapLeaker, I checked a few but i shall check the rest in good light tomorrow.

Yes R_J the twin red and white wires go to a pair of PTC heating elements held on with aluminium tape. Tiny things for such a large tank, I don't use the heater.

The bbzzeert noise when the display dimmed came from one of the bottom boards rather than from the display board that has the micro on it.

[R_J]

Re: Ultrasonic cleaner but a bit faulty.

How does the bottom of the second output module look? no burnt connections? It could be a bad transducer, but it sounds like something arced