Cheap ultrasonic cleaner doesn’t work anymore

[caphair]

Powers on shows a display and lets you set a duration. When I press Start I can hear a relay click and the timer counts down but it never really starts. Not sure if it's fixable or worth it but figured I'd post. Maybe someone has experience with these.

[R_J]

Re: Cheap ultrasonic cleaner doesn't work anymore

Pull the board and look at the other side, there is likely an outout transistor that could be bad, or mybe just a poor connection.

[caphair]

Re: Cheap ultrasonic cleaner doesn't work anymore

Pull the board and look at the other side, there is likely an outout transistor that could be bad, or mybe just a poor connection.

I'll do that when I have a chance tomorrow. At the two terminals going to the bowl? I measure briefly around 115vac before it drops. In dc I measure around 35vdc. If that's a clue to anything. Do these work off ac at the output?

[R_J]

Re: Cheap ultrasonic cleaner doesn't work anymore

The output should be high frequency ac (42khz). Also Have a look at the piezo transducer (mounted to bowl) and see if it is cracked or broken
It is a switching power supply, U1 likely drives the two fets that drive the transformer, and the secondary of the transformer drives the piezo

[caphair]

Re: Cheap ultrasonic cleaner doesn't work anymore

I don't see any visible cracks on the piezo transducer. Also the two mosfets seem to measure good in circuit, diode readings in one direction.

[R_J]

Re: Cheap ultrasonic cleaner doesn't work anymore

Check the voltage across C10, it should be at least 150vdc), then use C10 - as ground and check the voltage on the 10k/2w resistor lead (next to C12). If you have voltage on C10 and not the resistor next to C12, check the solder connections on the relay, or the relay contacts could be bad.
Do you have VCC on the ic? or across C14?

[caphair]

Re: Cheap ultrasonic cleaner doesn't work anymore

Check the voltage across C10, it should be at least 150vdc), then use C10 - as ground and check the voltage on the 10k/2w resistor lead (next to C12). If you have voltage on C10 and not the resistor next to C12, check the solder connections on the relay, or the relay contacts could be bad.
Do you have VCC on the ic? or across C14?

By ic you mean U1? Also I'm not seeing C14 anywhere do you mean c15?

[R_J]

Re: Cheap ultrasonic cleaner doesn't work anymore

C15 is the small disc cap, next to it is C14 (partly covered by the screw) U1 is the only ic,

[caphair]

Re: Cheap ultrasonic cleaner doesn't work anymore

Check the voltage across C10, it should be at least 150vdc), then use C10 - as ground and check the voltage on the 10k/2w resistor lead (next to C12). If you have voltage on C10 and not the resistor next to C12, check the solder connections on the relay, or the relay contacts could be bad.
Do you have VCC on the ic? or across C14?

C10 = 316vdc when “start” pressed and 328vdc when in standby
Same readings on R3 next to c12

C14 and Vcc of u1 = 13vdc when “start” pressed

[R_J]

Re: Cheap ultrasonic cleaner doesn't work anymore

That all seems correct, you have 316v for the the fets, and 13vdc VCC for the ic, You could check the voltage between U1 pin 4 (common) and 5 (VS) should be quite high around 150vdc. If its 0 or 316v the ic could be bad.
Then I would check that the transformer is not open. I took a guess as to how it should be configured.(see picture)
The actual output circuit is very simple, U1 has High and low outputs to drive the two fets at 42khz, the two fets switch the 316vdc to output a 42khz signal to the piezo. The transformer provides a small sample of that signal to the CT pin of the U1 If that signal is missing the IC wil shut down.

If you have the ic's datasheet, you will see 4 internal fets, you should be able to check that they are not shorted D~S
IE: from pin 7 to pin 6 and pin 7 to pin 8 should be open.

[caphair]

Re: Cheap ultrasonic cleaner doesn't work anymore

Found Datasheet and pins 6 and 7 measure .043 in diode mode both ways and slowly increase, but sometimes they measure .565v one way and OL the other.

Vs pin 6 measures 28v

[R_J]

Re: Cheap ultrasonic cleaner doesn't work anymore

Did you check the transformer?

[caphair]

Re: Cheap ultrasonic cleaner doesn't work anymore

Did you check the transformer?

No I actually forgot to because I thought the 28v on Vs meant the ic itself was bad. I’ll check it tomorrow. Do I just measure ohms across the three windings you drew up?

[CRT Informatica]

Re: Cheap ultrasonic cleaner doesn't work anymore

ola

[caphair]

Re: Cheap ultrasonic cleaner doesn't work anymore

Did you check the transformer?

Here are the values I get on the transformer. Shown in the picture I've attached

[R_J]

Re: Cheap ultrasonic cleaner doesn't work anymore

It looks like the transformer is just there to provide feedback to the ic. If you have a scope (and isolation xfmr) to check the ic outputs, the circuit is very simple so if the fets are ok, the transformer seems ok, you have the voltages, HV for the output fets and VCC for the ic, maybe check that C16 (across the output to the piezo) is not shorted, it does'nt leave much.
I would try a new ic

[caphair]

Re: Cheap ultrasonic cleaner doesn't work anymore

It looks like the transformer is just there to provide feedback to the ic. If you have a scope (and isolation xfmr) to check the ic outputs, the circuit is very simple so if the fets are ok, the transformer seems ok, you have the voltages, HV for the output fets and VCC for the ic, I would try a new ic

The transformer isn’t stepping up the voltages at all? I don’t have a scope unfortunately. Should I just try another ic? This one is labeled IR2153 and I found replacements but it’s labeled IR2153S. Think it’ll be a suitable replacement?

[stj]

Re: Cheap ultrasonic cleaner doesn't work anymore

the large transformer has fractured solder joints.

[R_J]

Re: Cheap ultrasonic cleaner doesn't work anymore

The transformer isn’t stepping up the voltages at all? I don’t have a scope unfortunately. Should I just try another ic? This one is labeled IR2153 and I found replacements but it’s labeled IR2153S. Think it’ll be a suitable replacement?

The transformer is not to step up the voltage but just to provide a stepped DOWN sample voltage to control the ic.
The IR2153S is just an improved version of the ic

[caphair]

Re: Cheap ultrasonic cleaner doesn't work anymore

Alright I guess I’ll just try another ic. Cheap enough