Electronics > Repair

ultrasonic cleaner MH-060S, replacing transistors [fixed > broken again]

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wraper:

--- Quote from: htm on August 09, 2024, 07:46:14 pm ---@fzabkar
Afaik, the C3320 has pin layout: 1(B) 2(C) 3(E)
The diode tests show:

BC
black on 1, red on 2 = OL
red on 1, black on 2= OL

CE
red on 2, black on 3 = OL
black on 2, red on 3 = 0.488V

BE
red on 1, black on 3 = OL
black on 1, red on 3 = OL

--- End quote ---
It's an N-channel MOSFET, what you're measuring between pins 2 and 3 is an intrinsic body diode. Tester detects is as a diode probably due to high gate-source threshold voltage.

htm:
@wraper
I tested it. Indeed!
The MOSFET is changing from Off to On from 4.1V to 5V.

But why didn't the Component tester see it as a MOSFET? aren't most mosfets switching in that area

wraper:

--- Quote from: htm on August 09, 2024, 10:09:14 pm ---@wraper
I tested it. Indeed!
The MOSFET is changing from Off to On from 4.1V to 5V.

But why didn't the Component tester see it as a MOSFET? aren't most mosfets switching in that area

--- End quote ---
Most modern ones have lower VGS(TH). Your tester probably cannot supply enough voltage or measure above some value below it. Or maybe its firmware has some quirks. I wouldn't outright trust what such testers automatically detect.

htm:
Today i finished replacing the defective diodes and the 4 transistors.
On both boards 1 transistor seemed ok, but i replaced those as well, just in case. I rather have them all be the beefy BUV48A :D

Did a testrun of a minute, and..  :phew: :-+ 

Thanks for all advice!

htm:
 :palm: .. he used it about 3 times, and then it quit on him again.

i'll take another look at it, to see if the same thing happened again.

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