Author Topic: Searching for a specific component with little informations  (Read 150 times)

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Offline theredcat

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Searching for a specific component with little informations
« on: April 26, 2020, 08:13:48 pm »
Hi, Looong time EEV follower, but this is my first post :)

I'm searching for a specific component for a Techtronic Industries (parent company for ryobi, AEG, Milwaukee, and others) board that is in my power grinder (BEWS18-125X)

It just bursted into flame and I can't identify the specific model since the serial number is more or less calcined

The only clues that I have are :
  • It's a perfectly squarre TO220 package (no small "dents" on the sides)
  • Probably a power transistor since the board have the label Q6 for that component
  • The part number on the first line start with IR and ends with 7
  • The second line starts with a capital "i"
  • There is the letters "FMCW" on the last line

I'm not much convinced that someone will have the answer, but if you do, you'll save me ~35€ for the complete board :)

Offline bob91343

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Re: Searching for a specific component with little informations
« Reply #1 on: April 26, 2020, 10:11:53 pm »
It's probably an FET.  Many of those have part numbers from International Rectifier and start with IRF.  I have a few that might work in your circuit but they are cheap and readily available.

Offline TheMG

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Re: Searching for a specific component with little informations
« Reply #2 on: April 27, 2020, 12:07:21 am »
More than likely an N-channel MOSFET, probably "logic level" meaning the Vgs threshold voltage is low enough it can be fully switched on from the 3.3 or 5V output of a typical microcontroller (hint: look for the presence or absence of a voltage regulator on the board).

Some amount of circuit analysis will be needed to determine if this is in fact the case.

Most important characteristics for picking the right part will be:

Vgs(th) - must be low enough to allow the driving circuitry to switch the transistor fully on, but not so low as to exceed the maximum gate voltage
Vds(max) - you probably want to be some margin higher than the maximum fully charged battery voltage, but don't go too crazy on this one, higher is not always better, as MOSFETs with higher voltage ratings tend to have higher on resistance as well as lower current handling
Id(max) - this is the tricky one, because you don't know and there is no easy way to determine the peak current that will pass through the MOSFET, so you'll just have to go with the highest rated one (within reason) that also meets the above criteria.

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