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Old 19th October 2012, 09:35 PM   #1
Yooper is offline Yooper  United States
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Join Date: Oct 2012
Location: Da UP
Default Blown parallel FETs?

If you ever had a bank of FETs fail, you know the feeling.

Here's a handy way of finding the bad one.
Note: not plural.

Put an ohmmeter across D - S.
Take a large soldering iron and hold the tip on the body of the each FET and heat it up.

If it's the bad one, the ohm reading will noticeably increase.

Beats the heck out of desoldering, especially if SMT devices.
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Old 20th October 2012, 11:14 AM   #2
AndrewT is offline AndrewT  Scotland
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Join Date: Jul 2004
Location: Scottish Borders
are you referring to vertical Power mosFETs?
regards Andrew T.
Sent from my desktop computer using a keyboard
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Old 20th October 2012, 06:04 PM   #3
sbrads is offline sbrads  United Kingdom
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Join Date: Jun 2005
Location: Kent, UK
That trick works for most zapped semiconductors in parallel with whatever, although sometimes a few more volts are needed than whatever a typical DVM delivers on the ohms or diode range.
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Old 21st October 2012, 12:06 AM   #4
diyAudio Member
Join Date: Feb 2010
I used to have a 4volt 400va transformer with 2x56000uF caps.
needed safety glasses, but it could find and fix any short circuit.
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