240 and 9240 can they be checked with DVM? - diyAudio
Go Back   Home > Forums > Amplifiers > Pass Labs

Pass Labs This forum is dedicated to Pass Labs discussion.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 30th May 2011, 04:32 AM   #1
semi932 is offline semi932  United States
diyAudio Member
 
semi932's Avatar
 
Join Date: Nov 2009
Default 240 and 9240 can they be checked with DVM?

Think I got some bad irfp 240's and 9240's.
Just for experiment I used diode function and measured from Source to G and D.
On some I get about .450v give or take for brevity.

Others I get one measurement and OL from S to G.
These I think are bad.

Does this make any sense or am I grasping for straws?
  Reply With Quote
Old 30th May 2011, 01:47 PM   #2
Marra is offline Marra  United Kingdom
diyAudio Member
 
Join Date: Nov 2009
Location: Near Lincoln
Hope this is helpful :- MOSFET testing
  Reply With Quote
Old 31st May 2011, 09:33 AM   #3
h_a is offline h_a  Europe
diyAudio Member
 
h_a's Avatar
 
Join Date: Sep 2006
Location: Graz, Austria
From above link

Quote:
On most multimeters (but by no means all!) this puts about 3-4v across the device under test.
I doubt any quality meter will do that. Even if it did, turn-on voltage of the P-channels goes up to 4.5 V, so outside this range.

You can only check wether the gate is shot by measuring resistance from gate to source (or drain), it should be a large number like Megaohms or similar.

Otherwise there is not much reasonable way to test them (to my knowledge at least) without building a little circuit around the fets to measure drain-current, gate-voltage and, ideally, gate leakage current.

Hannes
  Reply With Quote
Old 31st May 2011, 09:12 PM   #4
semi932 is offline semi932  United States
diyAudio Member
 
semi932's Avatar
 
Join Date: Nov 2009
Thanks but got some direction on another forum.
I'll link to it so all can see whether it suits them.

Can hexfets be checked with a dvm? - AudioKarma.org Home Audio Stereo Discussion Forums
  Reply With Quote
Old 31st May 2011, 09:25 PM   #5
diyAudio Member
 
nigelwright7557's Avatar
 
Join Date: Apr 2008
Location: Carlisle, England
In my experience of many faulty mosfets they been short D-S.
I had only one that was short G-S.
__________________
PCBCAD50 software. http://www.murtonpikesystems.co.uk
  Reply With Quote
Old 31st May 2011, 10:00 PM   #6
flg is offline flg  United States
diyAudio Member
 
flg's Avatar
 
Join Date: Jul 2005
Location: North East
Yes, Nigelwright has a point I agree with. However, excluding the occasional short cuirict insident, blowing the G-S oxide (ussually greater than 15-20V) is easy in an ESD rich atmosphere like the carpeted area of your house
That would make the G-S low resistance but maybe at somewhat higher voltage than the ohm-meter uses.
__________________
"It was the perfect high end audio product: Exotic, inefficient, expensive, unavailable, and toxic." N.P.

Last edited by flg; 31st May 2011 at 10:09 PM.
  Reply With Quote
Old 1st June 2011, 04:45 AM   #7
Blues is offline Blues  United States
Lightning In A Bottle
diyAudio Member
 
Blues's Avatar
 
Join Date: Sep 2003
Location: The Milky Way
Quote:
Originally Posted by semi932 View Post
Think I got some bad irfp 240's and 9240's.
Just for experiment I used diode function and measured from Source to G and D.
On some I get about .450v give or take for brevity.

Others I get one measurement and OL from S to G.
These I think are bad.

Does this make any sense or am I grasping for straws?
Using the diode function you can check the D-S junction diode's integrity (N-type neg probe on D; P-type pos probe on D). It should be around 0.6V like any silicon diode junction.

A mosfet that already let out its magic smoke will have this diode junction fused together and will register a 0.0V reading.
__________________
Life simplified! Leap into the Warpspeed wormhole... http://www.6moons.com/audioreviews/warpspeed/1.html
  Reply With Quote
Old 1st June 2011, 09:47 AM   #8
h_a is offline h_a  Europe
diyAudio Member
 
h_a's Avatar
 
Join Date: Sep 2006
Location: Graz, Austria
Quote:
Using the diode function you can check the D-S junction diode's integrity
Yeah, true that's something to try.

Hannes
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Any one checked this Mosfet PCB? diptangshu Solid State 0 16th June 2010 09:32 AM
Have you checked out this site? mikee55 Solid State 3 14th February 2006 12:43 AM
pinoy diy checked it out dranreb&* Subwoofers 13 7th November 2004 07:35 AM
Vintage stuffed, checked this out! dranreb&* Multi-Way 3 23rd June 2004 10:15 PM
irf 240 or irfp 240 for the aleph scu Pass Labs 2 14th January 2002 06:49 PM


New To Site? Need Help?

All times are GMT. The time now is 11:46 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2