Help to repair JL audio 300/2 - Page 5 - diyAudio
Go Back   Home > Forums > General Interest > Car Audio
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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
Thread Tools Search this Thread
Old 19th March 2009, 08:49 PM   #41
diyAudio Member
Join Date: Nov 2003
Location: Louisiana
If the outputs failed in this channel, you need to check the gate resistors for the output FETs.

Is the small transistor between the output transistors OK?

If those are OK, you need to check the driver board components. Check the transistors Q8 and Q14 in the image below.

Click the image to open in full size.
  Reply With Quote
Old 19th March 2009, 10:18 PM   #42
sheim is offline sheim  United States
diyAudio Member
Join Date: Mar 2009
Default My Problem


As far as I can tell I am the first one to open up this JL Audio 300/2.The orginal problem was low volume at wide open.No large amount of heat at any of the fets.The small upright board with the 6 Green LEDS on it had some small transistor s that seem to be getting hotter then I would expect,but I removed these and they checked good.

With fets removed do all the pads for all 8 fets check the same as far as Drain,Gate , Source. Three pads per fet?

I have had this on without Heat sinks attached for 10-15 sec at a time, how much heat will they stand like this without doing damage to Them?

If the fets are checking good as far as voltage drop on Source drain junction and continuity can they still be bad? What is the best way to check fet w/VOM?

  Reply With Quote
Old 20th March 2009, 12:52 AM   #43
diyAudio Member
Join Date: Nov 2003
Location: Louisiana
Is the input voltage switch set to low and the gain set to the fully clockwise position?

With the FETs removed, all of the FETs should produce essentially the same readings when checking them (out of the board). I wouldn't know what to expect when checking the pads with the meter (FETs out of the circuit).

Depending on the current flowing through the FETs, they can overheat and fail within seconds. You shouldn't allow them to get too hot to touch.

When checking the FETs, follow the procedure on the following page:
  Reply With Quote


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
Cambridge Audio A5 repair job pulseezar Solid State 36 6th May 2012 02:06 PM
jl audio 300/4 repair brianfulcher15 Car Audio 3 16th June 2009 05:45 AM
lightning audio amp repair doughboi916 Car Audio 14 31st August 2007 09:05 PM
Atlas Audio Repair Helen Parts 2 31st August 2007 03:41 AM

New To Site? Need Help?

All times are GMT. The time now is 11:21 AM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2