Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Chip Amps Amplifiers based on integrated circuits

Please help me repair this amp.
Please help me repair this amp.
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 9th August 2011, 03:49 AM   #1
MotorMouth93 is offline MotorMouth93  United States
diyAudio Member
Join Date: Aug 2011
Default Please help me repair this amp.

Hi Everyone,

I was given an Altec Lansing inMotion IM7 a while back and I accidentally shorted the built in subwoofer amp. One of the IRF7379 chips caught fire and two other small components were also damaged. I replaced the 7379 chip and the amplifier was partially working but the sound was very "muddy" and there was a constant crackling noise. I removed the other two damaged components entirely and the sound quality improved, most of the crackles went away but the sound is still not very clear. The problem is that I have no idea what to use to replace the two small components (outlined in the picture below) The upper one reads "KA2" and the lower reads "Z 2".

Click the image to open in full size.

I haven't been able to find anything other than that they are bipolar junction transistors. Does anyone know of a suitable replacement for these? Everything works perfectly, including the amps for the two main speakers, except for the sub amp. Thanks in advance!
  Reply With Quote
Old 9th August 2011, 05:39 AM   #2
palstanturhin is offline palstanturhin  Finland
diyAudio Member
palstanturhin's Avatar
Join Date: Jun 2011
KA2 could be a diode, replace with 4148
Z 2 may be a zener, measure the voltage from a working circuit...
  Reply With Quote
Old 9th August 2011, 05:48 AM   #3
tauro0221 is offline tauro0221  United States
diyAudio Member
Join Date: Nov 2008
Location: Victoria,TX
Did you check closely the Q9 and D20. It is look like burned out or something happened in there. The Q9 chip is close to L6 or next capacitor C58 or 50. I can not read the number right. Do you have an schematic?
  Reply With Quote
Old 9th August 2011, 05:24 PM   #4
MotorMouth93 is offline MotorMouth93  United States
diyAudio Member
Join Date: Aug 2011
Thanks for the help!

The Q9 chip is an IRF7379, it looks messed up because I replaced it. When the original one burned, it damaged two of the solder pads (upper left) and they came off. I had to improvise to make the connections.

I decided that since it didn't work anyway that I would take the KA2 and Z 2 parts from elsewhere on the board (I took them from the left channel), and the sub still doesn't work properly. It sounds great when turned down low but when the volume is turned up it is very distorted and muddy. I guess that other components were damaged also. I don't know a whole lot about this sort of thing so is there any other components I could check or is this board pretty much dead? Thanks!
  Reply With Quote
Old 12th August 2011, 11:08 PM   #5
tiefbassuebertr is offline tiefbassuebertr  Germany
diyAudio Member
tiefbassuebertr's Avatar
Join Date: Jul 2005
Location: D-55629 Schwarzerden
Use for the headline this:
Altec Lansing inMotion IM7 - damaging IRF7379 and file this topic about "class-D"
Then you will receive much more advices.
Attached Images
File Type: jpg Altec Lansing inMotion IM7 front.jpg (67.4 KB, 63 views)

Last edited by tiefbassuebertr; 12th August 2011 at 11:13 PM.
  Reply With Quote


Please help me repair this amp.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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
B&K AVR-202i DIY repair possible? Relays buzzing (I think) - otherwise normal? ZepOfLed Solid State 84 8th August 2009 05:46 AM
Amp Repair -- DC detector? Amp only works right at high volume? Help? danielwritesbac Solid State 9 2nd January 2008 06:05 PM
NEED HELP!! Vintage B&W 800 ASW repair/modify dritter_1999 Subwoofers 2 5th April 2006 12:50 PM
Repair/replace 30-year old B&W DM6 woofer? jacques54 Multi-Way 7 20th December 2005 09:31 PM

New To Site? Need Help?

All times are GMT. The time now is 06:43 AM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio