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

MTX Thunder 4160 Repair
MTX Thunder 4160 Repair
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 21st September 2007, 12:53 PM   #1
ECM is offline ECM  United States
diyAudio Member
Join Date: Jul 2004
Location: Dubai
Default MTX Thunder 4160 Repair

I have here an MTX Thunder 4160 amplifier that is defective. The two power supply fets were missing, so I replaced them with 60n06 types. The resistors were burned and those will get replaced with 62 ohm parts. I have an extra 4160 so it was easy to cross reference and replace the missing/burned parts.

My question is about biasing. Two BUZ11 outputs failed which I think led to the power supply failure (FEN/FEP diodes are good). I purchased some replacement BUZ11 but they are obviously from a different batch than the originals. Will I have to rebias the outputs after replacing them? Since three channels appear to be good, can I measure the voltage drop across the large drain resistors and then adjust the repaired channel to match?
  Reply With Quote
Old 21st September 2007, 07:32 PM   #2
Perry Babin is offline Perry Babin  United States
diyAudio Member
Join Date: Nov 2003
Location: Louisiana
Before you apply power, turn the bias control for the defective channel to the fully counter-clockwise position. If the threshold voltage for the new transistors is lower than the old ones, the original bias settings may cause excessive current flow which could cause the new FETs to fail. Clamp the transistors to the sink in case there are other problems that could cause the FETs to overheat.

If the bias setting on the other channels is high enough to read with your voltmeter, using the same settings for the new channel would be OK. If the voltage is too low across the resistors, turn the bias clockwise until you just barely see an increase in idle current (on the amp meter of your DC power supply) and then back off of the biasing just a bit.
  Reply With Quote
Old 19th November 2007, 10:55 AM   #3
ECM is offline ECM  United States
diyAudio Member
Join Date: Jul 2004
Location: Dubai
Thanks for the info Perry.

I ran the amp up with a battery instead of my power supply since I was having issues with it.
I was able to measure the voltage across both drain resistors of the good channels and adjusted the bias on the repaired channel to match.

The voltages across the resistors on the good channels are +/- 1.4mV and the repaired channel had +/-5.5mV. With the bias pot, it was easily adjusted to +/-1.4mV as well. Now they all match.

DC offset of good channels is -24mV, 13mV, and -10mV. Repaired channel is 8mV. All referenced to ground and measured at speaker terminal.

Power supply DC rails are a solid +/-24.0 volts. I don't have a scope to check out the waveform though. Transformer didn't buzz or get hot and neither did the fets.

After everything checked out, I connected a speaker and all channels produced clear sound. Amp worked in bridged mode too. Next up is a full power operational check with a couple 6.5's and a sub.
  Reply With Quote


MTX Thunder 4160 RepairHide 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
MTX Thunder 421D spooney Car Audio 5 19th April 2008 03:40 AM
MTX 4160 and DC power supply interaction ECM Car Audio 3 12th October 2007 06:46 PM
Mtx Thunder 2300 vypr Car Audio 35 21st September 2006 07:35 PM
Thunder and lightning Netlist Everything Else 9 22nd August 2006 05:39 AM
Thunder and lightning. In jleaman Everything Else 3 8th July 2003 07:12 AM

New To Site? Need Help?

All times are GMT. The time now is 02:22 AM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 16.67%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio