mtx 7801 power transformer - 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 3rd April 2007, 07:05 AM   #1
diyAudio Member
Join Date: Apr 2007
Default mtx 7801 power transformer

my old mtx 7801 went up in smoke (the one i can use for parts)
i replaced the power input transistors originally huf73559p? with irzf48's and applied power to the amp again only to hav it start smoking as soon as i applied power but this time it was from the power transformer. lokked at it and the enamel on like 4-5 of the wires was melted together and some bare wire showing. so i guess i need a new power transformer and ill check the transistors again to make sure theyre good. is there anything else i should check for? where can i get the transfomer? nay help will be much appreciated!
  Reply With Quote
Old 3rd April 2007, 08:37 PM   #2
diyAudio Member
Join Date: Nov 2003
Location: Louisiana
If you can get a replacement transformer (or if you rewind the one you have), you need to check the driver transistors (Q102-Q105) that drive the FET driver transformer (small toroidal transformer near the TL494 driver IC). Also check resistors R111, R112 and resistors R138-R141.

The original FETs were likely HUF75339P3s.
  Reply With Quote
Old 4th April 2007, 08:06 AM   #3
diyAudio Member
Join Date: Apr 2007
thanks for the help and everything. i shecked all of the stuff you told me to on the board and its not worth my time and effort to fix it. called mtx they said that they charge a $98 flat rate to fix these things so i think im gonna ship it to them and just have them fix it so i know its good to go.
  Reply With Quote
Old 27th March 2008, 07:53 AM   #4
Account disabled at member's request
Join Date: Mar 2008
Default mtx 7801 Newbi

New to this site and dunno how to post anything yet... But for starters, Mtx 7801 amp. Fans failed and so far it seems like the 8 voltage regulators blew... No black spots or anything on the mother board that I can see... Included are pics. Question is- Should I be looking for anything else with the naked eye to be burnt or blown up??? Had the Radio Playing while i was replacing the Throttle body that I bored, and all of a sudden the subs quit hitting... Turned everything off and smelt the amp burnt... Any help answers will be greatly appreciated thanks again...
Attached Images
File Type: jpg picture 085.jpg (73.7 KB, 117 views)
  Reply With Quote
Old 27th March 2008, 08:15 AM   #5
diyAudio Member
Join Date: Nov 2003
Location: Louisiana
The capacitors are missing. Are those the 'voltage regulators' you're talking about?

The inductor (near the caps) looks broken.

Have you read this thread?
MTX TA7801 repair

Have you checked any of the heatsink mounted transistors?
  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
Power transformer Alain Dupont Tubes / Valves 4 4th April 2005 09:12 PM
Transformer ok for power amp?? 6502dude Solid State 7 3rd April 2005 01:02 PM
Power Transformer tenderland Tubes / Valves 1 19th January 2005 06:42 PM
toroid Transformer as power Transformer for tube tone Tubes / Valves 7 11th February 2003 08:57 AM
Good price on huge power transformer for power amp. G Solid State 3 15th September 2002 01:23 PM

New To Site? Need Help?

All times are GMT. The time now is 03:47 PM.

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