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

Solid State Talk all about solid state amplification.

Quad 405-2 Problem
Quad 405-2 Problem
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 July 2010, 02:23 PM   #1
pborlace is offline pborlace  United Kingdom
diyAudio Member
Join Date: Oct 2006
Default Quad 405-2 Problem

Hi, I wonder if anyone can help me with this. One of my boards M12565 iss 6
has blown R38. When switched on the resistor glows bright red at which point I switch off! I've read the Quad service data and have checked D5 and D6 which it states may cause the problem. I unsoldered them and they are fine.

I'd be grateful for any assistance with this.

Thanks for looking
  Reply With Quote
Old 9th July 2010, 04:21 PM   #2
Aldotin is offline Aldotin
diyAudio Member
Aldotin's Avatar
Join Date: Dec 2009

Check output DC offset voltage (meausure voltage on +/- speaker terminal)
  Reply With Quote
Old 9th July 2010, 04:35 PM   #3
cda is offline cda
diyAudio Member
cda's Avatar
Join Date: Jun 2010
Also check R7 and R8, they are rated very conservatively, and should be replaced with metal oxide resistors of (at least) 1W.
  Reply With Quote
Old 9th July 2010, 04:47 PM   #4
405man is offline 405man  Scotland
diyAudio Member
Join Date: Dec 2003
Location: South Lanarkshire near Glasgow Scotland
I would disconnect the DC offset protection by unsoldering the blob next to the output terminal then check the output offset voltage, this should be a few mV. The CD protection triac goes s/c. Then I would check both supply voltages and the supplies to the opamp.

  Reply With Quote


Quad 405-2 ProblemHide 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
Quad 405-2 Problem pborlace Solid State 30 12th December 2012 10:54 AM
Quad 405 output voltages problem vzs Solid State 32 11th December 2011 10:29 PM
quad 44/405-2 another hum problem graeme uk Solid State 8 6th July 2007 07:49 AM
Quad 405 hum problem vzs Solid State 16 7th June 2006 10:26 AM
Quad 405 problem emperor Solid State 5 14th July 2005 11:09 AM

New To Site? Need Help?

All times are GMT. The time now is 07:19 AM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio