Quad 405-2 Problem

pborlace · 9th July 2010, 01:23 PM

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
Peter

Aldotin · 9th July 2010, 03:21 PM

Hi!

Check output DC offset voltage (meausure voltage on +/- speaker terminal)

cda · 9th July 2010, 03:35 PM

Also check R7 and R8, they are rated very conservatively, and should be replaced with metal oxide resistors of (at least) 1W.

405man · 9th July 2010, 03:47 PM

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.

Stuart

9th July 2010, 01:23 PM	#1
pborlace diyAudio Member Join Date: Oct 2006	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 Peter

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Quad 405-2 Problem	pborlace	Solid State	30	12th December 2012 09:54 AM
Quad 405 output voltages problem	vzs	Solid State	32	11th December 2011 09:29 PM
quad 44/405-2 another hum problem	graeme uk	Solid State	8	6th July 2007 06:49 AM
Quad 405 hum problem	vzs	Solid State	16	7th June 2006 09:26 AM
Quad 405 problem	emperor	Solid State	5	14th July 2005 10:09 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? 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

9th July 2010, 03:21 PM	#2
Aldotin diyAudio Member Join Date: Dec 2009	Hi! Check output DC offset voltage (meausure voltage on +/- speaker terminal)

9th July 2010, 03:35 PM	#3
cda diyAudio Member 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.

9th July 2010, 03:47 PM	#4
405man 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. Stuart