Amplifier bad, 37 VDC at the speaker output - diyAudio
Go Back   Home > Forums > General Interest > Car Audio

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
Reply
 
Thread Tools Search this Thread
Old 20th January 2011, 08:07 PM   #1
bernat is offline bernat  Europe
diyAudio Member
 
Join Date: Dec 2008
Default Amplifier bad, 37 VDC at the speaker output

Hello, I bought this amplifier from Ebay in "perfect working shape", is a MAcrom Synthesis 1000, when arrived at home I opened the case and looked inside , the layout looked good with no visible burned components .... well ,that seems good I was thinking, then I connected to a power supply and the control led turns green, Perfect !!! now starts my stupidity, connect to my expensive home loudspeakers for test and ..... nothing ... well , yes ... a maravellous smell a fried voice coils ! I take the multimeter and check 37 V at both speakers outputs, all the rail voltage of the power supply goes directly to the speakers, seems the amplifier dont have DC output offset protection circuit. I've tried to repair but my knowledge of electronic is minimal.
After inspection of the bottom side I can see the amplifier was tried to repair before, the mosfets in the PS are replaced and the board nea them is burned.
I have been searching a lot about DC current output and I was thinking in shorted output transistors , pre-drivers and drivers. I REPLACED ALL OF THEM, INCLUSE THE MOSFETS for the same model of transistors installed before and I'm still having 37VDC in the outputs. Now I dont know what more to change.

Can some one give me help?

Thanks
Attached Images
File Type: jpg P1040271_1.jpg (348.0 KB, 88 views)
File Type: jpg P1040272_1.jpg (300.8 KB, 85 views)
File Type: jpg P1040273_1.jpg (428.2 KB, 81 views)
File Type: jpg P1040274_1.jpg (259.0 KB, 73 views)
  Reply With Quote
Old 20th January 2011, 08:15 PM   #2
diyAudio Member
 
Join Date: Nov 2003
Location: Louisiana
What's the DC voltage on the center legs of the TIP35s?

What's the DC voltage on the center legs of the TIP36s?

What's the DC voltage on pin 8 of the 8-pin op-amps (all should be very nearly the same - confirm)?

What's the DC voltage on pin 4 of the 8-pin op-amps (all should be very nearly the same - confirm)?
  Reply With Quote
Old 20th January 2011, 08:38 PM   #3
bernat is offline bernat  Europe
diyAudio Member
 
Join Date: Dec 2008
Thanks Perry for the fast reply,

tip 35 35v

tip 36 36.8v

and when I was disposed to measure the op amps the amplifier started to go into protection, I believe some thing more is now broken, I will check the mosfets now

Last edited by bernat; 20th January 2011 at 09:03 PM.
  Reply With Quote
Old 20th January 2011, 09:30 PM   #4
diyAudio Member
 
Join Date: Nov 2003
Location: Louisiana
IS the voltage on the TIP36s a negative voltage?

Are the two in the center op-amps? I'd suspect that they're opto-couplers.

There appear to be op-amps on the vertical boards. Check those and any others in the amp.
  Reply With Quote
Old 20th January 2011, 09:40 PM   #5
bernat is offline bernat  Europe
diyAudio Member
 
Join Date: Dec 2008
Now is imposible to take measures, the protection led is flashing every second green-red-green-red ... the two opamps in the center has 6 legs and the inscription says 4N36 836ATK63
  Reply With Quote
Old 20th January 2011, 09:44 PM   #6
diyAudio Member
 
Join Date: Nov 2003
Location: Louisiana
Yes. Those are opto-couplers.

Did an output transistor fail (short)? Check them all.
  Reply With Quote
Old 20th January 2011, 09:54 PM   #7
bernat is offline bernat  Europe
diyAudio Member
 
Join Date: Dec 2008
I replaced the 20 transistors with new ones of the same batch, I noticed some of them was replaced before (different brands mixed, mospec and ST).
Maybe they are broken again, I will desolder them and check
  Reply With Quote
Old 20th January 2011, 11:15 PM   #8
diyAudio Member
 
Join Date: Nov 2003
Location: Louisiana
You can make a quick check without removing them.
  Reply With Quote
Old 21st January 2011, 08:46 AM   #9
bernat is offline bernat  Europe
diyAudio Member
 
Join Date: Dec 2008
Perry, your web site is fantastic, thanks for share your knowledge.

Tomorrow I will check the tip36-36 and the mosfets following your tutorials
  Reply With Quote

Reply


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
Logitech Z-5300: Amplifier has a bad satellite output spongebue Solid State 5 21st February 2011 09:46 PM
Dragster Amplifier bad SMPS ben12345 Car Audio 38 4th February 2010 04:22 PM
Capacitors 37,000 uF at 75 VDC and 85C lgreen Swap Meet 1 23rd December 2009 07:50 PM
12 vdc to 18 vdc isolated P-P jamesrnz Power Supplies 89 4th February 2009 04:36 PM
Is my Sub's speaker bad? WBFAir Subwoofers 1 17th March 2007 02:43 PM


New To Site? Need Help?

All times are GMT. The time now is 09:46 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2