help fixing class D amp..

jton219 · 27th August 2008, 12:43 PM

i own an infinity basslink powered car audio subwoofer. its a 10inch subwoofer powered by its own 200watt class D amo. the amp blew a few months ago. i havnt had the time to try to fix it until last week. i opened up the amp and saw a blown capacitor rated at 1000uf, 80v 105 degree c. i replaced the blown cap with a new one, tried firing up the amp and its still broken. i didnt see any other noticeable shorts on the board. don't know what to do next.

amp symtoms- power LED is on, the servo light (lights up to notify you when the woofer is at max excursion) blinks occasionally during heavy bass notes.. no output from the subwoofer, it blows 25a ato fuses all day. i remember hearing 2 or 2 loud non musical thumps from the woofer before it blew.

alexclaire · 27th August 2008, 01:15 PM

hi,
you gotta test output fets (probably one pair).

Probably blown (=shorted)

what about your woofer ?

did it survive to full DC supply ?

jton219 · 27th August 2008, 10:36 PM

please excuse my noobiness.. please explain how to test a mosfet. the woofer seems good..i hooked it up to a 9 volt batt and it responds.i actually get a new a/b amp in today that i going to try to use to bring the basslink woofer back to life.

Eva · 27th August 2008, 11:40 PM

The capacitor is not likely to be the main fault. It probably blew because the faulty circuit put too much stress on it (overvoltage, overcurrent or overheating of something close to it).

jton219 · 28th August 2008, 12:02 AM

do you guys think this thing is even worth fixing..or should i just dump it.

wakibaki · 28th August 2008, 12:27 AM

Given that you don't know how to test for a shorted FET, it's probably more economic to replace it, but economics is not always the whole story.

w

englishjg · 9th September 2008, 03:11 PM

Hi. I have the same issue. Unit powers on and just sits there. Anything anyone can suggest is greatl appreciated. $300. is an awful lot of money for me to simply throw it out and buy another one. I gotta try to fix this.
Thanks!
Jim

jton219 · 9th September 2008, 09:04 PM

it appears after blowing the amp, the speaker starts to go too. I hooked up the speaker to an external amplifier, resealed up the basslink so its air tight and it sounds really bad. the amp i'm using is from cadence and puts out 200 watts in bridge mode. it also causes the amp to go into safe mode after switching sources from radio to cd or whatever. some have told me the voice coil is starting to go and the amp and the impedance is lower than its spose to be, thats why someitmes the amp goes into safe mode.

Eva · 9th September 2008, 10:24 PM

Could you measure voice coil resistance with a multimeter? Remember to substract the result that you get when you join both test leads directly from the measured value.

Tekko · 9th September 2008, 10:36 PM

If it sounds bad, either the voice coil is half molten or the amp u hooked up is bad.

27th August 2008, 12:43 PM	#1
jton219 diyAudio Member Join Date: Aug 2008	help fixing class D amp.. i own an infinity basslink powered car audio subwoofer. its a 10inch subwoofer powered by its own 200watt class D amo. the amp blew a few months ago. i havnt had the time to try to fix it until last week. i opened up the amp and saw a blown capacitor rated at 1000uf, 80v 105 degree c. i replaced the blown cap with a new one, tried firing up the amp and its still broken. i didnt see any other noticeable shorts on the board. don't know what to do next. amp symtoms- power LED is on, the servo light (lights up to notify you when the woofer is at max excursion) blinks occasionally during heavy bass notes.. no output from the subwoofer, it blows 25a ato fuses all day. i remember hearing 2 or 2 loud non musical thumps from the woofer before it blew.

27th August 2008, 11:40 PM	#4
Eva diyAudio Member Join Date: Oct 2003 Location: Near the sea	The capacitor is not likely to be the main fault. It probably blew because the faulty circuit put too much stress on it (overvoltage, overcurrent or overheating of something close to it). __________________ I use to feel like the small child in The Emperor's New Clothes tale

9th September 2008, 03:11 PM	#7
englishjg diyAudio Member Join Date: Sep 2008	Basslink not working Hi. I have the same issue. Unit powers on and just sits there. Anything anyone can suggest is greatl appreciated. $300. is an awful lot of money for me to simply throw it out and buy another one. I gotta try to fix this. Thanks! Jim

9th September 2008, 10:24 PM	#9
Eva diyAudio Member Join Date: Oct 2003 Location: Near the sea	Could you measure voice coil resistance with a multimeter? Remember to substract the result that you get when you join both test leads directly from the measured value. __________________ I use to feel like the small child in The Emperor's New Clothes tale

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


	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

27th August 2008, 01:15 PM	#2
alexclaire diyAudio Member Join Date: May 2005 Location: Avesnes/Helpe	hi, you gotta test output fets (probably one pair). Probably blown (=shorted) what about your woofer ? did it survive to full DC supply ?

27th August 2008, 10:36 PM	#3
jton219 diyAudio Member Join Date: Aug 2008	please excuse my noobiness.. please explain how to test a mosfet. the woofer seems good..i hooked it up to a 9 volt batt and it responds.i actually get a new a/b amp in today that i going to try to use to bring the basslink woofer back to life.

28th August 2008, 12:02 AM	#5
jton219 diyAudio Member Join Date: Aug 2008	do you guys think this thing is even worth fixing..or should i just dump it.

28th August 2008, 12:27 AM	#6
wakibaki Banned Join Date: Jan 2008 Blog Entries: 2	Given that you don't know how to test for a shorted FET, it's probably more economic to replace it, but economics is not always the whole story. w

9th September 2008, 09:04 PM	#8
jton219 diyAudio Member Join Date: Aug 2008	it appears after blowing the amp, the speaker starts to go too. I hooked up the speaker to an external amplifier, resealed up the basslink so its air tight and it sounds really bad. the amp i'm using is from cadence and puts out 200 watts in bridge mode. it also causes the amp to go into safe mode after switching sources from radio to cd or whatever. some have told me the voice coil is starting to go and the amp and the impedance is lower than its spose to be, thats why someitmes the amp goes into safe mode.

9th September 2008, 10:36 PM	#10
Tekko diyAudio Member Join Date: Jan 2005	If it sounds bad, either the voice coil is half molten or the amp u hooked up is bad.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Fixing the R30	bjackson	Multi-Way	3	16th May 2010 06:10 AM
Need some help fixing this amp	mazeroth	Solid State	1	13th May 2008 03:04 AM
Need Help Fixing an old NAD 304	li_gangyi	Solid State	14	8th December 2004 07:59 PM
Help! Fixing Amp.	shajan	Solid State	20	29th May 2004 08:06 AM
Fixing Cabinet	techno	Multi-Way	2	15th August 2001 02:04 PM

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