MTX Thunder302 FET problem

Cxrazy · 31st December 2007, 07:38 PM

Hey guys,

I recently blew out one of my FET's on my amp, so i purchased a replacement online, and then I soldered that sucker back in place.

I was really hoping that would fix it, but no, it was too easy.

Originally, only the FET on the far left was blown, so I replaced it with the one you see there. Now when I measure any of them with my ohmmeter its ~2-8ohms. So they're blown.

As you can see the chip on the left has 508 on it compared to the original chips 008. That mean anything?

Should I try and replace all 4 of the blown FETs or is the problem elsewhere?

Thanks for the help!

1moreamp · 31st December 2007, 08:15 PM

those are date codes for the build of the device. In a class D amp there should be little to no issues, unless the other fets were leaky then it will all fail again very quickly.
It looks like the 508 chip is touching the case at it tab end, now this could be a issue...

this appears to be a class AB type amp at first glance, if so then there are usually damage issues with the OK looking devices right beside the blown ones. I replaces entire sets on AB type amps, and on some D amps depending on its design....

Also in AB type amps damage likes to spread back into the driver stages, and sometimes all the way back to the Diff input of the main amp for each channel. The drivers are inexpensive so be ready to replace more to repair this amp...

Perry Babin · 31st December 2007, 08:52 PM

The tab of the transistor looks like someone grabbed it with a pair of diagonal cutters. If so, there are probably burrs on the bottom that can cut through the insulator and cause the amp to fail.

I don't know what you paid for the SSP45N20A but they're generally expensive (~$15 ea.). Something less expensive may work just as well. Of course, if you've found a source where you can get them for only a few $ each, use the original replacements.

Pull all of the outputs in that channel and test them out of the board. If you can find 2 that are OK, reinstall them in the two center locations and try to power up the amp. Have all of the transistors clamped down and use a 10 amp fuse in the B+ line when powering it up.

Cxrazy · 1st January 2008, 03:39 PM

I can get the chip for about $2 each, so its not a big deal to replace them all.

Thanks for the advice!

1moreamp · 1st January 2008, 04:12 PM

Please pray tell where...Thanks and Happy New Year !

Cxrazy · 1st January 2008, 05:21 PM

http://www.electronix.com/catalog/pr...ducts_id/14690

Cheers

Perry Babin · 1st January 2008, 05:49 PM

Cxrazy:

I suggest that you order the ones you need as soon as possible. These have been in high demand for a long time. Unless the distributor has many thousands on hand, they're likely to be bought-out very quickly.

Cxrazy · 1st January 2008, 08:04 PM

I ordered 6

Hopefully this fixes my problem...

Thanks for the help everyone!

1moreamp · 2nd January 2008, 02:45 AM

Thanks,,,,

jol50 · 2nd January 2008, 03:18 PM

Can he check the resistors while the transistors are out?

31st December 2007, 07:38 PM	#1
Cxrazy diyAudio Member Join Date: Dec 2007	MTX Thunder302 FET problem Hey guys, I recently blew out one of my FET's on my amp, so i purchased a replacement online, and then I soldered that sucker back in place. I was really hoping that would fix it, but no, it was too easy. Originally, only the FET on the far left was blown, so I replaced it with the one you see there. Now when I measure any of them with my ohmmeter its ~2-8ohms. So they're blown. As you can see the chip on the left has 508 on it compared to the original chips 008. That mean anything? Should I try and replace all 4 of the blown FETs or is the problem elsewhere? Thanks for the help!

31st December 2007, 08:52 PM	#3
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	The tab of the transistor looks like someone grabbed it with a pair of diagonal cutters. If so, there are probably burrs on the bottom that can cut through the insulator and cause the amp to fail. I don't know what you paid for the SSP45N20A but they're generally expensive (~$15 ea.). Something less expensive may work just as well. Of course, if you've found a source where you can get them for only a few $ each, use the original replacements. Pull all of the outputs in that channel and test them out of the board. If you can find 2 that are OK, reinstall them in the two center locations and try to power up the amp. Have all of the transistors clamped down and use a 10 amp fuse in the B+ line when powering it up. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

1st January 2008, 05:49 PM	#7
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Cxrazy: I suggest that you order the ones you need as soon as possible. These have been in high demand for a long time. Unless the distributor has many thousands on hand, they're likely to be bought-out very quickly. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

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
mtx amp problem [[help!!]]	fuzzypinkhat45	Car Audio	3	8th July 2008 05:34 AM
FRD/ZMA Problem	Twisted85	Multi-Way	5	4th December 2006 01:19 PM
p3a problem	MaXiZ	Solid State	17	16th July 2005 07:14 AM
GC amp problem	Jamh	Chip Amps	30	6th April 2004 02:50 PM


	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

31st December 2007, 08:15 PM	#2
1moreamp diyAudio Member Join Date: Dec 2005 Location: Northern California	those are date codes for the build of the device. In a class D amp there should be little to no issues, unless the other fets were leaky then it will all fail again very quickly. It looks like the 508 chip is touching the case at it tab end, now this could be a issue... this appears to be a class AB type amp at first glance, if so then there are usually damage issues with the OK looking devices right beside the blown ones. I replaces entire sets on AB type amps, and on some D amps depending on its design.... Also in AB type amps damage likes to spread back into the driver stages, and sometimes all the way back to the Diff input of the main amp for each channel. The drivers are inexpensive so be ready to replace more to repair this amp...

1st January 2008, 03:39 PM	#4
Cxrazy diyAudio Member Join Date: Dec 2007	I can get the chip for about $2 each, so its not a big deal to replace them all. Thanks for the advice!

1st January 2008, 04:12 PM	#5
1moreamp diyAudio Member Join Date: Dec 2005 Location: Northern California	Please pray tell where...Thanks and Happy New Year !

1st January 2008, 05:21 PM	#6
Cxrazy diyAudio Member Join Date: Dec 2007	http://www.electronix.com/catalog/pr...ducts_id/14690 Cheers

1st January 2008, 08:04 PM	#8
Cxrazy diyAudio Member Join Date: Dec 2007	I ordered 6 Hopefully this fixes my problem... Thanks for the help everyone!

2nd January 2008, 02:45 AM	#9
1moreamp diyAudio Member Join Date: Dec 2005 Location: Northern California	Thanks,,,,

2nd January 2008, 03:18 PM	#10
jol50 diyAudio Member Join Date: Nov 2007	Can he check the resistors while the transistors are out?

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

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