MTX MiTEK Thunder4250D blown

[mbates14]

im glad someone knows... because i dont have a ******* clue. a schematic would be nice. lol.

 

[Perry Babin]

The circuit is very similar to the output stage of the Sony XM-D---P5 amps. The audio circuit on page 2 of the PDF file below shows you basically what you have.
http://www.bcae1.com/temp/xmd400p5schem.pdf

 

[mbates14]

thats a complicated little sucker. lol. mine only has 2 outputs. not 4, but i get the general idea.

 

[brandes.cm]

Here is the thread I started for a 421D. May add some insight or just waste your time!

http://www.diyaudio.com/forums/car-audio/152275-mtx-421d-issues.html

 

[mbates14]

I doubt its gonna waste my time. any info is good info, especially with class-D amps. this is only the second one ive seen in my entire lifetime, so its all new to me.

 

[Perry Babin]

If you want more information on similar amps, look up the 6500d threads.

 

[mbates14]

if its the big large amp, i think the last one i worked on was a 6500D. it had similar issues, one shorted output, blown gate resistor, and all 8 power supply transistors were blown.

I used a 73343 to replace the 73335, which are the same thing, except the RDS(on) of the 43 is much lower, making it more efficiant, less heat. worked better.

I got away with replacing the single output in that one also, and it worked fine. no issues out of that amp. just this stupid amp i got here now....

 

[mbates14]

Here are pictures of the amp (after mosfets shorted again and blew its resistors)


http://0ki.info/uploads/d3e2801ffd.jpg

http://0ki.info/uploads/fc16338aeb.jpg

 

[mbates14]

so does it look similar to anything?? do the caps look like they need changed?

 

[Perry Babin]

It's similar to the 6500d but has fewer parts.

If you have to order parts, you may as well order new capacitors. They're likely OK but it appears that they may have overheated.

 

[kevinkr]

<snip> do the caps look like they need changed?

They look like they got real hot, and the tops appear to be bulging which to me signals a need for immediate replacement.

 

[mbates14]

yea they are overheated alright, but why?

 

[Perry Babin]

Typically, they overheat when the amp is driven into a speaker load lower than lowest impedance load recommended for the amp. They can also fail when the inductors short or otherwise fail but yours looks like it's in good condition.

 

[mbates14]

someone probably "pounded" the hell out of it and that was it.

 

[brandes.cm]

It looks just like a 421D that I have. I marked the pic with the parts that were bad on mine. The three caps on mine were bulged and the two smaller ones that flank them were blown off the board. The opamp was the main cause of my output problems.

cory