Help needed please, blown fets :(

[badarsebikerst 10+ year member]

So as some of yall may know, I have an mtx 1501d and of course its been modded and cruising down the road today, the remote wire came loose and touched onto the negative speaker terminal. You know when you mod these amps you're actually removing the protection circuit to left them run at lower impedence and higher voltage. So yeah it blew a nice little rail of my fets.

The thing is...

It plays just fine! You can't tell anything fucked up but me and my ocd now knowing something ain't right just can't take it so I gotta do something about this.

So anyways what can I do about this? Just try to search for replacements for the blown fets and replace them? Or replace the whole side of fets, or replace all the fets in the amps with same ones or possibly bigger and better?

Any amp gurus in here with suggestions? Heres: pics

Discuss?

Click to read more...

 

[morespl 10+ year member]

replace the four screwed up ones heres a place to get parts Allied Electronics

 

[Audiohazzard 10+ year member]

^^^^ this!!! A good place is Electronic Components Distributor | DigiKey Corp. | US Home Page

 

[Spooney 10+ year member]

You have to replace all of the fets that are in parallel with the ones that are blown if you want it to be reliable. The ones that are toasted are some of the power supply fets. I would think that there are more than four in parallel in an amp of this size. I would personally change all the ones with that same part number. You are going to want to search at either mouser or digikey for an HUF75339P. That is the full part number for that fet. You will also want to check the gate resistors connected to the first leg of each of these fets and the smaller power supply driver transistors that drive these fets. The power supply driver chip could be suspect as well. If you had an oscilloscope it would be easy to see if the power supply driver IC is putting out the correct signal.

 

[bubbagumper6 5,000+ posts]

You have to replace all of the fets that are in parallel with the ones that are blown if you want it to be reliable. The ones that are toasted are some of the power supply fets. I would think that there are more than four in parallel in an amp of this size. I would personally change all the ones with that same part number. You are going to want to search at either mouser or digikey for an HUF75339P. That is the full part number for that fet. You will also want to check the gate resistors connected to the first leg of each of these fets and the smaller power supply driver transistors that drive these fets. The power supply driver chip could be suspect as well. If you had an oscilloscope it would be easy to see if the power supply driver IC is putting out the correct signal.

This guy knows his stuff //content.invisioncic.com/y282845/emoticons/fyi.gif.9f1f679348da7204ce960cfc74bca8e0.gif

 

[akheathen Premium Member]

....... something just doesn't add up......... you put power to the negative speaker output, and it fried 4 fets...... it sounds more to me like you blew a channel. either way, you need to map the circuit, and replace the resistors, diodes, preamp transistor, etc..... and make sure it's ballanced with the other side. when you go online to get the new fets, mouser can cross it over, and you can match it to something bigger than a to-220, and you can get better heat transfer. it appears you have plenty of room, but a mount tab might not clear on top

 

[Spooney 10+ year member]

I wouldn't try to put anything other than exact replacement parts in this amp. Class D amps can be very touchy with replacement parts even if they are supposedly superior or equivalent. Sometimes even new batches of the original parts are different enough spec wise to cause problems. Being that it is power supply fets it makes things a little easier. I would just hope there aren't any problems in the output section to go along with the bad PS fets.