Mosfets

[01xtreme]

Well thats not the case this time

I have blown many many many amps. LoL

Some either blown because of under voltage, over voltage, crazy low impedance loads, faulty rca's, no protections circuit (sub blew and that took the amp with it), and sometimes just the I dont know what happened Lol

I delt with 3 companies so far db-r, arc, and cia (cia is horrid never again!. A+++ to db-r and arc for pricings, but db-r is a very busy place where the sundowns get repaired first then the consumer sent in amps, youll be waiting a bit for your amp back. and arc is seeming to be very reliable, decently fast, and great price)

But no matter what amp I had in for any repair when I knew the fets where popped, other things needed repair attention too. No amp just ever needed new fets only.

There was a reason that caused your mosfets to get extremely hot, when they get too hot its usally due to being worked to hard, it maybe a clipped signal, it maybe a impedance ohm to low, it maybe that its power acoustik and them being cheaper they used low grade mosfets to keep cost down.

I dont know what else to say, but most likely your gonna end up spending the cash on new mosfets, put them in the amp, get it all back together, power it up, and poof again. Then youll be out more cash.

I would buy the nicest fets you can buy if your still gonna attempt the repair yourself, they will last longer, and most likely make the amp a little more stable.

Also it is wise to replace all mosfets at once. If its the power supply mosfets, replace them all. If its the output mosfets, replace them all.

If theres 6 powersupply fets on the left side of the board, but only 3 are burned you should at least replace all 6, if you cant afford to do all 12 (left and right side).

The reason for doing them all is because you run the chance or risk of having a different date code or brand and date mosfet completely different then what you currently got. If you buy the nice fets and put them in a pcb with the older weaker fets you will get no real gain in spending the extra cash.

Best of luck to you, and hopefully just the fets are actually needing repair. I expect updates and pics, this has the potential for a great do it yourself thread

Thanks. If I end up repairing it myself, you can bet on a thread. I do plan on replacing all the fets for the power supply, 16 on that side. We will see. I am thinking this is too close to the show to attempt, but who knows. It all depends on how im feeling in the morning. Im just pissed it blew up cause I had quite a few people wanting to hear my new setup, and of course, i blow an amp.

[audiofanaticz]

Im just pissed it blew up cause I had quite a few people wanting to hear my new setup, and of course, i blow an amp.

trust me, thats always how it is!!

[Boon]

not questioning you at all, but what is leading you to believe the drive is bad? I was beating the shit out of the amp, then POP. started smoking. Im not sure if it helps determine anything, but the amp still turned on and the fan would run, but it just made no sound.

I'm a bit amazed it still turns on, usually when FETs blow they go short circuit and pop your power fuses.

I suspect the drive because on class d amps and the power supplies of any amp some part of the drive very commonly fails when the FETs do.

Most of the time the FET shorts out when it pops and the drive circuit desperately tries to turn the FET off but it can't supply enough current to do so and it pops too. What stops this from happening is either a very sturdy drive circuit that can survive long enough for the amp to shut itself down or when a component between the drive and the FETs blows up first and saves the drive.

Because your amp still turns on I would be willing to bet that the blown FETs have burnt the drain leg right off the silicon inside so they're not causing a short but it also sounds like your drive is indeed blown because the amp turns on but makes no sound which says to me that the output section is getting no power or is also damaged.

Amps use lots of FETs in parallel and will actually turn on and run ok (at very low power) with half the FETs missing from the power supply section.

I suppose you could check the DC voltage on each rail of the output side after cutting out the visibly bad FETs... if it's 0v then the drive is almost certainly farked. If it's fairly high (Probably about 60-90v on this amp) then the power supply is working somewhat OK but the output is somehow broken.

As I have said several times before, if you don't have an o-scope you're literally blind. There's a whole lot of stuff you have to check to even decide if an amp is repairable.