What's wrong with this amp? PICS inside

[shizzzon 10+ year member]

Here is the situation, amp is irrelevant, here is the scene-

Stock alternator, car on, over 14v at idle, starting battery up front, XS D3100 batt in the back(reads 13.0 float), so i gots plenty of battery power for this amp which requires a 200A fuse.

I start to oscope the amp on a 48hz tone set to repeat.

Every now and then, there would be a "THUD" sound that would quickly come from the amp. Unknown as to why but we continue to scope anyway. I do not know if it's relevant or not.

Anyways, subsonic set to off, LPF set all the way up, bass boost OFF, phase 0, gain - all the way DOWN.

All settings on HU were flat, sub preout set to 15, Kenwood HU. Volume goes to 35.

I start the scoping process-

I want the user to reach a volume of 27 before i start turning up the gain.

Once he reaches approximately volume 20-22, this amp audibly appears to be outputting some decent serious power considering the gain is all the way down!

Once the volume is adjusted just a couple more notches, not even reaching 27 yet, here is what i know-

Voltage output on speaker leads- 28.5-28.7v (rated at 1.8kw@1ohm so not all the way there yet)

Sine wave on scope was still 100% clean.

immediately there was a "click" inside the amp as if something was switching then immediately smoke poured out the speaker wire\power\ground side.

The amp was extremely hot on the power\ground side.

Amp was taken apart and here are the pics-

Before i show pics, there was a chip that was cracked with model number - KIA494AP = Korea Voltage Mode PWM module Controller is what i pulled from it.

that and multiple FETs are fried, here are pics-

And of the Chip, looks like a resistor got fried too-

Click to read more...

 

[thegreatestpenn 5,000+ posts]

you burnt up a rail of fets. there's a number of reasons of how it happend

 

[shizzzon 10+ year member]

well, not me, but what i'm wondering is, what would cause this?

Voltage high, voltage out on speaker leads clean signal but not full clean output yet... but it died?

And with a burnt chip... why?

 

[TNTR70 10+ year member]

that looks pretty un-fixable to me..not worth the money to fix all that burnt up stuff

 

[thegreatestpenn 5,000+ posts]

voltage was too high, probably blew a cap and the cap being open led to burnt fets

 

[oldschoolboomer 10+ year member]

resistor number 202 got scovilled and sent micro pulse current to the johnson valve (not a good thing most of the time).

 

[shizzzon 10+ year member]

if i agree that's what happened, then the amp was due to failure VERY soon.

Amp's capable of running up to 42v out on clean signal, we almost reached 29v before it clicked then smoked.

 

[Engine_hp 10+ year member]

dude its totally ****ed.

 

[mario305]

ive never seen a whole side of fets get burt up only 2 or 3, wow u must have had a lighting bolt power that amp!

 

[MakeshiftAudio 10+ year member]

Your SMPS ****ed over, you probably need to redo the whole SMPS, since your voltage regulators probably died as well.. That explosion damage isn't bad, easily fixable.

Now, as for why it overheated... Was this on a load, or was it free scoped? Did you have a speaker terminal hooked to scope ground?

The thuds were probably the mosfets blowing open.

Edit: I've had a whole SMPS blow up, 16 fets blown to pieces. It was in shambles, but I got it working again. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif Reliable too.

 

[shizzzon 10+ year member]

The amp was loaded. 2 subs wired down to 0.6 DCR tested at amp.

Oscope wired probe on positive terminal and scope ground clamp on negative terminal.

OH and to add about the thuds, the Thuds were happening at volume levels BELOW 10. This was when the system was barely audibly outputting any sound while the scope was being set on the screen.

The thuds stopped about 3-4 minutes before it went up in smoke and all at low volume levels.

 

[MakeshiftAudio 10+ year member]

If you have AIM, it would be much easier and faster. I want to say your SMPS wasn't working properly.

 

[cx-7heaven 10+ year member]

The amp was loaded. 2 subs wired down to 0.6 DCR tested at amp.

This would be why manufacturers do not recommend going below a certain impedance. I'll be willing to bet that was a 1 ohm stable amp, not .5 ohm... recommended anyway.

 

[MakeshiftAudio 10+ year member]

Yeah. It could be as simple as that. I didn't even think to ask what amp it was.

 

[cx-7heaven 10+ year member]

Being that he says amp is irrelevent possibly means something cheap or unpopular