Phoenix Gold Phorum

hi guys new to the forum and was driving along when my subs stopped.... hmmm pulled over. amp was flashing in fault mode.. shut off car check all connections.. seem good, start car back up popping and smoke.... ugh .. unhook it all, drive home, get tere annd rip it all apart.. blew 7 out of the 8 mosfets in the power circuits, i have ordered replacement parts for them and picking up tommora but was wondering if anyone would happen to know any other possible causes for this ... thanx for any input.. also are these multilayer boards or just dual? thanx

Man that sucks! I'm sure someone will chime in with some possible answers for you. I'm not the tech type, but there are several on here who are.

Welcome to the Phorum, sorry it couldn't have been under happier circumstances.

i'm not nearly as knowledgable as many of the fellas on here, but to me it seems like an internal malfunction of the amp (and if it's really new then that seems even more likely). I think that if an external source "tried" to cause the problem, then the amp's fuse would have blown and protected it. I hope one of our many engineer types chime in for ya...good luck and welcome!!

Oh My God, Oh My God, Oh my God... The fets don't blow by themselves. They most likely failed because of a blown output fets.

So just fixing the power supply is a incomplete repair and it will surely let the smoke out again when you test fire it.

What was it fused at when Jesus made the smoke come out ??? A proper fuse should have prevented this from happening, but none the less it happens.

The amp failed a output IMO... and Then when you restarted it the power supply said OK hes running a 1 ohm load or less and shot full power through to the shorted outputs and Viola power supply smoke to follow the bad outputs... happens to all brands and all the time... so without any more info on the install the load speaker, the fuse inline to it, I think I am close to whats happened here.....


PG has flat rates, and if it was installed by a PG dealer it has longer then normal warranty.
Is there any more info on load, and fuses, and the such???? After I am guess like a lot here without more info to clear the picture more....

ouch, yep i sounds like cecil's right. the XE.load "senses" the load upon startup and likly gave it everything it had.

(you can also use this method in a more controlled setting to get more power out of them amp semi-safely)

so does all that mean i was sorta right:) or waaay wrong:(

its sounds like both


an external force fried output stage, then when he restarted it, the power supply blew up because of the already fried outputs

i see....bummer...why didnt his amp fuses or inline fuse (assuming he used one) protect the output stage from assault by the external source?...just scrounging for knowledge here

ok...so it's likely that his in-line fuse was rated too high. if that's the case, then i'll assume that the amps fuses arent guaranteed to protect the output stage (or for some reason they were too big also).

capitolj80 wrote:ok...so it's likely that his in-line fuse was rated too high. if that's the case, then i'll assume that the amps fuses arent guaranteed to protect the output stage (or for some reason they were too big also).

No , No, No, You see I ask what size fuses were inline because I see over fusing all the time, I also see one fuse at the battery and NO fuse at the amp. well this is a problem, its not correct.

So I ask questions trying to find the most likely reason why a FUSE did not protect your interests here. I am double fused in my system. Most install diagrams and well trained installers know that this is a must do to protect both car and equipment.

Now, your output stage probably lost one fet at first, but this condition will spread due to the design of the output stage. This is not brand specific, I can show you 6 dozen different brands and they are all built in similar fashion, and they all fail in similar fashion.
Class D amp design is very similar, it all based on a few companies design work that make and sell the chips and transistors used by ALL brand names.

So the failures appear to be similar in nature, But I have to ask how the system was fused, because I also feel your fusing should have afforded you more protection then it did in this case.

So please understand my questions are based on problem solving, and that starts with the very basic stuff like fuses.

So what size fuses were you running at the amp, and at the battery ???

The damage is done at this point but if you get the amp fixed I would like to think we worked together to prevent such a thing from happening again...

i think u got got confused 1moreamp...this isnt my thread, it's wierdo1's...it's all good though...i was chiming in and asking questions to further my own knowledge based on his/her problem. In my last repy, i was saying that (from the info gather from you b4) that improper fusing "could" have been the origin or at least gateway for the problem. Also, in my first reply, i suggested that the problem prolly originated in the amp due to a faulty part. So now i'm thinking that when the output stage began to go out fusing should have prevented the problem from worsening, however, impoper fusing could have negated that. you reeally seem to know the technical aspects of electrical and hardware function, so i was hoping i could hand you my ignorance and let you turn turn it into knowledge for me

Oh ! I wasn't sure , I was thinking you were getting upset with my line of questioning,,, My Bad

In this case I am thinking several possibilities.

Original output failure, and possible cause might be clipping, and possible voice coil damage which lead to output failure.

Then on restart the output failure had spread to more outputs and the dead short condition "in a Xenon" could have told the amp power supply to run unlimited. BANG big time blow out, and all the smoke goes out to the mighty gods of sound... ..

I hope this info is a little helpful. Most D amps lose a single output, then it spreads to others, and then if not fused or over fused the next weak link is a single fet in the power supply, then there are more fets in the power supply and all that smoke.

I see them all the time, and upon inspection they need ALL the power devices replaced, and the D class driver circuitry is damaged also. Pretty much a total wipe out.
This leads people to think D class amps are poorly designed, when in fact its the huge power inside, and how its utilized that leads to the massive damage.
So I go fuse hunting first thing...


PS I also under fuse my system myself. By this I mean I use fusing that allows me to run my system at the level I want it to, but not by a large margin.
for instance my Xenon 200.4 calls for a 125 amp fuse. I never run it that hard so I run a 80 ampere fuse. Works great and I know the fuse should go way long before a total smoke out takes place, at least thats what I am hoping..

it's funny how the attitude behind text cant be misunderstood. i appreciate the extra time you took to lay it out for me. i actaully do get what you were gettin at this time...i guess i was half right and half wrong with my thinking, but now i actually KNOW more than i did before...thnx for the time and info ....i just noticed that weirdo never chimed back in...must not have found us very helpful

Yeah I guess he found his answer somewhere.

Well if weirdo is not around then I'll just add something from a recent experience.
When I was getting my 4awg power/ground kit from a reputable shop in my area, the guy asks what the amp is rated for and says whatever fuse it's rated for, they [the shop] alway go a bit above. He say "for example, if the amp is rated for 70, then they would put in an 80"
I thought this sounded all wrong and I told him so - that the fuse would not protect because it was too high.

On another point, I happened to go to my regular install shop to get the wires changed (current wire was 8awg) and I told the installer, who said he had 12 years experience, that the manual recommends 2 inline fuses, 1 at the amp and 1 at the battery.
He said he "never heard of such a thing and could not imagine why it would be necessary - either the fuse is going to protect or it's not, so what dif does 2 make?"
Well I couldn't debate the point because I don't know why myself, but I trust you guys (and the manual) more than anybody else so far.

hey guys sorry i was busy working the last little while, the amp was fused at 80 amps but the fuse was ok. the amp at time of problem was not being pushed hard at all maybe 1/4 power, it was running flawlessly along side my xenon 200.4 , then did as i said. the coils on each of the 10" subwoofers all rang out correct when tested with a multimeter, they are type s dual 4 ohm coils are in series and subs are in parallel giving a 4 ohm total load to the amp.. i got the mosfets, took the older ones out but have yet to put the new ones in. still testing the rest of the board for any shorts or anything conspicuous

sounds like a good battle plan...good luck

is there anything common that i should be looking for in these amps

You might have suffered toroid failure. I.E. the windings may have shorted out on one another.

You generally speaking can't test for this, and it will show up again after you rebuild the power supply.

Try and ohm out the outputs. and let me know what your meter reads when you measure them between the leads in any combination.

Also use the resistance range on your meter not the Diode continuity range which is limited to 100 ohms max reading. I have a auto range meter and its always on ohms resistance range when I test...LMK...C

jsut went and measures subs out... the reading for each coil is 3.3 ohms and the total reading is 6.6 - 6.7 very slight fluctuation prolly from meter.. but yea thats the readings from the subs


the output with none of the 8 power mosfets in rings out to 990kohms on the speaker outputs


also i dont know if this is normal but the wire windindgs on the output side of the board are different ohm values acrost eac... one is 19.27 kohms and the other is 0.4ohm.... is this normal..

weirdo wrote: the output with none of the 8 power mosfets in rings out to 990kohms on the speaker outputs

Go the mosfets in the amp section and read the ohms between each pair of the three legs on each Fet. I.e. read from center lead to either leg on left anf then right... You should get no low reading any where, but if there is a bad output there will be a short circuit reading, and that reading will be shared with other Fets even if they are still good. So I use the lifted center lead test next...

also i dont know if this is normal but the wire windindgs on the output side of the board are different ohm values acrost eac... one is 19.27 kohms and the other is 0.4ohm.... is this normal..

Are you talking about the output filter coils located in the D amp section??? Or are you talking about the power toroid in the power supply???

There are inside pics on Amp-guts they can be copied to your desktop and marked with MS paint. Please look at them and copy the one with the area your talking about back here as a attachment.. You might have to use MS picture editor to shrink it to fit on the forum.....C

capitolj80 wrote:i see....bummer...why didnt his amp fuses or inline fuse (assuming he used one) protect the output stage from assault by the external source?...just scrounging for knowledge here

Battery fuse is not meant to protect the amp. It is meant to protect the car.

think of what your CCA is on your battery, this is the cold cranking amps at near freezing after 12 seconds at near 0 ohms resitance and ~12 volts. Think of what wattage your stove top burner is that boils your water. I have seen a 4AWG un-fused cable drop through a floor pan.


The fuse at the amp is not meant to protect the amp either, it is meant to cut off power from the amp in the event it fails, with out power it is less likely to burst into flames.


The circuitry of the amp has built in failure points to protect the amp.

ok theres the pics assuming they load lol the filter coils i believe is what im talking about and i labelled them in the pic and what they were reading...

also teh three mosfets in the amp section and the 3 that iv circled in red are showing a low enough ohm value to set off the continuity in my meter between all the pins to each other. eg left to right, center to right and center to left. each shows a low ohm value not teh same but still enough to set off teh beeper. the ones circled in white are what i have removed atm and have replacements on my deck waiting hope that helps you more if i can provide any more info to your trouble shooting please let me know numbers off of the shorted masfets in teh amp section are IRF640N