How did I blow my MOSFETs?
I want to make sure this does not happen again, after I replace them.
I had just installed a new EQ, and spliced into the Head Unit's B+/Gnd/REM wires. I didn't do a great job, it was dark, but I didn't think there would be a problem. I went for a test drive afterwards, and near the end of my drive the amp fuse for the subwoofer blew, while the components amp was fine.
When replacing the fuse, I foolishly didn't disconnect the battery, and when placing the fuse (B+ still connected to amp, I tried to just quickly swap it out), I got a ton of sparks. So I unhooked the B+ from amp, and put in the fuse with way less sparks. In hindsight, it seems something was already wrong with the amp by that point. When I went to secure the B+ in the amp I got lots of sparks and burnt electronics smell, very quickly.
So if I replace the MOSFETs, I don't want the same thing to happen. But, i don't know why it happened in the first place. I thought maybe that if the splicing between the HU and the EQ were loose, and then reestablished, then maybe a surge of high voltage overloaded the amp, but, I don't know.
Is it possibly a grounding issue? The higher quality amp blew, while the cheaper one isn't affected. Too many variables to give any ideas?
I want to make sure this does not happen again, after I replace them.
I had just installed a new EQ, and spliced into the Head Unit's B+/Gnd/REM wires. I didn't do a great job, it was dark, but I didn't think there would be a problem. I went for a test drive afterwards, and near the end of my drive the amp fuse for the subwoofer blew, while the components amp was fine.
When replacing the fuse, I foolishly didn't disconnect the battery, and when placing the fuse (B+ still connected to amp, I tried to just quickly swap it out), I got a ton of sparks. So I unhooked the B+ from amp, and put in the fuse with way less sparks. In hindsight, it seems something was already wrong with the amp by that point. When I went to secure the B+ in the amp I got lots of sparks and burnt electronics smell, very quickly.
So if I replace the MOSFETs, I don't want the same thing to happen. But, i don't know why it happened in the first place. I thought maybe that if the splicing between the HU and the EQ were loose, and then reestablished, then maybe a surge of high voltage overloaded the amp, but, I don't know.
Is it possibly a grounding issue? The higher quality amp blew, while the cheaper one isn't affected. Too many variables to give any ideas?
No, car was off - head unit off.
While you're here - I'm confused about the part number for the IRFP064N.
At arrow electronics, they have IRFP064NPBF in stock. Is that the same thing? Since they're N and P...that's no good right?
While you're here - I'm confused about the part number for the IRFP064N.
At arrow electronics, they have IRFP064NPBF in stock. Is that the same thing? Since they're N and P...that's no good right?
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A fault in the amp or a short on the output will kill the mosfets.
A fault in the bias circuit will fry the mosfets.
I would check the bias voltage before connecting a speaker.
A fault in the bias circuit will fry the mosfets.
I would check the bias voltage before connecting a speaker.
With the head unit off (and assuming the amps was off), there's no way for the shorted outputs to cause additional sparking.
I'm assuming that the IRFP064s are for another amp since those are typically power supply FETs and not used in the output stage.
PBF means lead free (Pb is the symbol for lead). Pb Free. Generally, the lead free have the same functionality as the ones containing lead. The lead free are required to pass certain requirements set by various governing bodies (largely those in Europe). Equipment containing parts with lead won't pass the RoHS (restriction on hazardous substances) standards and cannot be imported into some countries (most of Europe and GB).
I'm assuming that the IRFP064s are for another amp since those are typically power supply FETs and not used in the output stage.
PBF means lead free (Pb is the symbol for lead). Pb Free. Generally, the lead free have the same functionality as the ones containing lead. The lead free are required to pass certain requirements set by various governing bodies (largely those in Europe). Equipment containing parts with lead won't pass the RoHS (restriction on hazardous substances) standards and cannot be imported into some countries (most of Europe and GB).
The 064s are for a Fosgate T500-1bdCP. I checked the FETs and they were showing no readings for the ones that smell really bad. I haven't gotten the schematic yet. What would blow the power supply stage?
Looks like I also blew one IRFP3415 :\
Looks like I also blew one IRFP3415 :\
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Don't mix amps in a thread. It's too confusing.
What is the make/model of the amp for the first post?
What is the make/model of the amp for the first post?
I've been speaking of the T500-1bdCP the whole time, as the sub amp. I mentioned another amp for components, to clarify that it was unharmed, and only one amp fried, and I don't know why. Sorry for any confusion 🙂 I thought the IRFP064N were MOSFETS, since they looked like the pictures for TO-247 MOSFETS on Fosgate's website.
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The IRFP064s are FETs (MOSFETS). They are the power supply FETs, not the output FETs.
Please don't try to use terms/descriptions that you don't understand. Ask questions. Please read the entire basic amp repair page (link in sig line below), even the parts that you feel are irrelevant. That will fill in a lot of the gaps.
Please don't try to use terms/descriptions that you don't understand. Ask questions. Please read the entire basic amp repair page (link in sig line below), even the parts that you feel are irrelevant. That will fill in a lot of the gaps.
Okay Perry. So what I've learned is the power supply FETs were destroyed. I am certain this happened when I tried to supply power to the amp after replacing the B+ fuse, due to the immediate smell. The amp had already failed by that point though, and I only made things worse, by taking further action.
I also blew one IRFP3415 on the opposite side of the amp. Is this the input section? My guess is the gain was set too high on the amp for the newly installed EQ outputs, and when trying to adjust the subwoofer level on the EQ, the amp got overloaded, blowing the input stage.
Does this sound right? That, if I blew the FETs on the audio side, the power supply could get damaged if trying to power it up again?
I've got the replacement FETs coming in the mail - but, I'm very afraid of replacing them, but not solving the problem, and damaging the amp further. I have a lot to learn, and RF won't give out the schematic, since the amp is not discontinued.
If both power supply FETs are damaged, what should I check in the circuit that follows them, to see if other parts were damaged as well?
What is my best course of action here? I was just hoping I could easily solder in some new FETs with ease, but that could just be very foolish.
I don't have a power supply to test the amp in home, so I would like to cover my bases, that you think are worth checking, before I put the amp back in the car. From reading your site, it seems I need to see if the voltages are healthy, which can only be done when powered on. So, what can I do, while waiting on these FETs to arrive?
I also blew one IRFP3415 on the opposite side of the amp. Is this the input section? My guess is the gain was set too high on the amp for the newly installed EQ outputs, and when trying to adjust the subwoofer level on the EQ, the amp got overloaded, blowing the input stage.
Does this sound right? That, if I blew the FETs on the audio side, the power supply could get damaged if trying to power it up again?
I've got the replacement FETs coming in the mail - but, I'm very afraid of replacing them, but not solving the problem, and damaging the amp further. I have a lot to learn, and RF won't give out the schematic, since the amp is not discontinued.
If both power supply FETs are damaged, what should I check in the circuit that follows them, to see if other parts were damaged as well?
What is my best course of action here? I was just hoping I could easily solder in some new FETs with ease, but that could just be very foolish.
I don't have a power supply to test the amp in home, so I would like to cover my bases, that you think are worth checking, before I put the amp back in the car. From reading your site, it seems I need to see if the voltages are healthy, which can only be done when powered on. So, what can I do, while waiting on these FETs to arrive?
Who knows what could have been taken out with the amplifier mosfet.
Sometimes nothing and other times a few of the driver components.
You could replace all the faulty mosfets then power up the amp with a current limited power supply or through a bulb. This should limit the current enough to not fry any components. This will give you a powered up amp so you can check voltages and bias voltage.
Sometimes nothing and other times a few of the driver components.
You could replace all the faulty mosfets then power up the amp with a current limited power supply or through a bulb. This should limit the current enough to not fry any components. This will give you a powered up amp so you can check voltages and bias voltage.
How would I power it up through a bulb? I did a quick google search, and was getting irrelevant results.
Put the bulb in series with the positive supply.
If there is a problem the bulb will stay on.
If its OK the bulb will flash briefly then go out.
Okay guys...I am at a complete loss, in every way. Heh.
I repaired the amp today, and I did a great, clean solder job on the through holes. I replaced all the MOSFETs, and tested the amp. All good. I was pretty excited that there were no other problems. I only blew the audio side MOSFETs, then when replacing the fuse, blew the power supply FETs. There were no shorts, all solid connections.
I took a test drive, listening at various volumes, but certainly did not push the amp hard. I'd like to give a run-through of my experience, and hope that someone can tell me WHAT the deal is.
As I said I took a test drive. First I went to the gas station, and fueled up, listening, and very pleased it all worked out. Continued on to drive to store about 10m away, and everything was great from the start. Got to the store, bought some goods, came out, started my car, and immediately the amp caught on fire, as soon as it turned on.
I always turn my volumes down immediately, so it was just the amp turning on with no real power draw, and then a nasty smell. It took me a few seconds to realize what was going on, because I thought the smell was coming from the plastic item I bought in the store.
What gives?? The whole board melted. I just don't understand. I powered the car up several times before that episode, and also ran for 10m beautifully.
This was a refurbished amp from the beginning - I am starting to think it was faulty :\ But I am nowhere near knowledgeable enough to say that with any certainty.
Why would this happen then, and not when I was driving, or when I was testing in the parking lot, etc???
I repaired the amp today, and I did a great, clean solder job on the through holes. I replaced all the MOSFETs, and tested the amp. All good. I was pretty excited that there were no other problems. I only blew the audio side MOSFETs, then when replacing the fuse, blew the power supply FETs. There were no shorts, all solid connections.
I took a test drive, listening at various volumes, but certainly did not push the amp hard. I'd like to give a run-through of my experience, and hope that someone can tell me WHAT the deal is.
As I said I took a test drive. First I went to the gas station, and fueled up, listening, and very pleased it all worked out. Continued on to drive to store about 10m away, and everything was great from the start. Got to the store, bought some goods, came out, started my car, and immediately the amp caught on fire, as soon as it turned on.
I always turn my volumes down immediately, so it was just the amp turning on with no real power draw, and then a nasty smell. It took me a few seconds to realize what was going on, because I thought the smell was coming from the plastic item I bought in the store.
What gives?? The whole board melted. I just don't understand. I powered the car up several times before that episode, and also ran for 10m beautifully.
This was a refurbished amp from the beginning - I am starting to think it was faulty :\ But I am nowhere near knowledgeable enough to say that with any certainty.
Why would this happen then, and not when I was driving, or when I was testing in the parking lot, etc???
Could have been a bad soldered joint that sometimes goes open circuit.
A loose connection somewhere.
The first thing I do when repairing an amp is do a good visual inspection first looking for bad joints or connections.
Perhaps the amp was unstable for some reason and sometimes oscillated and blew itself up.
A loose connection somewhere.
The first thing I do when repairing an amp is do a good visual inspection first looking for bad joints or connections.
Perhaps the amp was unstable for some reason and sometimes oscillated and blew itself up.
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