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Old 19th July 2005, 11:32 AM   #1
jarolda is offline jarolda  Mexico
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Default Problems with an amp

Hello
I have a 2 channel Audiobahn A/B class amplifier (A8002T), I bought it brand new in the US, when I came to my country (Mexico) I connected it and it was working fine until I turned the volume up and there was a short circuit in the system, I checked the fuses and they were blown, I replaced them with new ones and turned it on again, and it happened again, but this time the MOSFET IRFZ44N were blown, This time I replaced them because I tought they were defective and again, the new ones were blown...

I plan to get a new MOSFETS but with a bigger value, like a 70A drain.

Do you think this could be a fix?
The warranty was only valid in the US, that's why I couldn't make it valid.

Thank you
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Old 19th July 2005, 12:19 PM   #2
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Default Problems with amp

I would check the impedance of the speaker system so as not to have this happen again.
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Old 19th July 2005, 12:30 PM   #3
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Replacing with higher current MOSFETs is a bad idea. They have blown again because there is a fault, most probably them blowing in the first place has caused more damage than just the MOSFETs.
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Old 19th July 2005, 07:09 PM   #4
jarolda is offline jarolda  Mexico
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Default Re: Problems with amp

Quote:
Originally posted by stevenbrenner
I would check the impedance of the speaker system so as not to have this happen again.
Yes, I checked the impedance of the sub, nothing wrong with it 4 ohms, that is what the amp says it supports.

Quote:
Originally posted by richie00boy
Replacing with higher current MOSFETs is a bad idea. They have blown again because there is a fault, most probably them blowing in the first place has caused more damage than just the MOSFETs.

I guess I'll just trow it in the trash can, I shouldn't have bought Audiobahn in the first place.

Thank you all
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Old 19th July 2005, 07:43 PM   #5
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Audiobahn isn't that bad. Look to see if any other parts look darkened or burned at all. If you're throwing it away I'll have it! Shame you are so far away.
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Old 19th July 2005, 09:24 PM   #6
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When the MOSFETs die, there ususally isn't much other damage. If there was, it'd be restricted to the totem pole bipolar transistors that drive the MOSFET gates, or the passive components surrounding the MOSFETS.

When you have the MOSFETs short, the amp will blow the fuse as soon as power is applied, regardles of whether the remote is connected, or if it has signal and speakers connected.

WHen you repalce the MOSFETS, id'd just stick in the usual IRF-z44's. Or something with equal or higher ratings. Be sure to replace all of the PSU MOSFETS when you do,

AudiBahn is gnerally considered a middle of the road company. Their amps shouldn't explode. Your sub is the correct rating for the amp. Yo might want to check the sub wiring for shorts to itself or the car chassis. You might also want to check if the amp is overheating - if it runs hot, components are stressed very hard - hook up a computer fan from remote to ground. You should also make sure that the input wiring if of sufficient guage. Sometimes if you have a power power source for the amp and the voltage sags too much, the PSU will try to draw the same wattage which means it will draw more curent and fry (popular failure method of SONY XPLODs). You can measure the voltage at the amp terminals with an ANALOG meter to check for voltage drop while it is playing. The solution is to increase the wire, make sure the connections are good, and maybe get a newer car battery. Farad caps are band-aids. DO you routinely drive the amplifier into clipping? Does the protection on the amp ever engage? It's my goal to install a system so that the protection never activates.
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Old 20th July 2005, 01:08 AM   #7
jarolda is offline jarolda  Mexico
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Quote:
Originally posted by Dr. Photon
When the MOSFETs die, there ususally isn't much other damage. If there was, it'd be restricted to the totem pole bipolar transistors that drive the MOSFET gates, or the passive components surrounding the MOSFETS.

When you have the MOSFETs short, the amp will blow the fuse as soon as power is applied, regardles of whether the remote is connected, or if it has signal and speakers connected.

WHen you repalce the MOSFETS, id'd just stick in the usual IRF-z44's. Or something with equal or higher ratings. Be sure to replace all of the PSU MOSFETS when you do,

AudiBahn is gnerally considered a middle of the road company. Their amps shouldn't explode. Your sub is the correct rating for the amp. Yo might want to check the sub wiring for shorts to itself or the car chassis. You might also want to check if the amp is overheating - if it runs hot, components are stressed very hard - hook up a computer fan from remote to ground. You should also make sure that the input wiring if of sufficient guage. Sometimes if you have a power power source for the amp and the voltage sags too much, the PSU will try to draw the same wattage which means it will draw more curent and fry (popular failure method of SONY XPLODs). You can measure the voltage at the amp terminals with an ANALOG meter to check for voltage drop while it is playing. The solution is to increase the wire, make sure the connections are good, and maybe get a newer car battery. Farad caps are band-aids. DO you routinely drive the amplifier into clipping? Does the protection on the amp ever engage? It's my goal to install a system so that the protection never activates.
Thanks for this good reply, I will check all of those things you mention, I guess I'm running an 4 gauge wire to the battery and this could be a problem, I'll replace it with an 8 gauge size, I'll also check all the connections, and will check for voltage drop, I hope all this work.

Thank you very much!
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Old 20th July 2005, 02:37 AM   #8
Stocker is offline Stocker  United States
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8 is much smaller than 4.

go for 2 or 0 if you must but 4 should be enough for ear-splitting levels before any significant voltage droop.
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Old 20th July 2005, 02:58 AM   #9
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i think the problem of the said amp may not be in the amplifier itself but in the dc to dc converter because the irfz44 was use in that part...so why not isolate the amplifier and supply it with an external +/- supply and test it...if it doesnt cause any trouble then the case is on the mentioned block...i think
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Old 20th July 2005, 07:03 AM   #10
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4 ga should be more than fine. The only weak link in the power deivery system might be a weak alternator or battery (dimming headlights?). The actual amplifier part of the amp should be fine i think.
I would just replace *all* MOSFETS, check to be sure the rest of the parts around them are OK, and then see if it works fine after that.
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