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Im freaking out. Ill lay it out. Im running a pos deck decent rca's into a rockford 5x crossover to a pld line driver and into the amp. Its powerd with 0awg into a 100 amp fuse. Its powering a single dragster 12" (winter beater sub) About 2 weeks ago i notice the amp kicks into protection, i figure oops too much pounding so i shut it down, and fire it back up... no problems. Everything is fine untill i turn it up again (2-3 days later) and it goes into protection. So now i get annoyed because it starts doing it alot, even at low volume. I pulled the amp out and open it up looking for the obvious (Im first year electrical) a burnt resistor, bad wire somewhere, a hot spot all the easy stuff i cant find anything. I pulled the board off the heat sink and when i turn the amp on the things that contact the heat sink (not sure what they are) get hot. As soon as i turn it up they get too hot and it goes into protection. I need to fix this amp anyone with any ideas please let me know
posted
u shouldnt turn the amp up with the board off the heatsink, because of overheating easyly. what is getting hot is the mosfets. try another sub could be a bad coil...SPLaudio
Posts: 6887 | From: north rose,ny | Registered: Aug 2002
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posted
those little things on the board are called transistors and rectifiers. they get extremely hot, hince the term "heat sink." they don't teach you that stuff in electrical school or is it electronics school. prolly not electrical, they just teach you ohms law and then teach you how to pull wire, and run conduits(went through two years of being an electrician) although if you are lucky you can swipe some mcm 750 wire!!! anywho, the amp can easily be fixed, on the board see exactly what is blown, you should have the transistors being irf744s or irf540s, those are n channels and most of the time thats what is fried in amps. fixing amps its easy, all you really need is a multimeter with continuity, although expensive tools can help with bad blows. my going rate usually starts at $100 to fix an amp, if you live in canada or afghanistan, its gonna cost you more for shipping, and $50 more if you speak french.
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I get a decent electronics course to go with my electrical. I took the amp in for an estimate and the guy told me "the transistors are probably fried, you have to take them off the board to test em and if theres one gone you might as well switch em all and there $15 each so 20 (10 per channel) is $300 and labor". The guy also said that you can use an ohm meter or diode check to test them. My teacher says that you cant use a meter and instead i have to build a simple circuit (3 resistors), plug the "mosfet" "transistor" "rectifier" and measure the current. I have been testing and measuring current for like hour and have yet to have one work like i was informed. Anyway if there is a real and good way of testing these id love to know... also there are two diffenfent types ( irfz44 and irfz46) in one channel (5 of each) where the other channel has 10 of the same irfz 46 anyway my question is are the IRFZ 44's the same as the IRFZ 46??
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Ok let me rephrase... are the IRFZ 44's going to function the same as the 46's? BTW is that $100 parts included? and non je ne parle pas francais.
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$15-20 per transistor, the guy is playing you for a punk. off digikey irfz44s are $1.80 and the p channels do that shouldn't be more than .20 more. you would be better off going with sergey klypin or myself. i don't want to see you spend $300, may as well sell yours and buy a new one. npn and pnp should be changed out, not all n channels and p channels. but seriously, this guy is no good, he may get the job done, but he is way overcharging you. also you could check out http://caraudio-repairs.com, he is an extremely good friend of mine, used to work for dei before he moved to florida.
one thing that i would check is the rectifiers first cause if it is playing fine till you get to a certain point of current draw then you may bee getting some leakage due too heat fade but that is where i would start
and right off check the coil on your sub and see if the impedence hasnt risen any this could be a culprit also
start with the external basics first could be somthin simple
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i was just gonna poke her in the pooper Posts: 2415 | From: tulsa, oklahoma | Registered: Jan 2003
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Dude - had Jarfunkz not already replied, I would have directed you to his corner of the States. Don't think he'd stear you wrong - had I the cash a few years ago, he would have received a couple HCCAs from me (drool alone couldn't buy them - dang!!).
Good luck & excellent amp!! Nice to see an AA floating around out there .
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Anyway if i cant fix it i will ship it out. My original questions still stand "are the IRFZ 44's going to function the same as the 46's?" and how do I test these things . Oh yes and are these MOSFETs? If so what kind are they? Im new to electronics but im not incapable of handling this.
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JEEZ, IF I TOLD YOU HOW TO TEST TRANSISTORS I WOULD BE OUT OF A JOB, THIS IS HOW SOME OF US MAKE OUR MONEY, SO BASICALLY YOU ARE ASKING ME TO FIX YOUR AMP FOR FREE... IF YOU NEED TO REPLACE 44'S REPLACE 44'S WITH 44'S, IF YOU NEED TO REPLACE 46'S WITH 46'S REPLACE 46'S.
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