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car amp repair man.....
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<blockquote data-quote="amprepairman" data-source="post: 6582394" data-attributes="member: 618082"><p>to TREY 803....</p><p></p><p>I cant fix a amp over the internet! I can tell you a little about power supplies though..</p><p></p><p>Someone mentioned that the 2 amps posted under my post looked like fet failures...they were right...Virtually all amp failures either start or end with a fet or transistor failure....</p><p></p><p>I allways replace all the fets in a power supply when one fails...In some amps this can get expensive but the past has taught me that its the only reliable way to do it.</p><p></p><p>In the pic Trey posted u'll allso see R40 and R42...those are whats called a "gate resistor" and there should be one for every fet in the power supply..they are usually 10 to 100 ohms but should allways match and be checked in any power supply repair</p><p></p><p>On the fet's....A good manufacturer in my opinion is Intenational Rectifier- on any fet they make they use "IRF" as the beginning of thier part number</p><p></p><p>the IRFZ44 is a very common mosfet found in power supplies usually the 44 will be followed by a alpha character such as a "v" I.E. IRFZ44V and the letter following the 44 does matter its a version number and there are many versions of the Z44...however there are alot of copies out there from various lets say "over seas" companys they will be that companys letters followed by the 44...they seem to self desrtuct pretty easy. The KIA44 is a common one made in korea...its like going to auto zone for car parts...they are ok but not what u want to depend on when ur toolin down the highway at a casual 140 m.p.h....(that was one pissed off cop-he threw me in jail and towed my G.T.A.)</p><p></p><p>If you google IRFZ44 and get on a web site for a IR distributer u'll find a wide array of fets that will fit in the same space as your current ones...(TO-220 case style)higher voltages and higher current capabilities with low on state resistance. This is where a good tech with lots of experience comes in handy...to understand technical data and in my case to have tried a million combinations over the years using my amps as crash test dummies...The same applies to your output section of your amplifier section and doesnt matter if ur running fets or transistor outputs...its just a matter of matching components that will work in your application.</p><p></p><p>Back to the power supply...In the same pic I mentioned before....U'll see a little I.C. surface mounted...It a TI494 TI being Texas Instruments chip designation. That is a pulse width modulator and its the most common one used on the planet earth (there are some aps that run a TI594 which is basically the same but monitors current instead of voltage to regulate the power supply)...anyway...it controls the speed and duty cycle of your power supply (its job is to monitor rail voltages and run faster or slower to keep the rail voltages the same at all times depending on load conditions)...and it can be under the right conditions changed around to give u more power.The changes are external to the chip as far as operating speed and duty cycle which are regulated by a combination of parts that monitor your rail voltages that supply your output transisters or fets...Higher voltage with the ability to carry more current= more power output...and we all know what that is....(in order to get any serious voltage gains a higher voltage transformer must be installed or yours needs to be pulled and rewound so u'll have a fit that looks stock but puts out higher voltage)...one of those old school tricks that guys used to do in low watagge classes.</p><p></p><p>Im not sayin you should start doin mods to your stuff..Im just saying that there are many many options out there that people have been doing for years to give them the edge over the competition</p><p></p><p>So if your gonna try to fix your own power supply issues...First replace ALL the fets....then check ALL the gate resistors and replace any that arent right...At this point things get a little sketchy for the non tech type guys...theres a 50/50 chance its fixed with that but if not...its either one of the transistors that drive the gate resistors called a totem pole driver...or the TI494 itset has cooked or of course you could have a down stream problem...also when mounting new fets make sure you clean up the heatsink very well and get all the little blown up pieces out of it before you remount the new ones allways use new clean heat sink compound and make sure your isolation washers dont have any holes in them(thats the little pieces of plastic between the fets and the heat sink)</p><p></p><p>I could go on and but but Its allready been mentioned that I might post a little to long.....so..thats MosFet 101...</p><p></p><p>The electronics in your amp is just like a chain..when its gonna blow up the weakest link goes first...so if your having the same problem over and over its time to modify it if you really like the amp and want to keep it in your set up.</p><p></p><p>I hope that halps you guys a little....</p></blockquote><p></p>
[QUOTE="amprepairman, post: 6582394, member: 618082"] to TREY 803.... I cant fix a amp over the internet! I can tell you a little about power supplies though.. Someone mentioned that the 2 amps posted under my post looked like fet failures...they were right...Virtually all amp failures either start or end with a fet or transistor failure.... I allways replace all the fets in a power supply when one fails...In some amps this can get expensive but the past has taught me that its the only reliable way to do it. In the pic Trey posted u'll allso see R40 and R42...those are whats called a "gate resistor" and there should be one for every fet in the power supply..they are usually 10 to 100 ohms but should allways match and be checked in any power supply repair On the fet's....A good manufacturer in my opinion is Intenational Rectifier- on any fet they make they use "IRF" as the beginning of thier part number the IRFZ44 is a very common mosfet found in power supplies usually the 44 will be followed by a alpha character such as a "v" I.E. IRFZ44V and the letter following the 44 does matter its a version number and there are many versions of the Z44...however there are alot of copies out there from various lets say "over seas" companys they will be that companys letters followed by the 44...they seem to self desrtuct pretty easy. The KIA44 is a common one made in korea...its like going to auto zone for car parts...they are ok but not what u want to depend on when ur toolin down the highway at a casual 140 m.p.h....(that was one pissed off cop-he threw me in jail and towed my G.T.A.) If you google IRFZ44 and get on a web site for a IR distributer u'll find a wide array of fets that will fit in the same space as your current ones...(TO-220 case style)higher voltages and higher current capabilities with low on state resistance. This is where a good tech with lots of experience comes in handy...to understand technical data and in my case to have tried a million combinations over the years using my amps as crash test dummies...The same applies to your output section of your amplifier section and doesnt matter if ur running fets or transistor outputs...its just a matter of matching components that will work in your application. Back to the power supply...In the same pic I mentioned before....U'll see a little I.C. surface mounted...It a TI494 TI being Texas Instruments chip designation. That is a pulse width modulator and its the most common one used on the planet earth (there are some aps that run a TI594 which is basically the same but monitors current instead of voltage to regulate the power supply)...anyway...it controls the speed and duty cycle of your power supply (its job is to monitor rail voltages and run faster or slower to keep the rail voltages the same at all times depending on load conditions)...and it can be under the right conditions changed around to give u more power.The changes are external to the chip as far as operating speed and duty cycle which are regulated by a combination of parts that monitor your rail voltages that supply your output transisters or fets...Higher voltage with the ability to carry more current= more power output...and we all know what that is....(in order to get any serious voltage gains a higher voltage transformer must be installed or yours needs to be pulled and rewound so u'll have a fit that looks stock but puts out higher voltage)...one of those old school tricks that guys used to do in low watagge classes. Im not sayin you should start doin mods to your stuff..Im just saying that there are many many options out there that people have been doing for years to give them the edge over the competition So if your gonna try to fix your own power supply issues...First replace ALL the fets....then check ALL the gate resistors and replace any that arent right...At this point things get a little sketchy for the non tech type guys...theres a 50/50 chance its fixed with that but if not...its either one of the transistors that drive the gate resistors called a totem pole driver...or the TI494 itset has cooked or of course you could have a down stream problem...also when mounting new fets make sure you clean up the heatsink very well and get all the little blown up pieces out of it before you remount the new ones allways use new clean heat sink compound and make sure your isolation washers dont have any holes in them(thats the little pieces of plastic between the fets and the heat sink) I could go on and but but Its allready been mentioned that I might post a little to long.....so..thats MosFet 101... The electronics in your amp is just like a chain..when its gonna blow up the weakest link goes first...so if your having the same problem over and over its time to modify it if you really like the amp and want to keep it in your set up. I hope that halps you guys a little.... [/QUOTE]
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