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Modding HK4000 amplifiers - Visonik & MA Audio
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<blockquote data-quote="dB-r" data-source="post: 4475059" data-attributes="member: 574699"><p>I believe that resistor is on the first leg of each FET is it a gate resistor, and being that there should not be hardly any voltage drop across it, there is no need for it to be able to dissipate more than 1/4 watt. Heresay at best. Those resistors burn up when the output FETs go bad from passing too much current. So this is how it woud fail:</p><p></p><p>Amp loaded down at .5 or 1 ohm = lots of current passing through each output FET (2nd and 3rd legs, not first leg) Drive signal going into first leg from output driver boards (modules, DLM4500 in this version I believe, there are two different versions of this amp). Anyway, too much current passes through the output mosfets, more than they are intended to handle, the mosfet goes bad, becomes a direct short, various things happen at this point, rail voltage is fed back into the driver board modules (causes them to blow up) and driver board is still trying to drive the mosfet on and off (class D output switching), but since the mosfet has become a dead short, the signal coming from the driver board simply grounds out and the weakest link burns up. The weakest link is either a. circuit board trace b. leg of the mosfet or c. gate resistor. So the gate resistor is the weakest link so it burns up. LOL...</p><p></p><p>HK4000D's and Visoniks are great at 2 ohms. Leave them there, supply good current and you will be happy, and so will the amp. If you need more power and you need it at 1 ohm, get an amp that was built to run at 1 ohm. That's what "I" would do, but what do I know...</p></blockquote><p></p>
[QUOTE="dB-r, post: 4475059, member: 574699"] I believe that resistor is on the first leg of each FET is it a gate resistor, and being that there should not be hardly any voltage drop across it, there is no need for it to be able to dissipate more than 1/4 watt. Heresay at best. Those resistors burn up when the output FETs go bad from passing too much current. So this is how it woud fail: Amp loaded down at .5 or 1 ohm = lots of current passing through each output FET (2nd and 3rd legs, not first leg) Drive signal going into first leg from output driver boards (modules, DLM4500 in this version I believe, there are two different versions of this amp). Anyway, too much current passes through the output mosfets, more than they are intended to handle, the mosfet goes bad, becomes a direct short, various things happen at this point, rail voltage is fed back into the driver board modules (causes them to blow up) and driver board is still trying to drive the mosfet on and off (class D output switching), but since the mosfet has become a dead short, the signal coming from the driver board simply grounds out and the weakest link burns up. The weakest link is either a. circuit board trace b. leg of the mosfet or c. gate resistor. So the gate resistor is the weakest link so it burns up. LOL... HK4000D's and Visoniks are great at 2 ohms. Leave them there, supply good current and you will be happy, and so will the amp. If you need more power and you need it at 1 ohm, get an amp that was built to run at 1 ohm. That's what "I" would do, but what do I know... [/QUOTE]
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Modding HK4000 amplifiers - Visonik & MA Audio
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