Modding HK4000 amplifiers - Visonik & MA Audio

[brtnboarder3241 5,000+ posts]

ty, good thread posted. should be stickied

 

[audioarsonal 10+ year member]

The resistors in the photo I posted are refereing to the "resistor mod" when you change out the 1/4 watt resistors out with 1/2 watt ones. This mod is for the truely hard core HK board owner, and should only be done by someone who's had soldering experience. Or are you talking about wanting a pic of the resistor clipping for the protection removal mod ?

That is what I am looking for.The 1/4 watt resistors.I have done the protection mod already.Just couldn't see clearly from the pics since its kinda small.

As for the relay I was going to suggest you post something about that.It makes a big difference.

 

[snoopdan 5,000+ posts]

The 1/4 resistors are the ones attached to the middle leg of each FET in the output stage. I have a pic around here of it, i'll just have to dig it up and post it //content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gif

 

[audioarsonal 10+ year member]

Sorry to make you dig???Thanks though...//content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[snoopdan 5,000+ posts]

Sorry to make you dig???Thanks though...//content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

hope that helps ? its the resistor to just right of the 3 FET connections. Each FET has a resistor on it, so its pretty evident which ones you need to change out.

 

[dB-r 10+ year member]

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...

 

[dB-r 10+ year member]

In case someone didn't get that, my point was the gate resistors will only burn up when the mosfet fails. Period.

So no need to upgrade them to 1/2 watt types. It is fruitless. While it won't hurt anything, it won't help anything either, just wasting time.

 

[denim 5,000+ posts]

Love the gif. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[Grinder1989 5,000+ posts]

Anyway, too much current passes through the output mosfets, more than they are intended to handle, the mosfet goes bad, becomes a direct short...

Could you upgrade the mosfets? I don't know too much about them but I do know some are better than others.

 

[snoopdan 5,000+ posts]

In case someone didn't get that, my point was the gate resistors will only burn up when the mosfet fails. Period.
So no need to upgrade them to 1/2 watt types. It is fruitless. While it won't hurt anything, it won't help anything either, just wasting time.

Well, I guess my logic behind the 1/4 watt mod is since I was already replacing all of the 1/4 watts at the same time as the IRF9540's anyways, that I might as well put 1/2 watts in there.

 

[dB-r 10+ year member]

They should be IRF9640's, not IRF9540's... wrong parts totally different. IRF9540 handles more current, but less voltage than a IRF9640. As for putting better mosfets in, possibly. I think the IRFB31N20D would be a good replacement possibly for the IRF640, but not sure what to use to replace the IRF9640's as they are P Channel Mosfets and not that popular really, and usually not near as robust as their N-Channel counterparts. IRF640=200V and something like 19-22 amps, whereas the IRF9640 is 200V, but only 11amps... LOL... Just the way it goes. That's why there is usually more IRF9640's than IRF640's in an amp that uses those parts.

If you try to change your outputs in your HK4000D you are doing it at your own risk, the high voltage can kill you and if you use the wrong parts (anything other than the original part) you are likely to blow up your amp or have other weird problems. To use different mosfets you may also have to use different drive circuits and different gate resistors due to different input capacitances of different mosfets. Lots of techno-BS.

 

[Grinder1989 5,000+ posts]

They should be IRF9640's, not IRF9540's... wrong parts totally different. IRF9540 handles more current, but less voltage than a IRF9640. As for putting better mosfets in, possibly. I think the IRFB31N20D would be a good replacement possibly for the IRF640, but not sure what to use to replace the IRF9640's as they are P Channel Mosfets and not that popular really, and usually not near as robust as their N-Channel counterparts. IRF640=200V and something like 19-22 amps, whereas the IRF9640 is 200V, but only 11amps... LOL... Just the way it goes. That's why there is usually more IRF9640's than IRF640's in an amp that uses those parts.
If you try to change your outputs in your HK4000D you are doing it at your own risk, the high voltage can kill you and if you use the wrong parts (anything other than the original part) you are likely to blow up your amp or have other weird problems. To use different mosfets you may also have to use different drive circuits and different gate resistors due to different input capacitances of different mosfets. Lots of techno-BS.

Ah I see. Well I'll own neither of these amps so I don't have to worry about all this lol.

 

[snoopdan 5,000+ posts]

They should be IRF9640's, not IRF9540's... wrong parts totally different. IRF9540 handles more current, but less voltage than a IRF9640.

ah well, it was three years ago when I messed with these amps, im surprised I remember even near what the parts were //content.invisioncic.com/y282845/emoticons/laugh.gif.48439b2acf2cfca21620f01e7f77d1e4.gif

I really really hated owning these amps BTW, were horrible current hogs and was always something werid going on with them. I did however, do some great scores on the termlab with them and one 15" sub so I really cant complain all that much. They just dont last when you drive them beyond the original design //content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gif

 

[lancer1978 10+ year member]

I know this is bumping an old a$$ thread, but does anyone have a diagram of the resistors to cut? Super old school long shot..I found 2, can't find the other 2.

 

[thebestyet218]

I have a M.A. Audio HK4000D and missing parts I have been working on it customized it for awhile now guy I got it from said it had irfp9240 and irfp240 for the output channel transistors was wondering if that is correct parts and the power supply is irfp064N was also wondering if that is correct thanks should have it working again as you can see it does finally power up to 11.4v no problem