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Old 9th March 2010, 05:01 PM   #1
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Default Hifonics goliath

Im working on this amp. The outputs are all toasted in this.

I was looking at the outputs and there are 16 of them total.

15 of them are IRFP360LC and 1 of them is a IRFP460LC.

Are theese pretty much the same part?? Wondering if they are maybe someone fixed this amp before.

So my question is if i put all IRFP360lc's (16 of them) should i be ok?
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Old 9th March 2010, 06:00 PM   #2
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Ahh you got a flea market repair job on your bench. I would say the 460 is not the correct part and someone did a cheapy repair before you, which most likely caused the second failure bringing the amp to your fine bench Mike.

I think the very expensive 360 is the correct part to use in this case, except now you gotta replace them all. Don't you just love those cheap fast repair tech's out there. makes me want to buy a firearm...
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Old 9th March 2010, 06:42 PM   #3
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They are pretty much the same part, I don't like the idea of just replacing one half of the pair though.

IRFP460
500V
20A
Input Cap 4200pF
output Cap 870pF
on resistance of .27 ohm
IRFP360
400V
23A
Input cap 4500pF
Output cap 1100pF
on resistance of .2 ohms
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Old 9th March 2010, 06:51 PM   #4
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The difference between the 360 & 460 is the voltage rating (360 is a 400V Mosfet & 460 is 500V rating), there will be a slight difference in drain source on resistance which will cause the other IRFP360s to possibly carry a tad more current than the 460. I wouldn't expect the whole thing to blow though just because one mosfet happens to be carrying a bit less current than 7 (or 3 if a stereo amp) others

As you are talking about an amplifier output stage switching times simply don't matter as the mosfets will be driven linear from a voltage source.

I guess it's possible that one mosfet out of spec could cause the demise of the others, however i'd describe the amp as miles too close to the edge if this was true

Blowing mosfets in a stable circuit isn't easy if it's designed right & the load is in spec, i'd look at what it was driving. Killing all the fets aint easy & indicates a pretty catastrophic failure. Something tells me there is more to this than just the mosfet/s
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Old 9th March 2010, 07:04 PM   #5
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Mike, I'd suggest that you pass on this repair unless you have 'deep pockets'. These amps can be very difficult to repair and one mistake can lead to the failure of all of the outputs.

If the outputs aren't soldered in place perfectly, the spring clamps may not apply enough force to get the transistors to lay perfectly flat against the sink and the amp will fail the first or second time the amp is driven to full power (at which point, the owner will expect you to repair it again for free.

If the outputs failed, you'll have to replace the driver ICs on the audio driver board.

Did it feel like any of the legs on the power supply FETs were weak when you pulled them away from the heatsink?
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Old 9th March 2010, 11:02 PM   #6
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It didnt feel like any power supply fets were loose however all of the outputs (16) are toasted it blew the fronts off them

Also noticed shaddy solder connections on all outputs and some power supply fets.


1MOREAMP,

Yes it does make me wanna get a gun sometimes I talked to the guy who owns this amp and he said he had it repaired before and it lasted a week.

Perry,

Ive alreadt ripped into this amp so im gonna have to put it back together
I ordered all new outputs ($5.17 each) And you said i have to replace the IC'S also?
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Old 9th March 2010, 11:27 PM   #7
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Yes. If all of the outputs failed, you have to replace all 4 driver ICs. I'd strongly recommend that you use ChipQuik to remove them to prevent damaging the board.

Were any of the legs of the output transistors broken?
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Old 9th March 2010, 11:42 PM   #8
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Yes 2 of the outputs had broken legs on them.

Do you know what ic's there using in this amp since they are defaced
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Old 9th March 2010, 11:49 PM   #9
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If legs were broken, you can expect the legs of the power supply transistors to break soon. The boards don't have enough support and the legs are weakened by vibration. The amp basically commits suicide.

Either the IR21844S or the IRS21844S will work.
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Old 9th March 2010, 11:59 PM   #10
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Perry,

I Talked with someone else about this amp and he said the same thing as you did.

Told me not to mess with the amp .

He said that when maxxsonics designed this amp they did a crap job of designing this amp and i can replace all of the outputs all the power supply fets and put a new output driver board in this amp. And as soon as i hook it up all of my work can go down the drain in 2 secs.


He said they use to long of traces to the gates and the amp has problems with cross conduction.

So im wondering if i should even mess with this or put it back together and tell the guy it cant be fixed.

Any suggestions for me i know you told me not to mess with it should i stick to what you have told me and not attempt to do it?
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