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doughboi916 27th August 2007 03:33 AM

lightning audio amp repair
i need to replace the mosfets on my amp, they are irfz44, i went to radio shack and can only find irf510's, will they work?

Perry Babin 27th August 2007 04:54 AM

The IRF510 is not a suitable substitute.

Get the IRFZ44ZPBF from or

Have you checked for shorted output transistors and other defective components (gate resistors and driver transistors)?

doughboi916 27th August 2007 03:15 PM

i wish i knew how, im new to this, ive been studying,

Perry Babin 27th August 2007 09:30 PM

Can you post a photo of the inside of the amp?

doughboi916 27th August 2007 11:14 PM

here are the guts, sorry, my phone camera is crap

it was wired, i installed it, everything was working fine then all of a sudden i smell some thing burning, pull the REM of the amp and saw smoke, it was wired up rite, the amp does 1000rms @ 1ohm and the woofer was wired to 1 ohm, it was installed in a 300c and there batteries are in the back, i noticed the ground from the (-)BATT to car body looks really thin, like 8ga wire and i have 4ga on the amp.

Perry Babin 27th August 2007 11:33 PM

2 Attachment(s)
Ok, I cleaned up your photo and removed the clamps so you could see the transistors underneath. The 6 transistors on the left are the output transistors. You need to check them with an ohm meter to see if any read anything near zero ohms between any of the legs of any individual transistor. If you have any that read near zero ohms, they're defective.

These amplifiers also have a problem with broken leads on virtually all of the components that are clamped to the heatsink. You need to determine if any have broken leads where the lead goes into the body of the component. Gently push the component to the side. The component will have to be free to move (not clamped, not stuck to the insulator). If the lead is broken internally, the body will move but the lead will not follow. If any of the outputs have broken leads, all 6 should be replaced.

MadMutt 28th August 2007 12:07 AM

Would I be correct in suggesting that a 1ohm load for that amp is a recipe for disaster.
As for it being rated for 1,000w, very obviously a 'marketing' rating.

As such I would be thinking several outputs will also be rather sad.

I Am An Idiot 28th August 2007 01:01 AM

WOW what kind of software did you use to do that Perry?

doughboi916 28th August 2007 03:53 AM

thank you SO!!!!! MUCH for the help, i took the heat sink off and there were 4 transistors that burned up, i will check them with a multimeter, also what could have been the cause? i did notice on a few of the toasted transistors the legs were broken, could that be what made the amp fail? a loose leg touching ground of something??

doughboi916 28th August 2007 03:53 AM

o ya and this line of LA amps are made by Fosgate, real nice quality and were tested to do 1,100 @ 1ohm, also i was wondering if it would make i difference if i put in beefyer FET's? and when i solder new ones in i noticed there was a piece of card board looking thing under the fets, they weren't on the bare aluminum, and there was no thermal past at all, will that help and should i remove the cardboard from under neath the fet's??

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