MA AUDIO HK401SX

[mike49504]

Got this amp in for repair . On the power supply fets i get the following voltages.

1:5.38
2:13.89
3:3.71

Defective ?

[Perry Babin]

Bad ground. The 3rd leg should be at 0v.

[mike49504]

Do you know what they use for fets in this amp? Someone got crazy with the soldering gun and put different fets in this amp also after i removed the clamps half of them arent even soldered in the board . Irfz44's are whats in the amp now with 68 ohm gate resistors.

Will the 44's work or do i need to replace them with different fets?

[Perry Babin]

The Z44s won't cause a problem but I don't know if they'll be reliable because I have no experience with this amp.

[mike49504]

Ok i forgot i had a scrap board laying around out of another MA amp thats the same power and Z44's were used in that amp so I should be good.

So now off to rebuild the power supply

[mike49504]

Can i use the IRFZ46's in this amp and still use the 68 ohm resistors?

[Perry Babin]

That should be OK.

[mike49504]

Ok i replaced the power supply fets and gate resistors . Amp works 100%

[way2eazy]

Originally Posted by mike49504

Ok i replaced the power supply fets and gate resistors . Amp works 100%

mike49504 i see u have tested the amp and now it works 100%.....i see u dont have alot of experince fixing ma audio amps. so my question is have u seen anyone using that amp (401sx) to its full potential? because i wanna run two of those amps. i had one previously and like it but i only had it a 4ohms and it was only one sub. any help would be appreciated. sorry if i "thread jack not intentional"

[mike49504]

I have fixed several MA amps along with alot of other brands Just dont know what the correct parts are sometimes when someone gets into them and trys to fix them and they dont have the first clue on what they are doing.

Ive heard 1 of theese amps and its a pretty powerful amp i was surprized what the amp could do very clean and powerful.