Repair of  2 Mackie SWA 1501 Sub Amplifiers


Fault -  both dead   

The Mackie SWA 1501 Sub Amplifier  is a quite complex circuit involving a type of switching  PSU a class H Bi Polar output stage combined with a  FET output stage,( the Americans refer to class H as class G - see literature on this amplifier) it is overly complex in my opinion, these type of amplifiers are not necessarily the most reliable, or the best sound quality, but they are a cheap route  to making a high power amplifier, using conventional circuit architecture would be a lot more expensive to produce, after all what fun it is making something more complex than it actually needs to be, the highly paid Mackie design department have to justify their wages ! 

The Customer dropped off just the 2 amplifier chassis.

This was the first one which had quite obviously gone bang with multiple blown components, but both units had pretty much the same problems - not quite identical, but  it does seem that these type of amplifiers always blow the bipolar transistors and mosfets in the output stage also taking out associated diodes, resistors and transistors etc. If I was in charge of the Mackie design department, I probably would have said - guys what were you thinking !   

PCB of one of the amplifiers after the repair had been completed 

The 2 amplifier chassis after the repair ready to go 


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