Unfortuneately that amp is so cheap (can be had for $450 new last time I checked) that you can almost buy a new one for the repair price... Maxxsonics is killing themselves trying to compete with the SPL Comp crowd... That amp should be sold for no less than $600 in my opinion.
The mosfet that has broken off (from vibration, VERY common problem, with all amps like it, not just this model) is an output mosfet. You likely will need to replace all the output mosfets with new matched parts (so it doesn't blow up after 5 mins of use after you repairing it yourself). and you will need to check all the gate and pulldown resistors and replace the mosfet IC's on the output driver board (which have the part numbers rubbed off BTW, AND it requires a $200+ hot air SMD Rework station to do it right). And even then you likely have some power supply FETs and rectifiers that are broken as well and they will ALL need to be replaced with new matching date code parts. Your costs on the parts is double or triple my cost BTW... because we are a fairly high volume repair shop we buy by the hundred, and get much better deals as a result.
Here's your repair quote:
Rebuild output: edited out in case he doesn't want this public
Rebuild Power supply: edited out in case he doesn't want this public
-OR-
Rebuild power supply and Output: edited out in case he doesn't want this public (best deal)
All repair prices include upgraded soldering on the mosfets that is very tedious and requires very hot soldering irons which are very expensive and the technique is not something we will share with any other person/shop. The upgraded soldering will prevent the problem you have had with your amp from ever happening again. This cannot be provided by the factory because it would require hand soldering which as we all know, labor is one of the most expensive parts of building anything, especially "talented" labor. You have to be talented at soldering and have good equipment to do this repair job, no if's and's or but's about it, don't care what anyone else will tell you, we know, we have the experience to back that up.
Would be glad to repair it for you if you decide to repair it. The design in this amp is good, but the power supply transformers are smaller than other amps that use this same design, therefore this amp has a limited power output as compared to say, a Sundown Audio SAZ-3000D, which is the same exact design and parts as this amp, but uses larger, more capable (especially at low ohm loads) transformers in the power supply. Also the SAZ-3000D has a much larger heatsink and the mosfets are not mounted at 90 degrees to the board with spring clips like this amp (inferior), the SAZ-3000D uses screws and bars and the mosfets are mounted at 180 degrees which makes the legs a lot longer on the mosfets which in turn makes it much more capable of absorbing the vibration of 150+dB SPL comp vehicles.
I have rebuilt one of these before, for Maxxsonics. When I took the spring clips off, ALL of the mosfets and rectifiers fell out of the amp onto the floor... LOL.... I told Maxxsonics about it and stressed the reasons they should not use the 90 degree mounting of the mosfets (spring clips really don't matter, the 90 degrees is the problem). The reason that many manufacturers use this method is becuase it allows them to make the amps much smaller so they are easier to mount in a vehicle.... compacted = sell more amps...
Chris
dB-r Electronics
