Sunfire True Sub Junior Problem

[sjdemark]

Hi All,
I'm hoping someone can help me out. I have a Sunfire True Sub Junior than has a blown amp. I scoured the internet but could not find a service manual or scematic anywhere, and Sunfire provides no service support unless you ship the sub back to them for $450.

The original problem was that it would blow one of the rail fuses immediately when plugged in. So without a scematic, I did a little digging on the web and took a shotgun approach. I replaced the output transistors, all 4 mosfets for the downconverter, 2 rectifier ICs, and driver transistors. Most of these components were shorted or open. I also replaced all of the caps. Most of the other components are surface mount. When I fired it back up, it work Ok, but played kind of quite. After a few minutes though, it smelled hot, and sure enough it blew the outputs again.

I've read that when the downconverter mosfets blow it can take out the optocoupler, but this design and amp layout seems quite different from other Sunfire sub amps. I looked at the other ICs and don't even see an optocoupler, just a few opamps.

Can anyone provide a service manual and / or scematic for this sub? Or, can anyone provide advice on where to look next?

Any help would be most appreciated!!!

[sjdemark]

Someone out there must have some experience or information about these subs. Any help would be greatly appreciated!!!

[Chris8sirhC]

That question would be better answered in the amplifiers section. Most people on this board have spent 1/5 as much and built something much better than a sunfire.