Yeah, so my amp(Carvin SX-100) broke a while ago and i got it fixed at the start of January. The problem was a faulty mosfet causing the volume to die and the amp sounded all muddy. Anyway, Yesterday i turned on my amp, and the EXACT same problem came back. Thing is i had owned it for about 2 and a hhalf years with no problems at all and now its happened twice.

Yeah, so im pretty angry and wondering if anyone has experienced this. I think it may be a problem with the board in it causing it to burn out the mosfet, but it broke 1 month after being fixed.
Actually, does anyone know anything about Mosfet's and if they are all about the same quality because i'll tell them to put an expensive one in to replace it.
I would not tell them to put a high priced mosfet in.

80% chance is there's something else causing that mosfet to burn up. Until you find out what that is I would suggest saving your money on replacement mosfets...

Just my opinion.

Another way to go is sell the amp on eBay for parts/repair and get another amp...
After just one month Carvin should fix that under an "implied warranty", which means that there's no way it should fail after just a month so they should fix it for free. Be sure to give them the entire story so they can diagnose the actual problem rather than just swap out parts.
It's a fine line between clever and stupid.
Well, the amp is never mistreated in anyway at all. It is a 100 watt amp, never turned up past 5 (only happens once a week during jams), and hardly gets used during the week because i use my bro's marshall combo. I think it is a problem in the amp itself thats burning the mosfet out, or the tech did a dodgy job with the replacement.