A few weeks ago the amp in one of my six year old F113V2's died, when turned on just made a "thump, thump, thump..." sound.
I contacted JL Audio and they have a "fixed price" update for out-of-warranty subs, where they not only repair the unit, but they also bring the componentry up to date with the updates they've made over the years.
The JL rep sent me detailed instructions on how to properly remove and reinstall the backplane amplifier.
I am super pleased with the service I received from them, I'd recommend you do the same.