First a suggestion: edit the thread title to reflect your question better... “DefTech sub replacement amp help”
(DefTech subs always have issues!)
There was a very recent thread where somebody suggested such a fix for some model of DT Sub... (IIRC it was using a plate amp available through PE) I suspect the cost of repair will be worth more than the value of a repaired sub, though.
I only saw the thread because I follow one of the respondents.