The other day, my subwoofer suddenly cut out and I traced the issue to my subwoofer pre-outs on my Kenwood DDX-319 head unit.
Troubleshooting done so far:
No AC voltage comes out of the subwoofer pre-outs on the head unit at all
Connecting the sub amp's RCAs to the rear pre-out produces sound from the sub (ruling out that it is my amp or subwoofer)
There is no resistance (0 ohms) between my pre-out grounds and the case of the head unit (leading me to believe it is not simply a blown fuse in the head unit)
Everything else on the head unit functions as intended
My head unit is out of warranty by a couple months. I emailed Kenwood about the problem, but they will most likely give me the run-around and ask a million questions before giving me a repair quote that I expect to be at least $100, something I can't really afford right now with a new semester starting. I have some proficiency in electronics (enough to most likely be able to replace a broken component, if I can tell that it's broken), so I'll probably end up opening the head unit and seeing what I can do. I have never used the amp in the head unit, so it's unlikely that it's a heat-induced malfunction, in my eyes.
Any help I can get is appreciated, especially things that would help me repair the head unit, like what components could possibly be broken.
Thanks!