Parasound A23 amp output fused??

I bought a barely used A23 - hooked it up stereo and played it for about 4 hrs - played beautifully. I decided to give it a try on a Hsu Research 10" passive sub (nominally 8 ohm) in bridged mode. Drove it beautifully with authority. I listened for about 2 hrs and shut everything off for the night.
Next morning went to power up and all blue lights on the A23 lit as usual, both channel lights, power light...but no output to the sub! I swapped the sub to an HCA 800II I have and it's working fine. I would assume there's an output fuse of some sort internal but manual says "no user serviceable parts blah, blah". Being a holiday no Parasound help by phone. Any info/thoughts/help would be much appreciated. TIA!