How I finally fixed a cracked amp board - steps that actually worked

Did pretty much the same surgery on an old Punch amp a few summers back, except mine cracked up near one of the output inductors and it was intermittent from day one. Took me forever to find it because it only acted up when the sub hit hard and the chassis flexed. Ended up pressing on the board with a plastic pen while it was playing and heard the channel cut in and out, found the crack right there. Instead of a wire jumper I laid down solder along the scraped trace and then a strip of electrical tape over it, wich held fine but your hot glue idea is smarter because tape gets gummy and lifts with heat. Next one I fix is getting glue. The part that bit me was vibration on a longer run. My first attempt used a jumper that looped a bit off the original path and it worked great for a few months untill the hatch area heat cycles loosened one pad and it lifted clean off the board. Had to scrape down to fresh copper and redo the whole thing. Short and following the original path is the whole trick, you nailed it. Still running that amp to this day behind the rear seat of my Silverado. Ugly solder blob and all.

Same deal here with a Blaupunkt I got dirt cheap because it'd cut out on one side. Mine wasn't a crack though, turned out to be a cold joint on one of the RCA input pins. Just reflowed it with a decent iron and it's been solid for two years now. Funny how half these 'broken' amps are just one bad solder joint away from working fine. Did you check your other joints while you were in there? Heat cycles seem to finish off the weak ones eventually.

That hot glue trick is the move, I've been using silicone blobs on mine because they stay rubbery and soak up flex better. One thing I'd add from fixing a Kicker a while back: after you bridge the crack, figure out why it cracked in the first place. Mine was bolted straight to the metal shelf with no give, so every bump flexed the case and worked the board. Threw some rubber grommets under the mounting feet and that was the last repair I ever had to do on it. A jumper just treats the symptom if the mount is still rattling around back there.