Well, that. I was told by the owner that it would just cut the signal completely and that wiggling the speaker cable would bring it back. Looking at the solder joints where the jacks are mounted, I could see the cracked solder causing it to cut the sound. As many already know, this is a very common problem with amps with jacks(input/output/speaker/send/return) mounted on PCBs. It’s something simple to fix, but still time consuming. It took more time to take it apart and back together than to dress those solder joints. And there it is, it shouldn’t happen again anytime soon unless someone start yanking at the speaker cable!