I'm new to 4-track recorders, and have just picked up a Portasound Porta One (1985). I'm now doing a basic test to make sure everything works, but track 1 seems to have an issue. The track 1 meter seems to be registering the input signal OK. So far, so good. But the track 1 signal coming through headphones is barely audible compared to tracks 2, 3, and 4, and equally quiet when I record / play back. I've tried track 2, and that records just fine. I've also tried flipping the tape to check. The track-1 recording is still low volume when played through the track 4 head. Does anyone know what this might be? And is this an easy fix (or perhaps something I've missed - though I can't think what)?.