help with some Left Channel Noise...

Just took delivery of a Sansui AU-9500. Really thrilled. I knew that there was something wrong- the previous owner described a "hiss" in the Left Channel.

That "hiss" is actually more like a low level crackle in the left channel. Unrelated to volume, source or balance. Disappears after around 5 minutes.

Something simple? Worrisome? Common easy fix?