hifi engine

AIWA SA-C22 makes BUZZING sound


I have a AIWA Stereo Preamplifier C22 that makes buzzing sound once in a while.

When a give it a little tap it stops or get worse.

I guess it can be a grounding problem. I have taken it apart and it doesen´t seems to be any loose parts.

Any idea?

/Best regards, "Mattan"