Crackling Audio from Sony SLV-575 VCR
 

On my Sony SLV-575, I have just noticed that the audio has a
crackling sound through both speakers. When trying to adjust
the tracking, it doesn't have the usual range to the left or right before
the sound starts to become noisy and where it then switches to the
linear tracks -- there is simply no range at all - it immediately gets
very much distorted by hitting the tracking button just once or twice.

This happens when playing back tapes recorded on the SLV-575,
and from other VCRs. The problem is primarily with the SP setting.
EP is ok and has somewhat of a tracking range (not quite as much
as another Sony VCR I have).
Does anyone have any experience whether this might be a mechanical
problem (heads?), or whether something on the audio board has gone
south (cap?). Any ideas would be appreciated. -Ken