Yamaha BB424: odd vibration

[AdrianP]

Hi guys. Any idea what might be going on here? My Yamaha BB424 has performed faultlessly for over a year. Just recently,  though, there's been a strange vibration going on. It seems to be coming from the neck and vibrates along with the string being plucked. Any string; open and fretted.

The vibration seems to sound deeper than the lowest note so I thought it might be the truss rod. I've tried tightening it a turn and then loosening it without any effect. It certainly doesn't appear loose when turning it. Ive also tried tightening just about every other screw and bolt on the bass, again, without effect.

So, O wise ones, any idea what it might be?

Thanks.

[AndyTravis]

Machine heads...one of them is loose, they have adjusters on the bottom, and rarely the elephant ear part works loose and may need replacement (although I’ve seen them repaired with blobbed supergluing...)

might not be, but I’d say it’s a possibility 

[TheGreek]

I thought the other end, loose something on the bridge??

[AndyTravis]

6 minutes ago, TheGreek said:

I thought the other end, loose something on the bridge??

Could be. But I know BB’s can suffer this. I have replaced the odd one x

[AdrianP]

Andy. Pity I can't award a like and a thanks at the same time but it looks like you absolutely nailed it! So I turned the bass upside down and looked at the underside of the machine heads. Who knew there were Allen headed adjusters under there? I mean, really! I held onto the elephant ear and gently tightened each adjuster. All were fine except the A string head, which needed about a quarter of a turn before it tightened up. Result? Vibrating sound gone! 

Many thanks.

[AndyTravis]

FYI The plural for a group of BB basses is a ‘Trav’ apparently.

Glad my ‘useless’ knowledge came into play 😉