4004 truss rod rattles?

[dcr]

Hello! I have a brand new 4004L that is lovely but for one thing. I found that on the E string, the notes produce harsh overtones from about the 5th fret up. These overtones tend to run between C# & D. It sounded like a twisted string to me, but I've tried many different string sets (taking great care to avoid twisting each time) with no change. I have tweaked the rods, the bridge, the pickups, everything, and no difference.

Something I notice now is that when I play those notes unplugged, I can hear a faint but definitely detectable buzzing or rattling sound--it sort of goes "brahrr"--that seems to be emanating from the area of the neck pickup, which is right against the neck. The neck pickup is very secure (as are the 4 screws holding it together), and the noise is there even when the pickup is screwed down tight in the cavity. That leads me to think that the ends of the truss rods, which are right next to the pickup, might be rattling. Also, the pitch of the rattle goes between C# and D, which is EXACTLY the pitch of the harsh overtones that I hear on those frets when I play it amplified. So I think the rattle HAS to be related to the noise that got me tinkering in the first place. (Does that sound plausible?) Incidentally, I find the sustain is dropping off a bit around the C#/D on the G string; also that the rattle/buzz is present on the A string too, although to a much lesser extent than on the E string.

Could this be a rattling truss rod? If so, what should I do about it? The first thought, of course, is to tighten the rods; but the rods are already pretty tight, & in fact the neck is bordering on forward bow already.

By the way, I noticed a similar problem in my trusty old 4003 (split-pickguard era) last summer when I did a string change. At the time I assumed it was just a bad E string in the new set. However, I notice that that bass has the same rattle in the same place, too. Another loose rod?

[jingle_jangle]

Two different types of rods, for starters, Dan...the new 4004 has a "single-action" (tension) rod which bears upon the fretboard from an arced rout, to force the neck convex against the tension of the strings, which want to force it concave. Adjustment keeps the two forces balanced. Unless there is no tension on the rod (unlikely, and not really possible from the factory), there will be no rattling from either end, nor in the center.

The old split-guard has the old-style, bobby-pin style folded-over "single-action" (tension-compression) rod, which causes the lower part of the rod to compress against the upper part, forcing it into a convex curve, which it transfers to the neck. This type rod is out of production, incidentally. It's possible for these to rattle at lower tensions under some conditions.

As to what's causing these overtones, a few minutes with the instrument and a mechanic's stethoscope (available on Ebay for less than 20 bucks) should help to pinpoint the problem area.

[dcr]

Thanks a lot for the reply.

I pulled the strings off the 4004 & removed the pickups. Nothing seemed loose or rattling, & the truss rods (as you predicted) seemed well seated. Yet I still seem to hear something buzzing or rattling, faintly but it's there, & seems strongest around the neck pickup area. And the overtones (usually a C#, sometimes a D) are still there. The E string sounds very different from the rest of the strings, which all sound even & full.

You can hear the overtones here, if you want:
http://www.rickenbacker.com/forum_view_ ... t%20basses
It's the first post, 2nd linked file.

PS One of the truss rod ends didn't have an acorn nut on it, only a hex nut. Does that matter? (Probably not.) I wasn't able to push it through to look at the end more closely.

[dcr]

I cannot track down anything that's actually loose or buzzing. Maybe this is really simple: every instrument tends to get "excited" at certain frequencies, and when you hit that frequency with high-mass strings, things "hum" a bit, faintly, if you really get close. I notice this on other instruments too. Perhaps that's all that's going on here?

[johnallg]

Dan, you could pull the rod and see if it has the masking tape on it that helps reduce rattle, or if that tape is torn and causing the sound you hear.