Lynx Bass (1988) buzzing problem

[Tom Valentine]

I have a perplexing 'buzzing' problem with my 1988 Lynx Bass. Being mainly a guitarist I've never really played it all that much, until recently when a drummer friend asked if I'd like to play some bass in his band, of which I said "Sure, I'll give it a go"

Anyway, here's the problem: The middle position with both pickups selected is relatively quiet, but upon switching to either the rear or front pickup the thing buzzes terribly, I mean LOUD buzzing, enough to be heard over the notes being played.

So I did a copper foil shielding job on the control and pickup cavities, thoroughly soldering all the seams and joining everything together for full electrical continuity, which it does. But I'm still getting a loud buzz using the individual pickups, so I checked the wiring against a published schematic and tested all connections with a multimeter ... everything is wired correctly. Tested the individual pickups and they're both reading a steady 5.xx ohm impedance. No broken grounding from what I can tell ... everything on the ground side shows continuity thruout, from the strings to the output jack and everything in between (including all the copper foil within the various cavities) ... all 'hot' connections similarly show complete continuity, and the pickup selector switch works perfectly. But *still* getting a nasty buzz on the individual pickups.


What could be causing this problem? It isn't my cable or the amp or proximity to the amp, it buzzes *loud* no matter how far I stand from the amp or in what position. When unplugging from the Lynx they're completely quiet, even with a live end on the cable. So what could possibly be causing this within the Lynx?

Thank Ya,
Tommy V

[Elwood]

Just some random thoughts and questions...
Does the buzz change when you touch the strings? If so maybe the ground to the bridge
isn't solid anymore.

Have you tried the same set-up in a different room (on a different circuit)?

I have a laptop power supply that kills radio signals in the bedroom, are
there any suspect power supplies on the same circuit?

elwood

[Tom Valentine]

Thanks for your reply, Ellwood

Just some random thoughts and questions...
Does the buzz change when you touch the strings? If so maybe the ground to the bridge
isn't solid anymore.

Well, yes and no ... after doing the shielding job and still getting the buzzing I tested the bridge and found that it had no ground continuity, so pulled the whole thing out and saw that the ground wire had moved around in the bridge cavity and wasn't making contact anymore. So I put a piece of copper foil into the cavity and soldered the wire to it, then I grinded the bottom of the bridge anchor so that it would make good contact with the copper/solder ... completely full contact now all around. But it didn't solve the buzzing problem.

The buzz does not change when touching the strings, it only happens when using either of the pickups, although the rear pickup is worse ... it almost screetches!

Have you tried the same set-up in a different room (on a different circuit)?

Yes, no difference. In the band rehearsal studio it's going thru an Ampeg SVT-350 w/8-10's ... (awesome sounding setup, BTW ) ... but I run the Ampeg flat with no limiting/compression or other EQ embellishments. At home I'm testing it with a small Peavey Bass amp as well as DI within my DAW computer, which is clean as a whistle. Still, if using any of the individual pickups the thing just buzzes all to heck. Room and setup doesn't seem to be a factor.

I have a laptop power supply that kills radio signals in the bedroom, are
there any suspect power supplies on the same circuit?

Nah, tried that too .... unplugged everything and turned off all florescent lights and such, but still buzzes at the same level. I don't get this same amount of buzzing with any of my electric guitars on the same setup, just with this Lynx Bass. What could possibly be happening here?


~ Tommy V ~

[Elwood]

Hmmm...it sounds like there is a bad ground connection somewhere,
and it wouldn't be a single pickup since things are ok with both and wonky
with both...and the vol and tone seem fine since they work with the middle position,

so...it would have to be the switch(?)... maybe a broken solder joint.

I'd be tempted to temporarily wire each pickup to the jack for a test.
If they sound pretty quiet then you have narrowed things down to the
control plate.

btw...good job on being thorough

[Craig]

Perhaps one or both pickups went microphonic. See: My MFD went massively microphonic! Suggestions?.

Just a thought.

[Tom Valentine]

Thanks, Craig and Elwood, for your replies.

I had a gig last night and didn't want to disassemble anything beforehand .... the gig went well and I kept it in the middle position the entire time. However, during the sound check I experimented a bit and found that the front pickup had some buzzing (at an acceptable level), but the rear pickup was absolutely HUMMING ..... LOUDLY !!! But it still had output of the notes played. This leads me to believe that possibly there is an internal break within the pickup itself, maybe on the negative terminus of the coil ? Would that cause a loud hum while still outputting notes played on the strings?

Craig, would microphonics cause such a thing? Is this a characteristic of when a pickup goes microphonic? I dread having to disassemble the pickup to find out without having some solid evidence that it might be the cause of this problem. Again, I'm getting a steady 5.xx ohm measurement from this pickup so I don't think the internal leads may be broken. However, if it can be pinpointed to microphonics then I'll put on the white lab coat and prepare for surgery.

~ Tommy V ~

(Addendum): A thought --- these pickups are reverse wound or reverse magnetized, yes? If so then that would explain why the middle position cancels the buzzing, but if the rear pickup is the reversed one then all my carefully crafted shielding has just become a great big giant antenna !!!

[Craig]

Thanks, Craig and Elwood, for your replies.

I had a gig last night and didn't want to disassemble anything beforehand .... the gig went well and I kept it in the middle position the entire time. However, during the sound check I experimented a bit and found that the front pickup had some buzzing (at an acceptable level), but the rear pickup was absolutely HUMMING ..... LOUDLY !!! But it still had output of the notes played. This leads me to believe that possibly there is an internal break within the pickup itself, maybe on the negative terminus of the coil ? Would that cause a loud hum while still outputting notes played on the strings?

Craig, would microphonics cause such a thing? Is this a characteristic of when a pickup goes microphonic? I dread having to disassemble the pickup to find out without having some solid evidence that it might be the cause of this problem. Again, I'm getting a steady 5.xx ohm measurement from this pickup so I don't think the internal leads may be broken. However, if it can be pinpointed to microphonics then I'll put on the white lab coat and prepare for surgery.

~ Tommy V ~

(Addendum): A thought --- these pickups are reverse wound or reverse magnetized, yes? If so then that would explain why the middle position cancels the buzzing, but if the rear pickup is the reversed one then all my carefully crafted shielding has just become a great big giant antenna !!!

I only mentioned microphonics because of your description "although the rear pickup is worse ... it almost screetches!".
You might also ask over at Ken Baker's bassesbyleo forum, too.

[bassman]

I am just wondering if you have tried using a different cable to see if there is any difference in this problem?

Unplugging a live cable is not the same thing as it being part of a guitar signal chain. The pickups will act as anntenae and if the cable is unshielded or it has bad shielding, the noise will be worse than the cable unplugged.

All single coil pickups will buzz or hum when solo'd but certain cables seem to make it worse.

[Tom Valentine]

Welp, think I've isolated the buzzing problem within my Lynx bass ...

It seems that one of the polepieces in the rear pickup has gone electrically 'hot' and is making a beeline to the positive side of the circuit. Specifically it's the end polepiece on the G-string, if I touch it with a finger or anything metal it goes "BZZZZZZZZZZZZ" as if touching the tip end of an open cable. Touching any other polepiece on either pickup does not cause this screeching, all other polepiece's are electrically neutral, neither hot nor ground, only this one polepiece exhibits this characteristic.

So I tested each polepiece with an ohm meter with one side connected to the tip of a 10' cable and the other placed on each polepiece in turn ... they all read infinite continuity except this one polepiece which reads 139.6 ohms, essentially a closed circuit. I tried unscrewing and rescrewing the piece several times and even took it out completely, but the internal anchor slug still reads as 'hot' on the meter.

Obviously it's something within the pickup itself ... any thoughts on what might be happening here?

Thanks,
Tommy V



The bottom polepiece of the rear pickup shows
continuity with hot lead of cable (139.6 ohms)





All other polepieces read infinity ohms
('000' alternating with '1000' ... the '1' flashes on my multimeter meaning 'open circuit')

[Elwood]

Well, that's pretty interesting...besides sucking.
Maybe some inner windings lost some insulation from vibrating and aging,
touching or almost that last pole.
I'd get a new one from the G&L store (and use the 10% off that they are offering) .

[Ken Baker]

The pole pieces should be electrically isolated from the signal. Maybe connected to ground, but I don't think so. Based on your findings, it looks like your pickup is in need of repair. With the age of the bass, replacement should be done in pairs so that they are matched.

Having said that:

These are single coil pickups. When both are IN, they should hum cancel each other. However, selecting one pickup will lose the hum canceling and you'll pick up noise from the immediate environment. Think light controls, fluorescent lighting, etc. Just like a Jazz bass.

I don't get over here too often, so if you have more questions about this old beast feel free to stop by across the street at BassesByLeo.

Ken...

[bassman]

I would take out both pickups and inspect all wiring and pickup windings around that G string pole piece. Since G&L pickups have magnets cemented to their bottoms I would look at the glue holding that bridge pickup together as a possible problem area.

I'll bet you find something if you get inside that bass.