NGD - Ground hum issue..

Phantasmagoria

Phantasmagoria

watch where you point that sabre
I just noticed that there's a loud buzz when I touch the bridge pickup (metal) ring on my new Ibby SA. (like touching a live jack tip) This only happens when the bridge pup alone is selected...not even with notch 2 selected on the selector switch (selects/splits one bridge pup coil & the single PU in the middle). It does seem to affect the over-all tone of the bridge pup..especially since I rest my palm on it (pup ring) while playing. I'm not sending the guitar back because I'm pretty sure it's a minor wiring issue that I can fix ...also I'll probably be swapping the stock pup's out some time in the near future anyway (when I can afford new pups haha) ....but meanwhile I'd like to be able to play it without the hum :laugh2:

Anyone have any idea's about what could be causing it? I tried reversing the output jack connections (hot/ground ..in case they were switched by mistake) but it was'nt that. I'm thinking it's probably the bridge pup's ground/hot being reverse wired or something. Anyway..it's a mess in there and I can't really tell what's what lol. The blade switch is also pretty confusing since it's pretty unusual & has terminals on either side of it (?)...kind of like the original switch in my '94 Sabre. (maybe a super switch or something..) Anyway...and help would be greatly appreciated...
 
Re: NGD - Ground hum issue..

I'll try ..but this wiring job makes Metal Maniac's work look amazing haha...
 
Re: NGD - Ground hum issue..

No it sounds pretty much the same and no "clicking"/momentary volume drop while switching either (which often happens when phase is'nt right) ..it's smooth and noiseless...

Overall though, the feel is a bit compressed/"reversed" sounding (don't know how to explain it) lacking attack, like the whole thing was wired "backwards" ..it's not very "open" sounding. I thought maybe the pickups were'nt great, but I think something else is going on with the grounding..
 
Re: NGD - Ground hum issue..

It looks like a candidate for cleaning up the wiring. I notice a few burn marks in there. That suggests it's been worked on. I wonder if it's had any mods/mag swaps ?
Is there grounding to the noisy pup, does it stop humming if you touch the offending pup ?

attachment.php
 
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Re: NGD - Ground hum issue..

No...those burn marks were just me switching the output jack leads :lmao: I've stuck some tape on them now :p

It was bought new and boxed/sealed from an authorized dealer..so I'm the only one who's fiddled with it..

Yeah, I was hoping to avoid rewiring everything (see above :laugh2:) but if I must..then I must...
 
Re: NGD - Ground hum issue..

When I plug the guitar into the amp & touch nothing...its' quiet (maybe a bit of normal/barely audible 60 cycle hum from the single coils)

If I touch the bridge pickup ring it buzzes loudly (like touching a live jack tip)

If I touch any other metal part on the guitar (strings/tuners/bridge etc) while simultaneously touching the noisy pickup ring..the noise immediately drops by about 3/4.

That's what the situation is..
 
Re: NGD - Ground hum issue..

It sounds like there's no grounding to the pup casing and mounting. Alternatively the hot is connected to the casing/mounting inside the pup, instead of ground.
Throw a temp ground wire to the pup ring and see what sound you get.
 
Re: NGD - Ground hum issue..

+1

The grounding path for the metal pickup mounting ring is via the height adjustment screws, then the metal parts of the humbucker, then the pickup's bare screening/ground wire.

This path may have been interrupted or the final connection to ground may be weak or non-existent.

If you try GV's suggestion of a temporary ground wire experiment, it might be acceptable to hold the wire in place with a bandaid sticking plaster. Just do not be daft enough to post pictures of this in any public forum. :D
 
Re: NGD - Ground hum issue..

Yeah, thanks guys ...that worked! It was completely silent when I taped one end of a wire to the volume pot ground and pressed the other end onto the pickup ring with my finger (so my finger was touching it and so was the ground wire). Just guitar noise (seemed like it fattened up and got a bit louder too..) ...no ground noise.. :D

Touching other metal stuff on the guitar (while holding that ground wire in place against the pup ring) made no difference at all as well..so it (guitar) was well grounded.

lol, so how do you guy's think I should go about actually grounding it then? (I can't keep my control cavity open and have a wire dangling over the side of my guitar :p). Should I solder a ground wire to the pickup baseplate and run that to the back of the volume pot? ...or something else?
 
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Re: NGD - Ground hum issue..

Phantasmagoria said:
Yeah, thanks guys ...that worked! It was completely silent when I taped one end of a wire to the volume pot ground and pressed the other end onto the pickup ring with my finger (so my finger was touching it and so was the ground wire). Just guitar noise (seemed like it fattened up and got a bit louder too..) ...no ground noise.. :D

Touching other metal stuff on the guitar (while holding that ground wire in place against the pup ring) made no difference at all as well..so it (guitar) was well grounded.

lol, so how do you guy's think I should go about actually grounding it then? (I can't keep my control cavity open and have a wire dangling over the side of my guitar :p). Should I solder a ground wire to the pickup baseplate and run that to the back of the volume pot? ...or something else?
Click to expand...

I'd look at the pup and see if it has a grounding point/connection to the baseplate and whether it has become disconnected or a cold solder join or something.
There should be a ground wire going to the pup otherwise it wouldn't work.
If that's not a solution try adding a wire like you suggest.
 
Re: NGD - Ground hum issue..

Actually I was looking at the pup and it seems to have rubbed up pretty hard against one side of the ring (looks like an accordion on that side) while being raised/adjusted (not by me). I can also see what looks like mashed wires (green & bare) that seem to have been wrenched in the process..they're almost sticking out of the side of the pup.. I'd be surprised if that's not how something came loose.

I'll have to loosen the strings and unscrew the pup ring/have a closer look...
 
Re: NGD - Ground hum issue..

...all done :)

This is what I meant about the damage at the side of the pup....not sure if you can tell from the pic.

Ibby_bridge_pickup_Damage.jpg





Anyway, I decided not to mess around with pickup surgery etc and just ran a wire from the inside of the pup's leg to the volume pot ground...it works just fine :D

Ibby_ground_wire.jpg



Thanks for the help with this guys :beerchug:
 
Re: NGD - Ground hum issue..

Phantasmagoria said:
...all done :)

This is what I meant about the damage at the side of the pup....not sure if you can tell from the pic.

View attachment 72397





Anyway, I decided not to mess around with pickup surgery etc and just ran a wire from the inside of the pup's leg to the volume pot ground...it works just fine :D

View attachment 72401



Thanks for the help with this guys :beerchug:
Click to expand...

The way this was supposed to work is that the regular input wire has a shield, that shield is soldered to the baseplate inside the pickup, and you need to ground the shield on the other end of the wire inside the pickup cavity.

It is common that people install pickups that have 2 or 4 conductors inside the shield, which gives them signal, but then forgot to ground the shield.

If it's a shield it needs to be grounded.
 
Re: NGD - Ground hum issue..

From what I could tell in the control cavity, the bridge humbucker seems to have (at least lol) 2 (red & white) conductors & a bare (shield) that's grounded at the blade switch (see pics) ..but it still buzzed. I guess the bare (shield) got disconnected at the pickup baseplate end somehow? Anyway running that second wire to ground has completely solved the problem. I left it un-tuned last night 'cause it was late, but I'll tune up and see what it sounds like today (seemed to sound a lot warmer/fatter/louder & more open after I'd finished ...and the buzz had disappeared :D).

This is a "Quantum" (QM) series pickup. They have'nt been around for years. I had those fitted stock on my '94 S-540LTD and they were very usable. Not sure if this one's the same thing, but it's got the same hex poles..except chrome instead of black like the old ones had.
 
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