Pickup screws causing microphonics with Bartolini 9SU's

[JustForSport]

If the screws are actually moving a small amount, wrap a bit of plastic 'baggy' around the screws (not to make it too tight) and then insert the screws. This will keep the screws from wiggling in the magnetic field and from vibrating against the housing. If it does not improve things, it could then be the pickup mounting tension.

 

[BobaMosfett]

Well, when we covered the top part of the screws with tape, so it is not directly touching any part of the pickup, the problem is far less.

At some point, I will try to obtain some brass screws, to see if this helps too. For now, the bass seems usable again, although I haven't tried it in a live setting yet.

I started this thread mostly to find out if this is a known problem with these pickups, or that I'm just having bad luck with these two pairs, these screws, this bass or any combination of the factors. So if anyone uses Bartolini 9SU's please let me know!

Anyway, thanks for your responses so far.

 

[Bruce Johnson]

I still think that you are misunderstanding what's happening. The problem isn't that the screws are wiggling. They are screwed into the body. What's happening is that the whole pickup is wiggling on the screws, in relation to the body. Meanwhile, the strings are sitting still. This movement of the pickup in relation to the strings is what is creating the microphonic signal. It's almost like the strings moving above the pickup, like normal operation, but reversed. The screws themselves are far enough outside of the pickup's magnetic field, that they aren't going to create signal. Changing the screws to brass isn't going to do anything. Unless the brass screws fit better.....

Now, if you wrap tape around the shank of the screws, so that you are filling the gap between the screw shank and the hole through the pickup, that will do something. That will help keep the pickup from wiggling. But the better fix is to add a foam pad or better springs under the pickup, to push it up against the screw heads, and prevent it from wiggling and wobbling.

 

[BobaMosfett]

No, I don't think that's what's happening.
While the bass was lying on the bench, the pickups were soldered and put in the body (without the screws!). The strings were nowhere near them. No microphonic behavior when tapping or scraping them. Shoving the screws through the holes already produced noise, and when they were screwed in place, tapping and scraping the pickups was very audible through the amp. Still without the strings!

So then we had the idea to tape the screws, wich helped.

By the way, tapping the pickups outside the body with a screw was also very audible.

 

[chaosmic]

I've got the EXACT same issue with the Bartolini single-coil Jazz pickups in my 5-string Roscoe. If I touch certain mounting screws (some don't seem to have the problem) it's literally like touching a hot microphone.

 

[JustForSport]

Did you try tapping the pickups outside the body with a chopstick or something wooden?
Since epoxy can be pretty thick, 'specially when it starts to set up, maybe that batch didn't get far into the winding, but set up after just covering the top.
That would still leave the windings not potted, really- and no way to see from the exterior.

 

[megafiddle]

I still think that you are misunderstanding what's happening. The problem isn't that the screws are wiggling. They are screwed into the body. What's happening is that the whole pickup is wiggling on the screws, in relation to the body. Meanwhile, the strings are sitting still. This movement of the pickup in relation to the strings is what is creating the microphonic signal. It's almost like the strings moving above the pickup, like normal operation, but reversed. The screws themselves are far enough outside of the pickup's magnetic field, that they aren't going to create signal. Changing the screws to brass isn't going to do anything. Unless the brass screws fit better.....
Now, if you wrap tape around the shank of the screws, so that you are filling the gap between the screw shank and the hole through the pickup, that will do something. That will help keep the pickup from wiggling. But the better fix is to add a foam pad or better springs under the pickup, to push it up against the screw heads, and prevent it from wiggling and wobbling.

Good point. It's the relative movement that's the source of the problem.
More importantly though, even though the strings were not involved, they will be eventually.
Even with brass (nonmagnetic) screws, the pickup needs to be immobilized.

I've got the EXACT same issue with the Bartolini single-coil Jazz pickups in my 5-string Roscoe. If I touch certain mounting screws (some don't seem to have the problem) it's literally like touching a hot microphone.

According to Bartolini
Invalid Link Removed
"We drill the mounting holes after we finish the epoxy process"
Sounds like they drilled just a bit to close to the coil.
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