Middle position hum

[Mitch T]

Hi guys, thought I'd ask here.
After swapping pickups and pots and a pretty good shielding job on both cavity and pickguard. Now I have a slight, but annoying hum in the middle position.
Pickups are RWRP. For the rest everything is perfect.
I must say the solder blob, sporting the grounding wire from the three position switch to ground (I used the tone pot and star grounding) was quite a bulky one. Could it be that blob is making electrical connections where they shouldn't be?

[ChrisDesign]

Is the solder dull? If so it’s a cold joint that needs resoldering.

Is your shielding grounded?

[DrPete]

Hi guys, thought I'd ask here.
After swapping pickups and pots and a pretty good shielding job on both cavity and pickguard. Now I have a slight, but annoying hum in the middle position.
Pickups are RWRP. For the rest everything is perfect.
I must say the solder blob, sporting the grounding wire from the three position switch to ground (I used the tone pot and star grounding) was quite a bulky one. Could it be that blob is making electrical connections where they shouldn't be?

This happened to me after soldering in a set of Vintage 65s to my Japanese Jazzmaster last year. The hum was awful at every position! It was my first time soldering so I just had to re-solder everything again and it was all good!

[Mitch T]

Shielding is grounded. All solder is slightly dull looking since RoHS
I have my doubts about that one, will redo it.

I've done some more tests: without strings, there is only hum in positions 1 and 3. Middle position is much quieter but with a higher pitched hum. Call it a sizzle.
Then I recalled that both at home (ungrounded outlets) and in our rehearsal space (big machines and lighting on same group) electricity is not very "clean".
I think I'm picking up RF but I use a total pickguard shield and shielded the entire cavity with aluminum tape...

[timtam]

Jumper each pickup direct to the guitar cable. That will tell you how noisy each pickup is on its own. If each isolated pickup is quieter than when wired in place, there's something in your wiring that is contributing to the noise. But the fact that the middle RWRP is reducing the noise suggests that it may be just each pickup's inherent noise susceptibility (to environmental EMR) that you're hearing (when not in parallel RWRP). Tom Bukovac only uses his JM in the middle RWRP position for that reason ... noise comparison ...
https://youtu.be/aWaL48JqppQ?&t=283