Shielding hum on a Precision...

[KK Jale]

It's a funny thing. I've got two Precisions here, a 62 reissue and a 57, but one has much worse shielding hum than the other, and I'm struggling to understand why.

Both basses are near-identical Japanese Squiers from 1982. Same pickups, same pots, same everything, with grounding plates in the pickup cavity and earth wires from under the bridge running back to a pot casing. However, but the 62 reissue hums MUCH more than the 57 (when you're not touching the strings, of course - then they're both fine).

One difference between the two is that the 57 has an anodised aluminium guard… but it's not soldered to ground so in theory IFAIK it shouldn't make a difference. In fact today I just backed the '62's guard with aluminium foil, not grounded yet, and it made no difference either, so that should prove it.

BTW, I've been through both basses with an ohmmeter checking resistance between output jack ground and various points, and both check out almost identically.

Before you say "The 62's pickup is dodgy" - well, I just swapped in a Lollar. Superb pickup! But still the same shielding hum difference.

I really want to improve the 62 to be as good as the 57.... but before I set to work, I wish I knew WHY the 57 is naturally so much better...

Any ideas most welcome.

[Ou7shined]

Do they both have identical value capacitors?
I'm as flummoxed as you but thinking outside the box perhaps they both hum, only one bleeds off more highs (where the hums tend to sit) which makes it appear to not hum.
I'm sleepy, does that make sense?

[KK Jale]

Yep! Same value little green caps. Good sleepy thinking though!