Double Bass Underwood crackle

[Jay Mendoza]

6 months got a new bridge, and had the luthier install my Underwood, he did a great job and the elements are a perfect fit in the wings; snug but not compressed and can be moved easily. I test drove it on one of the bass amps at the shop and was pleased.

I never had the chance to play it plugged in again until last week, and noticed a crackling sound which I determined was from the bass side element, as it went away when I removed it. The elements have not been over compressed as the black silicon potting material is still concave and not being squished out. They are still a loose fit in the wings too. I removed the pick-up before having the strings changed. I pulled back the heat shrink at the element, and the cable solder joint and braid are good and not damaged in any way. Wondering what could have happened?

 

[Francois Blais]

I'm afraid the bass element is dying.
I had one dying the same way a few months ago.
You can get in touch with the Underwoods to see if they'd replace it, but you can also cut the cable right after the treble element, and then place it in the bass wing.

 

[DoubleMIDI]

The silicon is only a filler at the edges.
There is a thick ceramic disk between the brass plates, one side of the disk isolated and connected to the hot wire, the brass housing connected to the shield.

I once (maybe twice) had the shield broken where it was soldered to the brass housing on a Shadow SH-950 (the prototype). It sometimes worked sometimes not and produced noise.
It was only visible after bending the brass around the cable (behind the shrinking tube) open.
Be very careful not to stress the hot wire connection because you might not be able to resolder it if it gets broken.

But before you open it, first inspect the jack if the cable is still connected as it should.

If the piezo ceramic disk is broken (by hard pressure or impact) you cannot repair it. Cutting off the cable to get a single element pickup would be the best idea then.

You can ask for a replacement (maybe with a discount on the regular price) before you cut the element off, but what I can remember is that they don‘t do that any longer.