Need "Q" Switch Help

[lbpesq]

I added a 3-way "Q" switch to an Alembic Strat pickup set.  I've done this a few times before without any problems.  However it didn't go so smoothly this time.  The "Q" switch seems to be working as it should in the first two positions (0 and 6 db), but is wonky in the third position.  When I switch it to position 3, the guitar squeals.  As I turn the filter clockwise, (1 to 10), the frequency of the squeal gets higher, and counter-clockwise, (10 to 1), makes the squeal lower in pitch.  If I rotate filter back and forth, the squeal rises and falls like an old time radio.  Any help would be greatly appreciated.


Bill, tgo

[paulman]

Throw it through a pitch shifter with some delay, and loop it for ambience during space jams.  Yowsa!

The GD movie with Phil using the film camera EM field noise comes to mind. 

[lbpesq]

Anyone?

Bill, tgo

[rv_bass]

Bill,
I don't have any technical insight, but how about uninstalling and reinstalling the Q-switch.  Maybe there is a problem with the connection.
Rob

[keith_h]

Is something in the cavity accidentally touching the shielding or ground? I recall seeing a similar symptom when folks have had a loose filter pot and the board makes contact with the cavity shielding.

[mica]

You're more than welcome to send in/bring over the filter for testing.

[rv_bass]

Bill,

Was this ever resolved?  I just replaced a 3-position Q-switch in my Series I bass and the same exact thing is happening.  I would appreciate any insight on how to fix it.

Thanks,
Rob

[rv_bass]

Might anybody have any information on the cause and how to fix this issue?  Much appreciated.

Thanks,
Rob

[lbpesq]

Rob, unfortunately I have not yet resolved the problem.  I had a bunch of other stuff to do that put this on the back burner and then I wound up pulling the Alembic guts out of that particular guitar.  I'll deal with it when I finish building another guitar that will be the new home for the Alembic pickups and electronics. 

Bill, tgo

[rv_bass]

Thanks, Bill, I'll let you know if I figure it out first.
Rob

[rv_bass]

Searching the club site I found this:

http://club.alembic.com/index.php?topic=4788.0

Which includes the statement, "The theory is on the corroded jack terminals is that there is micro arcing which is then amplified by your pre amp and then your amplifier."

So, I "exercised" the volume and filter pots, and the q-switches 100 times each, and the problem seems to be resolved for now.  Hopefully corrosion on the pots was the source of the problem.

[edwin]

I had this problem and I had to send the filter back to the mothership for some modifications. Works perfectly ever since. I borrowed the filter from a strat setup for my bass, with a stereo active blend pot. It worked fine in the strat setup, so it must be a situation where the newer preamp modules have something different going on.

[rv_bass]

Thanks for the feedback, Edwin, if it acts up again I will look into sending it in for evaluation.  -Rob

[rv_bass]

This squeal issue has resurfaced, so I’m not sure if it’s a corroded pot issue. I exercised the pots and switches again and the squeal persists when the Q-switch is at the highest setting and the filter is rolled wide open. I’m now wondering if either the switch was installed incorrectly, or there is a compatibility issue with new Q-switches and older Series basses (as Edwin hinted at in a post above). You can see the process and hear the noise at about 2:55 in this video (posted by someone else):


https://m.youtube.com/watch?v=3cHx-cxM2HY

It’s not a big issue, as I can easily avoid the situation that results in the noise, just curious about the actual cause and potential fix.

[Picure]

Searching the club site I found this:

http://club.alembic.com/index.php?topic=4788.0

Which includes the statement, "The theory is on the corroded jack terminals is that there is micro arcing which is then amplified by your pre amp and then your amplifier."

So, I "exercised" the volume and filter pots, and the q-switches 100 times each, and the problem seems to be resolved for now.  Hopefully corrosion on the pots was the source of the problem.

I wonder if putting scilica gel packets in the electronics cavity will help protect the bass from corrosion. Over here in Taiwan is super humid.