Buzzing after shielding

[sham]

Hi guys, hoping you can help me with my guitar setup. I just performed the QTB shielding mod and now I pick up this terrible buzz on my single coils!

I've modded my strat to include a humbucker JB jr in the bridge, and I'm wired up as per this diagram:
i203.photobucket.com/albums/aa11/ajpeagle/Hss%20diagrams/hss-1.jpg
All the ground connections are connected to what I think is called the "star" ground (the terminal ring that's connected to the 400V capacitor).

Anyway, I now get this loud buzzing sound (only on my single coils) that was never there before! When I turn down the tone pot the buzzing disappears. It's not the standard 60hz hum, it sounds very different, it's quite harsh and when I turn down the tone pot I can hear the normal hum underneath. Orientating my guitar in different directions appears to affect the volume of buzzing (this makes me think it's caused by external interference) but it's very hard to remove it completely and not really practical. Touching the exposed metal parts on my guitar doesn't seem to have any effect on the sound.

I'm hoping someone can help. Are there any tests I could do or things I could check to find out what's wrong? Are there any extra things I could try shielding (pickup cables, pickups, something...)? Could my shielding not be good enough? I used the aluminum + spray adhesive method, is there a way to test it? It's irritating because it never happened before I did the QTB mod. The only difference to the QTB mod was that I used a .33uF 275V capacitor instead of a 400V capacitor (it was the highest the shop had..), should that matter? I will try to take some pictures and audio if that will help, I just don't have a camera with me at the moment.

Sorry for the long post and all the questions, but I thought I should try to explain everything. Thanks for any help!

[newey]

Sham-

Hello and Welcome!

I don't have any immediate answers for you. Troubleshooting over the web is difficult. But someone will be along with some suggestions soon.

Did you replace the pots as part of your mod?

The fact that it is directional to some extent does suggest external interference, as you noted. Have you tried it elsewhere? Have you put any new electrical equipment in the room is question since you began your mod?

[D2o]

Hi sham, and allow me to welcome you as well!

Nov 13, 2008 8:57:00 GMT -5 newey said:

I don't have any immediate answers for you. Troubleshooting over the web is difficult.

Yup ... that about sums it up.

But, there is hope. Angelodp was good enough to supply us with some of the best pictures of the QTB that I've seen here.

While his layout is different, it seems to me that he came here because of a similar new buzzing problem, and worked it out by the end of the post. I believe in his case it was partly related to an initial failure to properly insulate the star ground.

Have a look at his excellent pictures at the bottom of this thread, and see if there is anything you missed.

Please post some pictures if you can - that's the best way for us to see what's going on.

D2o

[sham]

Hi newey and D2o

Yes I did replace two of the pots when I did my mod. Switching out the 250k vol and one of the 250k tones for some 500k as per that diagram. The vol pot I used is a push/pull but there is nothing wired to the switches, it's just being used as a standard pot at the moment.

I'll have a read through of that thread by angelodp.

And yes, I understand that troubleshooting long-distance is hard so I appreciate your replies so far Will try to get some pictures up.. might just take a couple of days because I need to borrow a camera.

[newey]

Switching out the 250k vol and one of the 250k tones for some 500k as per that diagram

I thought so. It is possible that the new pot is bad- but that's probably not the most likely culprit, so hold off on that for now, let's have a look at your layout. As D2o notes, a star grounding problem is also possible and probably a more likely scenario.

The vol pot I used is a push/pull but there is nothing wired to the switches, it's just being used as a standard pot at the moment.

I hope "at the moment" means you'll be finding a use for the empty switch lugs soon. Do you have any idea what we do to people who don't use their push/pull pots???

(Just Kidding . . . ;D)

[ChrisK]

Do you have any idea what we do to people who don't use their push/pull pots???

We quietly wish that we too could "just say no."

[sham]

Ok... after a few days of resoldering, lots of testing, and switching to a different wiring scheme the buzzing is gone I think the problem was with the super-switch I was using. Any time I tried a simple wiring scheme using the 4-pole switch I got the buzzing problem. Not sure if it was something I was doing or the switch itself, but doesn't matter changed my wiring plan to one that used my original switch and all is good now.

I even managed to include my push/pull pot into the modified scheme ;D Thanks for all your support and suggestions, helped me through a few scary days where I was worried I had gutted my strat

Here are some (not very good) pics if anyone is interested:
A couple midway through the process...


And some of the finished product