Neck pickup screeching

[lyonk55]

Hi folks,

I recently picked up a second had 7-string with a Nailbomb set in it and I've been noticing a problem with the neck pickup. When I switch to the neck (or middle positions) I end up with a high-pitched screeching sound that's pretty much impossible to control without turning the volume off, even with a noise gate. The bridge seems fine, just the normal high gain feed back and I've compared to a Miracle Man set in another guitar and that has no problems.

Do you think it's maybe gotten damaged in transit? I know it did get bumped by the courier (I had to re-glue part of the headstock because of it): could that make a pickup microphonic? Is there anything else I can do to diagnose or fix the problem? 

[Dave Sloven]

Courier sounds incompetent!

Now that I've gotten that out of my system, I recommend you checking the pickup mounting first.  I am assuming though that like most humbuckers the mounting is relatively unproblematic, unless it is some special seven-string system.

Also check all the solder joins on the pots and reflow them if you can just to be sure.  Might have broken a cold solder joint

If that all looks okay I am guessing that the knock has loosened the wax potting inside the pickup.

I have heard of a hairdryer and freezer trick that sometimes works but I would wait to see what others say before you go ahead with that.  Anyway that's likely to be hit-and-miss at best.

[Slartibartfarst42]

It certainly sounds like a wax potting problem to me but I'm no expert on this.

[lyonk55]

So if it's a potting issue, what's the best thing to do? I know Bareknuckle will re-pot it if I send it in, but I'm a bit wary of my soldering skills. Would the warranty cover it (I'm assuming not since it's second hand)? I figure if it's not under warranty, it might be easier for me to see if i can find someone who'll do the wiring and potting for me.

[lyonk55]

Actually, another related question.

How thick are the pickup covers? I was looking at the cost of wax potting and saw that it's only a little bit more to add a cover to a pickups (which includes potting it). I usually like the look of covered pickups more, but I'm worried that if I do that they might not fit the routes anymore.

Also: I checked the wiring too. Everything looks in place to me, so I think the problem is the pickup itself.

[Dave Sloven]

I'm pretty sure the warranty only covers the person who originally purchased it.

[gwEm]

you could try setting a low-ish gain tone and tapping the pickup cover. if the tap gets transmitted through to the amp its surely microphonic.

but anyway, i think it has gone microphonic.

i normally pot and repot my own pickups in a wax bath (in fact an old baked bean can), but since you are wary of such things you could give the hair dry trick a go. i've never tried it myself but you just heat the pickup up with a hair dryer and allow it to cool. the problem is the wax takes some time and temperature to actually melt - this will just soften the wax - but it might be enough.

safest option is to take it out and send it to BKP or another tech who can repot it for you.

[Dave Sloven]

With the hair dyer thing don't you also need to pop it into a freezer bag and put it in the freezer for half an hour after it melts?  I think I read somewhere to do that.  That was the wax sets again more quickly. Obviously you don't want to freeze it.

The idea is that if you have bubbles or a crack in the wax this might fix it.  Much more than that and it won't do enough.

[lyonk55]

Yeah, I found the warranty page and looks like it'll cost me. Ah well...

I'll try the tap thing to check it and give the hair dryer a go: not like it's can hurt much, right?

[gwEm]

With the hair dyer thing don't you also need to pop it into a freezer bag and put it in the freezer for half an hour after it melts?  I think I read somewhere to do that.  That was the wax sets again more quickly. Obviously you don't want to freeze it.

The idea is that if you have bubbles or a crack in the wax this might fix it.  Much more than that and it won't do enough.

I've not tried the trick myself, so can't comment. However, I will say that the wax takes a surprisingly long time to melt all the way through - it doesn't conduct heat very well. With using a hair dryer, I'd say you'd only affect the very edges of the wax. However, since these are the areas most likely to have a problem I think it's a decent idea.

For cooling the pickups I usually just leave them out on the table for a while (20 mins or something). I can't see a freezer helping too much, but then I've not tried it as I say, just potted them "conventionally" if you will.

[lyonk55]

Hi guys! I've had a poke at the pickups with a pen and there's definitely a loud ringing coming off the neck one when I do. Just wanted to check though: is it normal to get some sound from tapping the pickups even if they're working correctly? I can clearly hear the tap being amplified on all my guitars, just not as loud and clear as the dodgy one.

[Dave Sloven]

Yes that's normal to get some noise when you tap them.

That's how you test that your pickups are wired in (and not grounded out) when you are installing them, before you fit the strings

[lyonk55]

Fantastic, thanks. Had a look today and I get it done without having to send the pickup away.

Thanks guys!