Tips for installing covers

[shawnl]

I've been hitting up this forum pretty hard lately and hope I don't appear helpless but I get very valuable information from you guys. So here's a big thanks to all you veteran winders who take time to help out novices like myself.

After many experiments, i'm getting very close to finalizing a pickup set I'm going to use in my next bass. I'm going to be using custom made wooden covers and I'm trying to find the best way of installing them on a single coil with an exposed blade pole. The cover obviously has an opening to allow the blade pole to poke through. If I turn the cover top facing down, drop in the pickup and fill the existing space with potting wax, is this all that is needed to keep the pickup in place? How do you guys mount pickups that don't have a baseplate? Or if you do use a baseplate, how do you fasten the pickup to the baseplate if it's a blade pole and you can't run screws through center? Is the magnetic force enough to hold in place?

[David King]

Don't use potting wax, it will seep into your unfinished wooden covers and make a mess. It will also shrink dramatically as it cools and could tear up the pickup's outer windings. Use a hot glue gun to tack the back of the PU bobbin to the edges of the back of your cover assuming they are adjacent with no wide gap. Don't over do it -just enough to keep the thing together, that's all.
You could also use a strip of Gaffers tape across the back. Get the real cloth stuff at $20/roll not the fake stuff which is just black duct tape. The latter will age badly and gum up everything.

[shawnl]

Thanks David,

I'm just a little curious though, I've seen pickups in google searches that seem to be completely encased in wax. Were these by chance potted after they had the covers installed or I am mistaking the wax for something else?

[David King]

Shawnl,
There are investment casting waxes that don't shrink when they cool ($$). More likely what you saw was potting epoxy -not wax.

[rjb]

Were these by chance potted after they had the covers installed or I am mistaking the wax for something else?

Some (eg. DiMarzio Model P) use hot glue that might look like wax.

[David Schwab]

Thanks David,

I'm just a little curious though, I've seen pickups in google searches that seem to be completely encased in wax. Were these by chance potted after they had the covers installed or I am mistaking the wax for something else?

Most pickups like this are encapsulated in epoxy, not wax. No one uses wax.

[David King]

Epoxy isn't reversible for obvious reasons. Traditionally guitar HBs have enough wax in the cover to keep them from squealing at high volumes. So while not encased, wax is used to dampen the covers.

[David Schwab]

Epoxy isn't reversible for obvious reasons. Traditionally guitar HBs have enough wax in the cover to keep them from squealing at high volumes. So while not encased, wax is used to dampen the covers.

He's making bass pickups in wooden covers. No one fills those with wax. With guitar humbuckers with metal covers, you should just have enough wax in the top of the cover to stop them from vibrating. You certainly don't fill the cover with wax.

On a typical soapbar bass pickup, there is nothing to hold the pickup inside the cover. So they are encapsulated with epoxy. That also stops them from being microphonic and squealing, which just potting them in wax will not do. I know this from experience, as some of my pickups in my personal basses are not epoxy encapsulated, and they will squeal when I get too close to my amp. Happened just last night in a rehearsal studio.

Obviously test the pickup out first to make sure you like the tone. Make as many changes as needed, and then when the design is finalized, pot it with epoxy.

The blades are going to have to be a snug fit to stop the epoxy from leaking out the slots. An alternative is to seat the blades into the slots with some 5 minute epoxy to seal up the openings. Any squeeze out can be cleaned up with rubbing alcohol before it sets.

[soundguruman]

Lots of builders use wax, including Gibson.
I just recovered a brand new Angus Young with a gold cover...
The wax is applied very lightly, on top on the bobbin, only around the pole screw holes, so that the airspace is sealed.
A small amount is used around the seam, between the base and the cover.
Over-waxing kills the tone, and does not accomplish much. They (Gibson) double wax the bobbins, (on Angus model) but very lightly applied.
No, it's not epoxy, it's wax. Stock, From the Gibson Factory. Open it up and look for yourself.
Since I like Gibson humbucker better than any of the rest, I just needed a gold cover instead of chrome. I used Seymour custom shop cover, which
I thought was much better quality than any Chinese I looked at.
And the Angus PU, whoa! I love it. I mean this thing screams harmonics and overtones, but has essentially NO squealing feedback or hum, noise. The best one I have ever tried, period. (I have tried a crap load of pickups! This one takes the prize.) OK so if you buy a $300 pickup, you get what you paid for.



You can see where the wax was applied, just around the pole screw holes, and around the seam, between the base and the cover.
Very lightly, and nowhere else...
This is highly effective in dampening the microphonics of the PU. I mean, it worked really good.

HERE is some more notes on the subject, written by KK: (he is speaking the pigeon English, but if you read carefully, you will get some good info...)
what i meant was, if you have taken the cover off of modern post 1990 double dipped gibson pickups. they are different from pre 1990 which is non potted. you see, as i explained before purists dont want potted pickups. gibson hanged in there till 1990 but they finally had to create their potting method and wax. you will see what i'm talking about when you take the cover off of your angus. it is pretty messy undernieth unlike older and seymours. if you use wax which is too soft, it will kill the sensitivity. but if wax is too hard like c-a glue, it will still squeel. so this potting method and wax material is trader's secret. seymore don't dip as much as gibson to keep the sensitivity high. it all depends on the volume level you are playing at. purists who use those small 50s and 60s combo amps wants their sensitivity set at max= non pot. full stack needs potted pickup. i think seymour use some kind of vaccume chamber to draw out all the remaining air inside of windings. he mainly pot bobbins, rest very light. pickup experts only take winding from neck side bobbin to create un-match at their suitable off set point. you can balance the colis to reduce noise to maximum, but it won't become what guitarists would call good sounding. purist who still believe late 50s patent appried for pickup is the best usually start their re-productions at 5000 and 4900 turns. yeah, get the gold poles from joe.
un waxed un treated cover's top tend to oscilate. try tap the brand new cover, it will go teeeen, teeeeeeen.

gibson dip the bobbins before taping first, then they assemble the pickup, put cover on then they dip it again=double dipped. so the wax is filling the space between top on the bobbin and underside of the cover.

vaccum is potting method and there is no vaccum area in pickup.

so basically gibson want as much as wax remain under the cover. they heat gun off excess out side and bottom to make pickup look nice and clean.

[David Schwab]

Lots of builders use wax, including Gibson.

We are not talking about wax potting the coil, etc.

We are talking about this:



While what you said is true for a Gibson style humbucker with a metal cover, that wasn't the original question.

Clearly you don't want to do this (G&B Pickups):



Every soapbar bass pickup that uses this style of cover, i.e., nothing else to hold the pickup inside, is filled with epoxy.

Here's a set I did in customer supplied wooden covers:

[shawnl]

I have to admit that when I first looked into this, I misinterpreted what I was seeing and wrongly assumed that a coil should ever be encased by wax as a way of securing it to a cover.

I do understand the whole epoxy encasing method and know that you should use special potting epoxy and not something you buy from a hardware store. I haven't disregarded this method, although I do like the idea of having serviceable pickups as opposed to using something permanent like epoxy. Either way, I've worked out a system with small screws that fasten my wooden covers to the base of my coils through the sides. Since my design involves using a wooden plywood baseplate that glues to the lower bobbin of the coil and holds the magnet in place, this should work fine. For some reason, I didn't think of it before.

[David King]

I'll just add this to a thread that has been beaten into the ground. I've tossed plenty of bass humbuckers that were potted in epoxy into the trash when they developed an open coil or a short. You can interpret that any way you'd like but I for one, don't pot my coils into the covers. I don't even fasten them but let the spring around the screw or the foam rubber block hold everything in place.

David: if you want to handle all answers to all bass questions here exclusively, please be my guest. I'll take my time and knowledge and apply it elsewhere.

[jason lollar]

i would have to add if you did use typical potting wax as the only thing holding a pickup cover on- no solder no screws- as soon as the guitar gets set inside a car on a hot day that wax is going to be all over the place and the cover will be off. If you needed to glue a cover on (as mentioned before) hot melt glue will work and its easily released with a hot razor blade

[David Schwab]

David: if you want to handle all answers to all bass questions here exclusively, please be my guest. I'll take my time and knowledge and apply it elsewhere.

Not at all. You build more basses than I do! I enjoy your posts. But I think the OP is trying to do what is commonly done, but misunderstood how it was done. So I was explaining the usual method, assuming that's what he wants to do. New methods are always a good thing, but you don't want to reinvent the wheel if what you want is a wheel.

I sure wouldn't fill a pickup with wax for the reason Jason pointed out. It gets soft when it's hot. Some old pickups were made that way, and they haven't held up very well.

There is something to be said about being able to repair a pickup. But at the same time you are either making something that a person can repair that was not familiar with your pickups, or you are doing something that would leave a repair person scratching their head. Sometimes there are no user serviceable parts inside.

If epoxied pickups die, we can assume non epoxied pickups die. So let's take a commercial non epoxied pickup; how many times do we have to rewind a DiMarzio Model J or something? Would we know how to do it? Or would it have to go back to DiMarzio? What would they do with it? Send the customer a new one. Same thing I do if one of my pickups fails. They certainly wont repair it. So I think it depends on the pickup. If it's single coil Jazz pickups, then yes, leave those repairable. But then think of that multi coil Bartolini you took apart. That would be a pain. And it wouldn't have much solidity if not for the epoxy.

That's my opinion on it anyway. I don't expect that to be everyone's

[shawnl]

I think the OP is trying to do what is commonly done, but misunderstood how it was done. So I was explaining the usual method, assuming that's what he wants to do. New methods are always a good thing, but you don't want to reinvent the wheel if what you want is a wheel.

I did misunderstand and feel kind of silly, but I'm all the wiser now.

If epoxied pickups die, we can assume non epoxied pickups die. So let's take a commercial non epoxied pickup; how many times do we have to rewind a DiMarzio Model J or something? Would we know how to do it? Or would it have to go back to DiMarzio? What would they do with it? Send the customer a new one. Same thing I do if one of my pickups fails. They certainly wont repair it. So I think it depends on the pickup. If it's single coil Jazz pickups, then yes, leave those repairable. But then think of that multi coil Bartolini you took apart. That would be a pain. And it wouldn't have much solidity if not for the epoxy.

This is well put. However, my interest in serviceability has more to do with being able to save the fancy wooden covers should my home brew pickups turn out to be not so well designed. Once I'm certain I know how to make a quality pickup, I think epoxy seems like the simplest solution.