Potting

[Paulkstadden]

Actually, it's a Biflux in the neck. Diggins sent me a really good closeup of it (he's fabulously nice about that, he's sent me a lot of pics of his guitars in progress!) I'd always read that it was a Magnum, even reading it in a mag with an interview with Iommi. Then he sent me that pic, and there it was, "Biflux by John Birch" written on the cover. Presumably, they were all hand engraved, maybe even by Birch himself, but I don't know.

Yeah, the P-90 size makes it difficult to copy! Getting bobbins, covers, and baseplates is impossible without custom making them. Diggins just got the tooling in to make the P-90 sized copies and he is making a new copy of the old Jaydee guitar for Iommi! As soon as he can make a Magnum, I'm definitely ordering one! I will be taking as many readings as I can.

I'd love to know about your newly potted pickups. Any info I can get before making one, I'll take! Again, I've made stuff without researching first and ended up with crap. No more!

[David Schwab]

Actually, it's a Biflux in the neck. Diggins sent me a really good closeup of it (he's fabulously nice about that, he's sent me a lot of pics of his guitars in progress!) I'd always read that it was a Magnum, even reading it in a mag with an interview with Iommi. Then he sent me that pic, and there it was, "Biflux by John Birch" written on the cover. Presumably, they were all hand engraved, maybe even by Birch himself, but I don't know.

Ah, ok. On Iommi's page it says:

The pickups are of different types, the bridge is a Jaydee special and the neck is a John Birch style Magnum X in a John Birch casing, though made by John Diggins.

I'm sure John knows what he made! John makes very nice basses.

I'd love to know about your newly potted pickups. Any info I can get before making one, I'll take! Again, I've made stuff without researching first and ended up with crap. No more!

They are bass pickups... soapbar humbuckers. I'm finished testing them, and now it's time to pot them. I'll be doing that tomorrow morning. You need a closed cover. Pour some epoxy in and place the guts on the pickup in it.

Here's one in the "test" bass. (it's covered in blue painters tape to protect the cover from scratches.)

[Paulkstadden]

The closed cover, that would explain why Gibson's Iommi pickup has the closed cover. Still, how would one do it with a cover that's got holes drilled in? Those old Magnums had the row of balance screws but were still epoxy potted, how'd Birch do it?

By the way, love the bass, looks like some nicely flamed maple on that top.

[Paulkstadden]

Actually, here's a nice shot from Jaydee's site. The writing can be seen on the neck pickup.

[Sweetfinger]

Check your old guitar NOW! for celluloid deterioration

I don't see how celluloid would cause corrosion on a plated brass cover and wires... celluloid is not much different from nitrocellulose lacquer. You'll notice only the metal parts have been affected.

Different enough in some cases. Look Here
http://aic.stanford.edu/jaic/article...-02-003_3.html
and here
http://www.balisongcollector.com/celluloid.html
and some more
http://en.wikipedia.org/wiki/Celluloid
The effects of celluloid decomposition on metals are well known, and when you look at some of the compounds formed during decomposition, like nitric acid, it isn't hard to see how a brass cover or wiring can be eaten away. You should consider yourself lucky that the government has not seen fit to regulate old pickguards the same way it has regulated the storage of old nitrate film stock. You'd have to store all chunks of old funky binding, and pickguard in steel drums UNDER WATER!

[David Schwab]

The closed cover, that would explain why Gibson's Iommi pickup has the closed cover. Still, how would one do it with a cover that's got holes drilled in? Those old Magnums had the row of balance screws but were still epoxy potted, how'd Birch do it?

It can be done. Pick up a copy of Animal Magnetism for Musicians, written by the guy that makes Q-Tuner pickups. He shows a bunch of bass pickup designs that are all cast in resin, and some have adjustable poles. You have to wax them so they don't stick!

Epoxy potting is messy work. I wouldn't want to bother with adjustable poles!

By the way, love the bass, looks like some nicely flamed maple on that top.

Thanks! I love that bass. I stopped using it for a while because I made the string spacing at the nut as wide as a P-bass, which was a bit much for a 5 string! So I removed the hardware and put them on my zebrawood bass.

Now I like the neck on the maple bass, so I'm making new pickups for it. It has a great tone. The two basses sound quite different.

[David Schwab]

You should consider yourself lucky that the government has not seen fit to regulate old pickguards the same way it has regulated the storage of old nitrate film stock. You'd have to store all chunks of old funky binding, and pickguard in steel drums UNDER WATER!

StewMac stopped carrying celluloid binding because it's flammable.

To this day most movie theaters still have the thick walls on the projection room, with the tiny hole for the projector (and a big steel door) because of the old explosion risk!

I see your point about the celluloid. But still the coil forms on those old pickups didn't look deteriorated. They certainly looked better than my old Mustang pickguard!

[Paulkstadden]

The book looks excellent. Amazon has it for cheap.
I love his wood pickup surrounds. And those pickups he makes look rather funky, too. I see the coils of wire, but what the heck are those things in the holes going through the pickup? Some sort of polepieces?

[David Schwab]

I see the coils of wire, but what the heck are those things in the holes going through the pickup? Some sort of polepieces?

Pole pieces. Hex (Allen) screws actually.

[Clint Searcy]

I don't see how celluloid would cause corrosion on a plated brass cover and wires... celluloid is not much different from nitrocellulose lacquer. You'll notice only the metal parts have been affected.

Here's the bobbins. I don't know what they are made from, but they look intact. Of course I'm just going by the photos. I haven't seen the pickup in person. I'll ask Clint what he thinks the bobbins were made of.

Hi folks,

I'm glad to see that my work has sparked some debate. I welcome any alternate points of view about the cause of the extensive corrosion found in both of these pickups. There have been some good suggestions mentioned here and I considered and rejected most of those as I worked to solve this mystery.
To best understand this case it's important to know that the coils inside these pickups were held in place with nothing but bees wax. All parts were totally submerged in wax. This allows us to rule out things such as beer or other liquids being spilled into the pickup. There’s no way it could have gotten that far into the wax. Plus, the wood in to bottom of the cavities is as clean as the day they were made. No stains or other evidence of spilling exists.
Celluloid deterioration is an interesting suggestion but the guitars have no celluloid parts and are 100% original. Also there is no damage to any of the other metal parts of the guitars so that can be excluded as well.
Salt air? Again, the pots, hook up wire and output jacks and other metal parts are all clean and corrosion free. Yet the parts inside the pickup covers that should have been protected from salt air by the wax were all heavily corroded.

It's also important to understand that this potting wax was not bought at the local Arts and Crafts store. This wax likely came straight out of the hive. In post war Finland there was no easy place to find parts and supplies. This information combined with several articles on the corrosive nature of natural bee’s wax all point me in this direction. There are two competing theories on why this happens. One states that the wax itself can have a high enough acid content to cause corrosion. The other suggests that the wax acts as fuel for Microbiologically Influenced Corrosion to occur.

Here are some interesting articles on the matter.

http://findarticles.com/p/articles/m...03/ai_n7473723

http://palimpsest.stanford.edu/byfor...2000/1313.html

https://metropolitanmuseum.org/Works...2003/mixed.asp

Now, I'm not suggestion that everyone run out and replace all their wax. Clearly it seems that not all bees wax exhibits this trait. But working on these pickups has convinced me that the possibility is very real. I think it’s important to pass that information along.

[Joe Gwinn]

Hi folks,

I'm glad to see that my work has sparked some debate. I welcome any alternate points of view about the cause of the extensive corrosion found in both of these pickups. There have been some good suggestions mentioned here and I considered and rejected most of those as I worked to solve this mystery.
...

So, it really is the beeswax.

Now, I'm not suggestion that everyone run out and replace all their wax. Clearly it seems that not all bees wax exhibits this trait. But working on these pickups has convinced me that the possibility is very real. I think it’s important to pass that information along.

Nor is it common to use pure beeswax in pickups, and mixtures will vary.

[Clint Searcy]

Nor is it common to use pure beeswax in pickups, and mixtures will vary.

True, I would assume most are using the 80/20 mix you and I use. But those who restore old and odd pickups might find this information useful.

[David King]

Could someone have used acid core solder at some point inside these pickups, perhaps to solder the cases together?
I apologize in advance if this was already ruled out, I can't focus long enough to read 3 pages of posts.

[Clint Searcy]

Could someone have used acid core solder at some point inside these pickups, perhaps to solder the cases together?
I apologize in advance if this was already ruled out, I can't focus long enough to read 3 pages of posts.

I'm not sure that it was mentioned here David but I did think about that possibility. The problem is that these pickups were made using coils from surplus WWII military radio handsets. In other words, the person who soldered the covers together and soldered the volume pot and out put jack was not the same person who soldered the coil connections and as you can see in this picture the connections into the coil failed from corrosion.

[Spence]

[QUOTE=Joe Gwinn;16642]So, it really is the beeswax.


QUOTE]


How do you know it's pur beeswax? Had it tested? Are we to assume that the bees producing this wax were drinking acid rain? The mystery deepens....

BTW, what's the coating on the coil wire and the lead-off wires? I suspect a chemical interaction here.