A look inside a Lane Poor MM5.

[David Schwab]

I think the issue here is that longer coils will see some significant stretching and shrinking due to ambient temp changes. If you encase the wires in something solid you have a higher probability of failure over time as the wire can no longer slide around a little as it reacts to temp changes.

Has that actually happened though? I have a Hi-A pickup I bought in 1976 and several very old EMGs and an even older Overlend EMG, and they all still work fine.

[David Schwab]

The traditional varnish for motor and transformer windings is Glyptal Home Page.

Wow, that's a truly dreadful website! They don't really tell you much of anything there.

This is not glyptal, but it's a varnish for another purpose: GC Electronics - 10-5002 - Allied Electronics

I've seen those varnishes before. A bit pricy, no?

[David King]

Possum,
I'm only going by the Bassics article referenced in the earlier thread, it makes no mention of bondable wire, only epoxy being sucked into the coil and then baked in a vacuum oven. That's not to say the article is factually correct but I'll bet that ordering bondable wire probably costs more. And since Lane was clearly conscious of his bottom line and since he'd already invested in the vacuum oven, I'm pretty sure he would want to use it whenever he could.

David,
I have seen many epoxy potted pickups go south, I think it has more to do with the winding tension than the epoxy used but Joe Guinn seems to imply above that a softer potting material might promote longevity in the coil.

I gathered up some more circumstantial evidence about the "bad batch" of LP pickups. At least one of them has the windings and magnets in phase so not hum-canceling at all.

[David Schwab]

I have seen many epoxy potted pickups go south, I think it has more to do with the winding tension than the epoxy used but Joe Guinn seems to imply above that a softer potting material might promote longevity in the coil.

It's not a bad idea.

One thing to notice here is the actual coils are encapsulated in regular epoxy. Then that cured assembly was encapsulated in the gummy stuff.

So that can't be the reason he did it that way. Maybe the other stuff was cheaper than the epoxy?

I gathered up some more circumstantial evidence about the "bad batch" of LP pickups. At least one of them has the windings and magnets in phase so not hum-canceling at all.

That's not good. I figured maybe some of them didn't have the shielding grounded.

[David King]

yeah they are nice and potted to the core, but not with wax, nor with the same black goop. I'm thinking its either bondable wire, or some form of laquer. I wonder if you could use an oven to bond the wire.. hmm

David,
Thanks, I did miss that detail.
I'm wondering now if the rubbery layer was to reduce microphonic handling noise?
Epoxy is about the cheapest stuff out there that doesn't take long and doesn't shrink as it hardens (or stink like polyester.)

Maybe it is bondable wire after all? Anyone ever price that stuff?

[automan]

I got a price list from MWS a while back, but can't seem to find that paper work since packing everything up and moving from Boston to Nashville. I'll see if I can dig it out tonight.

[Joe Gwinn]

Wow, that's a truly dreadful website! They don't really tell you much of anything there.

Yes. Old line industrial firm that was told by some consultant that they need a web presence.

I've seen those varnishes before. A bit pricey, no?

Yep. That's their business.

On the other hand, Glyptal will be happy to sell you a railcar of varnish.

Actually, I don't know their minimum order.

[Possum]

....

As a web developer I can tell you that most industrial companies are way behind the internet revolution, even now. Totally freaking amazes me they are still living in the 1980's. Then there are those that hire professionals to do nice websites and give them an email account and RFQ forms, then they never hire anyone to run the website and miss out on thousands and thousands of dollars worth of business because they don't have a clue. Thank God for companies like McMaster who got their shit together.

Now all that said are their liquids made specifically to pot coils and raise capacitance of the coil?

[Possum]

...

Oooops, are you talking about the Allied Electronics website? That ones is great. they do have Glyptal Varnish there, just saw it. Ordered their catalog, some cool stuff they have....

[David Schwab]

Oooops, are you talking about the Allied Electronics website? That ones is great. they do have Glyptal Varnish there, just saw it. Ordered their catalog, some cool stuff they have....

No, the Glyptal web site, if you can call it that.

Glyptal Home Page

[David Schwab]

On the other hand, Glyptal will be happy to sell you a railcar of varnish.

I would hope it would be cheaper than $10 for 2 oz!

I've been using spar vanish, which works fine. Before that I was using polyurethane.

[David King]

The problem with lacquer and other aromatic/ solvent based matrixes is that they need air to polymerize and air won't ever get into a coil so you have some strong reducers or solvents sitting around your insulation and trying their best to eat their way through it for 20 years. The solvents do gas off slowly over time but as they do the remaining material keeps shrinking down tighter and tighter around the coil.

Glyptal is a material that doesn't shrink much but it does need heat to polymerize. That's good. It's also designed to allow one to rewind a motor coil later on, you can probably burn it off or cut through it easily.

Epoxy is probably easier to deal with, it soaks in extremely well and cures completely from the inside out without any shrinkage. There are formulations that will give it flexibility or that might give it the same rates of thermal expansion as copper.

[belwar]

So that seems relatively easy, you need a material that uses a catalyst or hardener. It has to be thin at initial mix, and reach a good hardness within a few hours or after baking. Probably around 45-50A hardness.

A catalyzed RTV silicon would probably work very well. I use one to make quick molds that cures in 8 hours, and has a 45A hardness. mix up a batch, drop some coils in and vacuum out the air. Remove the coil, clean it off and 8 hours later you're done! No heat, no nothing.

[Sheldon Dingwall]

Has that actually happened though? I have a Hi-A pickup I bought in 1976 and several very old EMGs and an even older Overlend EMG, and they all still work fine.

Yup, hence my interest in this topic. The EMG humbuckers that Steinberger used had a problem with a coil cutting out too. They were really good about replacing them.

[tubby.twins]

I'd like to see one of the side winders... but this is what I expected of the humbuckers, and said so back in one of the original threads on LP pickups.

So, if the humbuckers weren't the "sidewinders" (or the "bilateral twin coils" as Lane called them), then which were? The wide aperture pickups? Has anyone opened up one of these yet?