Any valuable info on Lane Poor MM pups?

[LtKojak]

That's an EMG-SA. It gave its life to science!

Wow, in that picture it looks like an awful lot of wire in those bobbins... what wire is it?

[David Schwab]

Wow, in that picture it looks like an awful lot of wire in those bobbins... what wire is it?

Yes it is. I haven't checked it, but I think it's 43 AWG. Talk about winding until the bobbins are full!

The humbuckers are the same way.

[Joe Gwinn]

Well bad news today everyone... The doc called me from the Radiology department and said the medical X-ray was not powerful enough to penetrate the pickup.. He said I'm going to have to find an industrial X-ray company.. dang. I'll have the pickups back in my hand today and will start googling now.

What voltage and current did he use? For things containing metal, one needs high voltage (to penetrate) and low current (to not destroy the X-ray tube), and a long exposure.

But I'm guessing that the doctor knew to set up as if to visualize big bones, not flesh. The old machines would allow one to do almost anything, but the new ones may be overly automated and thus limited.

Is this epoxy potted? Some makers will fill the epoxy with sand to hinder reverse engineering.


How do I know of the old machines? In the 1970s, I had a girlfriend who was an X-Ray Technician at Johns Hopkins Hospital in Baltimore. I took a jewelery making course, and made for her an X-Ray Pendant. On the outside, it looked like a solid hunk of brass about 0.1" thick. When X-Rayed, the inner heart shone through.

[ModulusMK]

How do I know of the old machines? In the 1970s, I had a girlfriend who was an X-Ray Technician at Johns Hopkins Hospital in Baltimore. I took a jewelery making course, and made for her an X-Ray Pendant. On the outside, it looked like a solid hunk of brass about 0.1" thick. When X-Rayed, the inner heart shone through.

Nice work with the gift, good idea

[David Schwab]

Is this epoxy potted? Some makers will fill the epoxy with sand to hinder reverse engineering.

Sand? For that glassy tone, huh? I've seen filler for epoxy, but not heard of sand.

How do I know of the old machines? In the 1970s, I had a girlfriend who was an X-Ray Technician at Johns Hopkins Hospital in Baltimore. I took a jewelery making course, and made for her an X-Ray Pendant. On the outside, it looked like a solid hunk of brass about 0.1" thick. When X-Rayed, the inner heart shone through.

Clever!

[Joe Gwinn]

Sand? For that glassy tone, huh? I've seen filler for epoxy, but not heard of sand.

Sand is common, as it's cheap and available. So, maybe the result is that cheap glassy tone?

I recall answering a question (on the old AMPGE forum?) about how to protect a circuit from reverse engineering. My answer was to design the board to allow washing in hot water, wash the assembled and soldered board in a domestic dishwasher, put in potting shell with the leads hanging out, sift fine clean sand in, then infiltrate with thin catalyzed epoxy resin. This would raise the effort to disassemble and reverse engineer to the point of impracticality for all but the largest of companies.

[belwar]

Well I decided to have some fun at lunch today..

I hacked apart half of my LP P pickup. Several surprises..

1) I thought the pickup was wired in parallel because of the low DCR.. Combined is was about 2 and change.. So I figured 4k coils in parallel.. Nope! The coils were in

series and each one about 1-1.5 kohms..
2) The whole coil was wrapped in what looked like either gold or brass foil... Its definetely not copper.. Thats probably why the X-ray couldnt see inside..
3) The actual coil part is encased in clear epoxy, not black. yeah!


Now on to the construction of the pickup
1) The bobbin is constructed from single side copper clad circuit board, approx 0.05" Thick
2) Bobbin dimensions are .75" x 1.75". Total thickness is 0.356". Inside thickness (coil former height is 0.252").
3) Wire is heavily leaning towards the bottom of the bobbin.. i.e. not a flat layer, but like the traverse was too far over and wire piles up on one edge.
4) Coil apears to be wrapped in a white/cream masking tape.
5) Coil was not in the pickup parallel to the top. It was either put in the epoxy sloppy. Probably 4-6 degrees off along the narrow edge. It is even along the long edge.
6) Wire seems to be 42 awg .. possibly heavy build formvar. Calipers read either 0.0030 or 0.0035 on a good sample..
7) On the thick side of the coil the wire protrudes 0.1150"
8) There is one magnet, no pole pieces..
9) Magnet size is 0.25" x 0.25" x 1.26
10) Core is wrapped in the same masking tape.
11) The coil I hacked was the coil WITHOUT the LP logo, and it was south down.
12) South Side of Magnet max gauss was 1084 using an GM-200A
13) Average South Side strength was 950.
14) Wire is dark brown / red.. pretty much the color of the attached picture..

[David Schwab]

series and each one about 1-1.5 kohms..

Just like my old low Z pickups.

8) There is one magnet, no pole pieces..

Ceramic?

[David King]

It's a ceramic magnet? I think it's our key. If we can find out whether it's C5 or C8 and who made it I think we have a good chance of getting the sound back again.

Are you sure it's 42 heavy and not 41 single?

Can you take a guess at how many turns are on there?
Is there's a steel core and the magnet is underneath the bobbin or is the magnet inside the bobbin?

I'm afraid a P pickup won't tell us much about any of his other pickups.

[belwar]

Well this one was just a start.. Im going to do the jazz one next.. The jazz is a narrow apeture.

I was able to get one 12" piece of wire off without streching it.. I lightly sanded the ends like I do with PE and my cruddy DMM first read 2.2 ohms, but then changed to 3.9 ohms... seems high.. the wire DOES look thicker than 42.. It could be 40-41, but I have to mind a more accurate way to measure. 2.2 would be in line with slightly streched 42 awg as that is 1650 ohms/1000 feet. The added thickness Im seeing could be a result of the epoxy coating..

I just used calipers again and it came out 0.0025".

I just cant see 41 being used though.. It's not as easy to buy 40-41..

How can I tell if its ceramic? Does anyone have the chemical differences between C5 and C8?

[David Schwab]

This is like the old Alembic formula. They used 40 AWG and about 1500 turns directly on a ceramic magnet. So it's like an air core coil. No steel core, as that increases the inductance, which would warm up the tone quite a bit, but also decrease some high end.

This is what I suspected earlier.. a low wind/low inductance pickup.

The Q-Tuner is similar, as it does not have steel cores, they are air cores, but it does have steel poles.

But from the earlier article posted, it sounds like some of the Poors have steel poles.

[tubby.twins]

Belwar, I'd be interested to know more about what you find in the way of magnets in the Jazz pickup that you're (probably) about to cut open.

By sheer luck, I think I just discovered something about the magnets in my Lane Poor pickups. Using a piece of magnetic paper, I saw that the wide aperture magnet looks much more "shallow" than the narrow aperture magnet. I've attached some image links, so hopefully this will show you what I mean.

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Above is the magnetic paper placed over the short end of the wide aperture pickup (model SB4250). Notice that the green line on the magnetic paper appears curved and shallow, which implies to me that the magnet is very near the top of the pickup shell, and does not extend deeply below it.

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Above is the same magnetic paper placed over the short end of the narrow aperture pickup (model JB4250). Notice that the green lines don't connect, but go all the way from the top of the pickup to the bottom.

Below is another photo of a "loose" (never installed) JB4250 pickup. I had to enhance the brightness and contrast in this photo here as well.



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More close-up images (contrast-enhanced) of the magnetic paper on the top surface of the JB4250 shell. If this pickup is indeed using 9 pole pieces, I can't see any sign of that with the magnetic paper. There don't appear to be any obvious patterns that I would associate with pole pieces.

I hope this is helpful. I actually have to give the credit to my kids, who were hovering around me in my bass room (during one of the rare moments when I can sneak in a few minutes of practice) offering to "help daddy play the bass" (which usually involves them strumming the strings at full volume) and one of them ended up picking up the magnetic paper and holding it over the pickups. It was at that moment that I noticed the apparently shallow magnet in the wide aperture pickup.

[belwar]

Tubs (Like your new nickname? :> ),

That was definetly very helpful and cool! I dont see any pole piece use at all.. I think these pickups are alot more simple than I was expecting.. Did I understand that you have an MM4? would you mind doing that same test with that as well?

Also where did you get than paper? I would love to get some of that.

bel

[tubby.twins]

Tubs (Like your new nickname? :> ),

That was definetly very helpful and cool! I dont see any pole piece use at all.. I think these pickups are alot more simple than I was expecting.. Did I understand that you have an MM4? would you mind doing that same test with that as well?

Also where did you get than paper? I would love to get some of that.

bel

Thanks, Bels. I don't have a MM4 - here are the remaining Lane Poor pickups that I *do* have:

2 x JB4250
1 x SB4250
1 x JL-N
1 x M4.0 W
1 x M4.0 HB

I found the magnetic paper on eBay several years ago. I think I have a spare sheet - let me dig around a bit and I'll let you know.

[tubby.twins]

I couldn't find my spare sheet(s) of magnetic viewing paper, but I found two places online that sell something very similar.

Magnetic Viewing Paper 4" x 4" - $6.50 each for a 4" by 4" sheet

Magna View Film - Science Gifts - Edmund Scientific - $10.95 for two 4" by 4" sheets

There are other vendors out there, but most seem to sell the smaller strips (2cm by 5cm) which aren't as useful for pickups.