Potting pickups; tape before or after?

[David Schwab]

Yeah, but I have no plans for public sales. Gotta buy a bass to get them!

I'm looking forward to that also!

Im slowly saving for the bobbin injection mold - It takes me about 1.5 hours to make enough bobbins for 1 bass. That is FAR too long at my $8/h wage. The bobbin mold will cost about $1800, and the cover mold is about $3500. That's not chump change by any means.

Believe me, I know! I've looked into injection molding in the past. For covers I can't buy, I'm doing them with a 3D printer and making molds. That's very time consuming also.

I've actually been thinking about putting a wal style jazz p/u together.. 4 coils at around 10k.

Not pretty to look at, but here's the guts from a 5 string Jazz pickup I made around 1992. This is the bottom of the pickup. One magnet is missing. The coils came from the old Thomas Edison factory in West Orange before they razed it. There is a threaded pole piece that sticks through the perf board, and came up through the cover. I had them wired in series, but they were still low Z, so I ran them through a preamp. It sounded really cool in the bridge position on my Ibanez SR-885 with flatwound strings.

[Mark Hammer]

I recently bought some clear plastic bobbins at a dry goods / sewing-supplies store. I haven't used then yet but they seem sturdy enough. And they were cheap.

[David Schwab]

Thanks for your comments guys! My bobbins are made of 2mm acrylic and acrylic tube. I just hope ca glue holds up the potting temperature.

It does. All my bobbins are put together with CA. Some of them have steel blades for the core. I leave them in the wax for 10 minutes. Haven't had any come apart yet.

I used 22mm hole drill with center drill to get enough acrylic washers and then used my drill press a lathe to turn them smaller. It certainly is not a too fast way of making them, but for single/couple of pickups it's acceptable. They are 17,5mm diameter as I'm making this pickup for 54mm string spacing. Then I glued these acrylic washers to 19mm pieces of acrylic tube.

Wow, on a drill press huh?

There was JUST enough room to get enough wire for 2.45Kohms.

That's what the real thing reads. Was that about 10,000 turns? Damn, making these pickups takes time...

I'm going to use 5mmx19mm Alnico or Neodymium rods as magnets. Now I have to pot the coils and make the base out of circuit board. I'm going to make part of the connections on the board.
Marko

I have some neo rods to try, but I haven't done it yet. The real pickup has quite a bit of steel in it.

Here's the circuit board. This was a pickup for a passive Pro Series bass. The MK basses have the coils wired differently. It's a very clever idea to use a PCB. Bartolini has been doing that for years, and Duncan and DiMarzio do that now as well. That's going to be my next step for all my pickups.

[David Schwab]

I'm just curious as to why these would need bobbins at all? Seems like they could just be wrapped around magnet (over some tape) and between two temporary, non-stick washers that would get peeled off after potting and reused.

Because the real pickup has adjustable poles.

[Marko Ursin]

Wow, on a drill press huh?

Yes, I stacked 16 washers and got a lump of acrylic that was 32mm high and 22mm thick at the beginning. Turning them smalles was actually pretty fast. Drilling them out of acrylic sheet one at the time and forcing the partly melted acrylis out of the hole saw was not.

That's what the real thing reads. Was that about 10,000 turns? Damn, making these pickups takes time...

If my bicycle speedometer-based calculator is set correct it was 10,650 turns. I wound four in one evening, then SWMBO asked me to stop and spend some time with her and our son. If these pickups were made for living I guess there had to be some sort of automatic multicoil winder, not an old press drill

About wiring these coils; If I understood correct the passive Pro has four coils in series and the stack of fours in series again. Correct? Was the newer, "active" way the two coils for the same string in series and these four stacks in series again? I have wound four coils in clockwise and four coils anti-clocwise. Then I have to put the magnets cw wound four N up and acw wound four S up to get hum cancelling, right?
Marko

[David Schwab]

About wiring these coils; If I understood correct the passive Pro has four coils in series and the stack of fours in series again. Correct?

Yes.

Was the newer, "active" way the two coils for the same string in series and these four stacks in series again?

The active has the two coils for each string in series, and then each of those comes out of its own wire, and they are connected in parallel at the preamp.

I have wound four coils in clockwise and four coils anti-clocwise. Then I have to put the magnets cw wound four N up and acw wound four S up to get hum cancelling, right?
Marko

Yes. You don't have to wind them in reverse, just wire them up in reverse. The original has all the coils wound in the same direction. When you wind in reverse, wire them up all in phase.

[Marko Ursin]

Yes. You don't have to wind them in reverse, just wire them up in reverse. The original has all the coils wound in the same direction. When you wind in reverse, wire them up all in phase.

Meaning start of one coil to the end of another coil or how?

Is this correct?

S=start of coil E= end of coil

hot E----S-E-S-E-------S-E-S-E----S ground

Marko

[Chris Turner]

I recently bought some clear plastic bobbins at a dry goods / sewing-supplies store. I haven't used then yet but they seem sturdy enough. And they were cheap.

I did the same. Just plain old plastic sewing bobbins. They're 3/4" diameter, and 3/8" tall, with a 1/4" hole in the center. You can just turn them down a bit if you need a tighter string spacing.

They're the common Class 15 type, like on this page: Bobbin Dimensions

And, while I haven't tried it, you could probably use something like this to wind them on the cheap: Electric Bobbin Winder

[David Schwab]

Meaning start of one coil to the end of another coil or how?

Is this correct?

S=start of coil E= end of coil

hot E----S-E-S-E-------S-E-S-E----S ground

Marko

Then the coils are wound the same you wire them start-finish --> finish-start. Then you wind them opposite you wire them start-finish --> start-finish.