Tiesco Gold Foil Pickup Construction

Morgan · Post by **Morgan** » 16 Jan 2012, 06:51

Hey guys,

I have this Tiesco pickup I'm trying to patch up for a buddy that has intermittent operation (the pickup, not the buddy). It's not the typical gold foil you see around; quite a bit different. I pulled it apart to look for a bad solder joint or something, and it's got really strange construction methods going on in there. The ground lead is soldered to the casing, the coil is wrapped in paper, and the hot lead just floats; it's not actually connected to anything, and it sure looks like it's meant to be that way. The hot lead wire is stripped about 1/4", tinned, but has not been crimped and looks likes it's never been attached to anything. The stripped portion of the outer jacket has been inserted over the hot lead to keep it from shorting to anything. There is no evidence of a physical connection with the coil at all.

Anyone come across these before and have any troubleshooting tips? The metal band that runs perpendicular to the coil seems to have something to do with the intermittent operation, but nothing I can measure with a DMM. Twisting it or applying pressure sometimes brings it to life. The ground connection is solid. I suspect a broken winding, but would like other opinions.

Thanks!

bmxguitarsbmx · Post by **bmxguitarsbmx** » 30 Jan 2012, 21:14

In order to provide a signal, some sort of circuit has to be made. Somehow electrons need to flow.

I would assume the transducer is electromagnetic, but possibly not. Does this pickup attract ferrous material, such as a screw?

I will assume for the moment it does. I will also assume that those metal "retainer clip like" parts are connected to one end of the coil, and the other end of the coil comes out of the brown paper end near the hot lead. Typically magnet wire for guitar pickups is similar in size to a human hair. Quite hard to see!

My advice is to remove the coil that is inside the brown paper, being very careful not to snap any connections to the clips. I would assume the clips are soldered in to make the ground connection. Try to imagine how they assembled it. It will be delicate, but hopefully you can take a single wrap of the magnet wire off and re-attach it to your "hot" wire.

Sometimes magnet wire does not want to solder and you may need to remove the insulation with some 600 grit sandpaper.

These guys may be able to offer better help:)

http://music-electronics-forum.com/f11/

blackbunny · Post by **blackbunny** » 31 Jan 2012, 03:05

bmxguitars has pretty much nailed it. I repaired one of these pickups successfully and gave up on another one several years ago....I hope you like a challenge.

bmxguitarsbmx wrote: I will also assume that those metal "retainer clip like" parts are connected to one end of the coil, and the other end of the coil comes out of the brown paper end near the hot lead. Typically magnet wire for guitar pickups is similar in size to a human hair. Quite hard to see!

IIRC, the "clips" are just there to locate the paper-wrapped coil on the baseplate. I had to de-solder the cable ground and remove the output cable from the case, then de-solder and remove the tab that goes across the case, then bend the tabs up carefully.

I used a hot iron with a large flat tip to de-solder the cable ground, and had lots of heatsinks on hand to cool the baseplate down quickly. The paper wrapping will provide some heat insulation for the coil for a short time only.

Remove the wrapped coil extremely carefully - the wire will be very brittle due to ageing. Inside the wrapping is a small bar magnet which may be glued to the base plate, or may have separated from it.

You will then need to look at the paper wrapping with a magnifying glass to find out where the coil end wires originally came out, and carefully separate the paper wraps with an X-acto type hobby knife.

Peel the paper back, find the coil ends, check for continuity, carefully bare the wires (I gently scraped the insulation off with the fine blade) and tin, ready for attachment to the output lead.
Then re-seal the paper wrap with a couple of drops of Elmer's glue or a rubbery contact glue, align the coil between the tabs and glue the magnet back to the baseplate, solder one coil wire to the baseplate and then solder the cable ground, apply heatsinks, solder the other coil wire to the hot lead, check for the coil continuity, re-bend the tabs, re-install the tab that goes across the coil and you're done.

Good luck!

.

bmxguitarsbmx · Post by **bmxguitarsbmx** » 27 Mar 2012, 02:33

Well... I have been looking at these Teisco pickups a bit differently lately. I have rewound a couple and have been asked to "wax pot" one of these things. I own a pretty sweet Teisco and upon purchasing it, I attempted to show off by guessing its resonant frequency. I guessed 3.6KHz, based on 3.1kHz being the highest resonant Strat coil I have ever measured. I tested the pickup the way I always do, by generating a fluxtuating magnetic field;) Resonant frequency was measured as less than 1kHz for all three pickups! Unfortunately, no one laughed at me because electro-humor doesn't exist.

Maybe I am the only one that finds this interesting, but the reason I guessed so wrong is obvious. If you look at a lot of the Teisco guitars the switches say, "Mic". I didn't even think that it might, actually, be a "mic"! An electrodynamic microphone and the familiar electromagnetic transducers we are used to as guitarists are very similar:

The "microphone" consists of a moving coil that moves inside a stationary magnetic field.

The "common guitar pickup" consists of a stationary coil inside a moving magnetic field.

Admittedly, current is induced in many guitar pickups by the moving coils and moving magnetic fields. The teisco "mic's" certainly are. Acoustic measurements of the Teisco "mic's" in my guitar all had resonant peaks quite closely grouped around 3.85kHz. This is quite high! And they are pretty killer little deals to play:).

Anyway. They are peculiar and lovely. Please don't "wax pot" them! Hopefully this information is useful to someone.

Cheers,
Ethan

blackbunny · Post by **blackbunny** » 27 Mar 2012, 06:07

Wow! I thought the metal cover looked a bit different from the ones I opened up in the 80's - they're not the same thing at all.
Can you explain a bit more about the moving coil? Does it have a diaphragm, or is the thin foil on the top of the pickup the vibrating element/diaphragm?
Do the pickups have even string balance between the bass and treble strings?
Is there a fixed magnet, a moving magnet, or does it rely solely on electromagnetic current generated from the surrounding coil, with no magnet at all?

bmxguitarsbmx · Post by **bmxguitarsbmx** » 28 Mar 2012, 16:01

Hi Blackbunny

The magnet is stationary. The "diaphram" appears to be the loosely wound coils and the soft plastic former. I think the foil does have something to do with acoustical coupling. The ones I have had access to are the gold foils. The foil is on a soft, foam-like backer. When the pickup is assembled, the foam presses against and hold's the coil under, at least a small amount of, tension. No elaborate suspension at all. The rolloff is quite steep after resonance (~4.8kHz)

I haven't personally seen an example of the one the OP posted. It definitely looks different than the ones I have inspected. I have some photos on my phone, and will add to this post as I figure this posting stuff out;)

I tried to post to this blog... But, I don't see me;) so... If you do accidently pot them, send them to me. I'll do my best:)
http://www.cloudyproject.com/potting-teisco-pickups/

Cheers,
Ethan

blackbunny · Post by **blackbunny** » 31 Mar 2012, 13:53

The ones shown on the CloudyProject website are convential single coil p'ups similar to P90 single coils with bar magnet and slug polepieces, and are a lot like the ones I repaired way back when.
I can see why wax potting wouldn't work on the "microphone-style" gold foil pickups, as they seem to rely on the physical movement of the coil and former.
I'd guess that the gold foil p'ups would have a low output level and the tonality would be completely different from the "conventional" single coils.

matt239 · Post by **matt239** » 20 Jun 2013, 07:51

I'm pretty sure they're not intentionally constructed as microphones, they're just magnetic pickups, and are microphonic by accident.
I don't doubt however, that this contributes to their unique sound, so they might be quite different if they were potted.. - or, not... ?
There are even reproductions of the gold foils now!