Secrets of the early 60s mini humbuckers..

Dougie

Senior Member
Joined
Dec 11, 2008
Messages
2,013
Reaction score
1,115
I recently had the fun of taking apart a DOA mini humbucker from about 1964. This would have been used on an Epiphone guitar as Gibson made those pickups for Epiphone in those days.

The early minis are known for their super cool tone which is nice and rounded and full, nothing like the thin sounding squealy later minis that went on the LP Deluxe guitars of the 70s. This was mostly due to different materials, different magnets and different winding wire, but leave it to say that the old minis sounded so good because they were wound with the same plain enamel wire as PAFs, they used the same magnets as the short magnet PAF, and Gibson wasn't afraid to fill the bobbins completely full.

Many of these early mini humbuckers have DCR measurements well over 7.5k, minis with readings as high as 7.97k are not uncommon. There, is the question. How did they get these readings on such small bobbins?

Modern 42ga AWG magnet wire reads about 1.6Ω per foot, 43ga reads about 2.1Ω per foot, but the wire that came off the dead coils of the 1964 mini humbucker reads 1.866Ω per foot.

That would explain how the same number of turns of vintage 42ga wire would give a much higher reading as opposed to modern wire!

Now, did Gibson buy wire back then that was that far out of spec because they could get it cheaper? And did some of this wire get used in other pickups like the PAF and therefore explain how some of those come out reading 9.3k and others much lower even though they both have 5,000 turns on each coil? Or were they just winding pickups with the wire as supplied and not paying much attention to it's quality control?

I mean it wasn't then and isn't now rocket science, but it sure makes you wonder.

I cannot get modern 42ga wire to duplicate the vintage mini humbucker readings. About the most you can get on a mini bobbin is 4700 turns, which gives a reading of 3.55k, considerably lower than readings you would find in a vintage mini that read 7.8k overall.. Sure I can use 43ga and get the dcr up there but it's not the same, the capacitance and inductance is not the same as the off-spec wire used in the early minis..
 

Frogfur

Senior Member
Joined
Jan 18, 2013
Messages
20,014
Reaction score
35,945
Interesting.
Thanks for that information.
 

LtKojak

Senior Member
Joined
Aug 26, 2009
Messages
4,157
Reaction score
3,020
Modern 42ga AWG magnet wire reads about 1.6Ω per foot, 43ga reads about 2.1Ω per foot, but the wire that came off the dead coils of the 1964 mini humbucker reads 1.866Ω per foot.

That's right.

Bill Megela, Electric City Pickups has recently mentioned 'bout the wide differences in ohm-per-foot readings of the wire he'd found, repairing PAFs from the '50s.

I can only guess that the cause was a machine/s with "too much" tension in the traverse, so the wire "stretched" while being wound in the coils.

Elektrisola and BAE wire can custom spec a AWG #42.x wire for ya, measuring anywhere from 1.75 to 1.95 ohms-per-foot, but you'll need to buy a whole batch, costing several thousands of dollars.

HTH,
 

freefrog

Senior Member
Joined
May 21, 2011
Messages
1,600
Reaction score
990
I cannot get modern 42ga wire to duplicate the vintage mini humbucker readings. About the most you can get on a mini bobbin is 4700 turns, which gives a reading of 3.55k, considerably lower than readings you would find in a vintage mini that read 7.8k overall.. Sure I can use 43ga and get the dcr up there but it's not the same, the capacitance and inductance is not the same as the off-spec wire used in the early minis..

Thx to share!

OT note: in the same way, I wonder how a vintage Strat PU that I've measured can give 2,2H @ 400hz with a DCR of 5.4k (and alnico rods of the smallest diameter). Especially when I compare it to a contemporary Custom 69 reading 2H only for 5.85k...:hmm: Materials from yesteryears were definitively different.

To come back to your mini's: Impurities in the copper wire?

Also Dougie: if you have ever measured the inductance of vintage mini's, could you post it too? :)
 

Bluefox

Senior Member
Joined
Mar 2, 2013
Messages
709
Reaction score
591
About the differences in DCR on vintage pickups, Walt Fuller said in a interview that it was due to different actual thickness of the wire received from batch to batch. Seth Lover also talked about variances in actual diameter of the wire in a interview with Duncan, if I recall right. That's why, to me, a modern replica with a DCR of 9k doesn't sound like a vintage PAF reading 9k because that value is due to different reasons.
One has more turns of regular wire, the old one most of the times has a wire half way between 42 and 43 and sometimes even closer to 43.
According to Fuller the accepted tolerance was 10% with occasional exceptions.
 

Dougie

Senior Member
Joined
Dec 11, 2008
Messages
2,013
Reaction score
1,115
I don't have a meter that reads inductance but I want to get one. I have a pair of early PAT # minis, NOS, they read 7.72k and 7.16k @80° I'd like to know what henries they read.
 

bill m

Senior Member
Joined
Aug 14, 2010
Messages
1,860
Reaction score
2,398
I don't have a meter that reads inductance but I want to get one. I have a pair of early PAT # minis, NOS, they read 7.72k and 7.16k @80° I'd like to know what henries they read.

You can send them up to me and I'll take all the measurements for you( Inductance, ACR, Q, Capacitance, ETC). I take all measurements at 68 degrees so there is a reference point.
 

zoork_1

Senior Member
Joined
Apr 22, 2009
Messages
1,218
Reaction score
556
Sorry for derailing the thread, but I'm having a microphonic squeal problem with a mini and thought this was the right place to ask for advice... :eek:

I have fixed the loose pole piece screws and experimented with masking tape placed on the mounting ring/cover. That helped a lot, but it's still too microfonic.

I don't want to disassemble it or give it a wax bath, so I need to figure out other ways to deal with the problem.
I'm beginning to think that the springs have a part in this... :hmm:

Your advices are most welcomed... :acoustic:
 

freefrog

Senior Member
Joined
May 21, 2011
Messages
1,600
Reaction score
990
Sorry for derailing the thread, but I'm having a microphonic squeal problem with a mini and thought this was the right place to ask for advice... :eek:

I have fixed the loose pole piece screws and experimented with masking tape placed on the mounting ring/cover. That helped a lot, but it's still too microfonic.

I don't want to disassemble it or give it a wax bath, so I need to figure out other ways to deal with the problem.
I'm beginning to think that the springs have a part in this... :hmm:

Your advices are most welcomed... :acoustic:

I have far less experience than you with old pickups but let's try to help...

-AFAIK, squeal might come from slugs touching the baseplate (if not from the rough cast magnet vibrating on it). In various occasions, I've put a piece of soft material between these elements : either it was adhesive tape stuck on the baseplate, either it was a kind of semi rigid cellophane sheet simply slipped between the slug coil (and/or magnet) and the baseplate (the two bottom screws had been pulled off then I've rescrewed them in the slug bobbin through the cellophane).
This solution doesn't appear to alter the tone, although I've recently noticed a resonant peak shifted up with one pair of PAF replicas treated like that. I still don't know if it's due to a lesser stray capacitance, to reduced eddy currents or to a modification of the magnetic field by the slight gap due to the plastic sheet between magnet and baseplate.:hmm:
...Unless it's an artifact due to my testing gear. :D

-Screws: I've already encountered squeal which stopped when I touched the height setting screws... I think it's due to the springs. I've passed the whole screw/spring assembly through a drilled bar of foam on each side...
It works but as I've refastened the 4 coil screws AND added tape here and there in the same time, I don't know if that "foam tubing" alone kills the squeal.

Hope to be useful...

PS for Dougie: thx for the answer and sorry to derail your thread too...
 

zoork_1

Senior Member
Joined
Apr 22, 2009
Messages
1,218
Reaction score
556
I have far less experience than you with old pickups but let's try to help...

-Screws: I've already encountered squeal which stopped when I touched the height setting screws... I think it's due to the springs. I've passed the whole screw/spring assembly through a drilled bar of foam on each side...
It works but as I've refastened the 4 coil screws AND added tape here and there in the same time, I don't know if that "foam tubing" alone kills the squeal.

Hope to be useful...

Thanks alot, I'll give the screws a shot.
I should have mentioned that the squel increase dramatically when I put my hand close to the pu... :confused:
 

Dougie

Senior Member
Joined
Dec 11, 2008
Messages
2,013
Reaction score
1,115
It's probably the cover squealing. When I put covers on I clamp the pickup into the cover so it is tight against it, this seems to help a lot. Some people put tape or even a bead of silicone on top of the bobbins and this helps to dampen the cover, but you have to open it up to do that and on a mini, especially an old one where the coil tape can be like tar and stick to the inside of the cover, you can kill the pickup very easily trying to get it open. Nevermind if it's a PAF mini and desoldering it or wax potting it can destroy much of it's collector value.
 

zoork_1

Senior Member
Joined
Apr 22, 2009
Messages
1,218
Reaction score
556
It's probably the cover squealing. [...]...[...]. Nevermind if it's a PAF mini and desoldering it or wax potting it can destroy much of it's collector value.

Thanks, I think I will replace it with a fullzized one and let the case rest for a while... :hmm:
 

Dougie

Senior Member
Joined
Dec 11, 2008
Messages
2,013
Reaction score
1,115
Some gut pics of the restoration :D

Dead pickup, taken apart:


Dead coil, showing plain enamel magnet wire, same wire they used on the legendary PAF pickups.


Coils rewound and taped up with new leads and a new braided lead soldered on the baseplate. Note the magnet, this is the same magnet used in the '61 to '63 short magnet PAF pickups.. Think that might be a hint as to why these early mini humbuckers sounded so good?


Rewound coils seriesed together and connected to the braided lead, ready for the cover to be installed.


Finished pickup connected to a Fluke multimeter, nice hot reading, much hotter than the '70s mini humbuckers that came later in the Les Paul Deluxe guitars.


Pickup mounted in "Waldo" my $15 piece of junk test guitar that I got at a Waldo Florida flea market.


The pickup sounds great. It has a nice round clear bottom end, great mids and a biting edge to the highs. It has the mids these are known for, semi compressed sounding and muscular, it's a tightness that full size HBs don't have. It sounds like a Custom Bucker in that it is really even across the frequency spectrum, if I had to compare it I would say that it is a cross between AC/DC and Atlanta Rhythm Section.

It is also a true hybrid, with scatterwound asymmetrical coils, 42ga/43ga respectively, and like the full size Duncan SH-16 59/Custom hybrid it also gets a very slight bit of that early EVH "Brown Sound" although not nearly as much as the SH-16. Pretty cool sounding pickup for a mini. It would definitely wake up any LP Deluxe!

Note: I may list this in the members classifieds since I don't have a guitar that uses mini humbuckers. I also have a period correct PAT # sticker base plate for a LP Deluxe that I could swap out to fit it into a LP Deluxe pickup ring.
 

zoork_1

Senior Member
Joined
Apr 22, 2009
Messages
1,218
Reaction score
556
Here's a mini PAF VS full size PAF... :yesway:

Bridge position, same guitar, amp and settings:

[ame=http://www.youtube.com/watch?v=vhvqRBGw0SU]Full size PAF VS mini PAF - YouTube[/ame]
 

Dougie

Senior Member
Joined
Dec 11, 2008
Messages
2,013
Reaction score
1,115
Very nice! Great blues chops and great tone!
 

GitFiddle

Senior Member
Joined
Jun 1, 2010
Messages
11,162
Reaction score
14,161
I don't have anything technical to contribute, but I do have a set of what I understand to be 60s Gibson minis on this old Silvertone, made by Harmony or Kay (can't remember which at the moment).

Apparently they made some kind of trade with Gibson at the time for body blanks or something, but Gibson provided them with a large bucket of minis. That is supposed to be what came stock in this guitar.

They sound amazing, but I have never really been able to gig with this guitar since, its a true hollow body arch top and feeds back too much at stage volumes.

If there is any measurements or readings I can take (without having to disassemble the pickups), I would be happy to help out.

gitfiddle-albums-65-silvertone-1446-picture46913-silvertone100-1092-400-x-600.jpg
 

Dougie

Senior Member
Joined
Dec 11, 2008
Messages
2,013
Reaction score
1,115
AFAIK, Harmony made that model for Silvertone, those are some neat minis in there too. Never read one of those but they sound great. Prized by collectors as well, they fetch a nice sum on fleabay.

If you want to read them simply crank all the knobs wide open and stick a male jack in the output and read off the terminals of the jack.
 

GitFiddle

Senior Member
Joined
Jun 1, 2010
Messages
11,162
Reaction score
14,161
AFAIK, Harmony made that model for Silvertone, those are some neat minis in there too. Never read one of those but they sound great. Prized by collectors as well, they fetch a nice sum on fleabay.

If you want to read them simply crank all the knobs wide open and stick a male jack in the output and read off the terminals of the jack.



I came up with 6.97K on the bridge and 7.12K on the neck.
 

Latest Threads



Top