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Post subject: 1975 Precision pickup repairs
Posted: Sun Sep 01, 2013 1:57 pm
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I've got a modified '75 Precision for repair from a friend.

The bass has been upgraded with Badass II bridge and J pickup on bridge apparently long ago.
The problem is that when neck (P) pickup is activated, the tone gets twice weaker. Bridge pu alone works fine.
I've disassembled the instrument and took measurements.
The problem is in one half of the P pickup, which reads 315K, while the other, healthy half reads 5.71K.

No noise or hum.

I've checked the wire and apparently it looks undamaged, but it's probably something inside.
The pickup is original Fender's '75 P with tight coil of some black wire.

I assume if the wire is somehow damaged the only possible repair should be rewiring the coil with new wire. I'm not winding pickups and I'm not sure I can find a proper wire for that.

My question:
Am I right and the wire is damaged - or is this some other problem? It is not completely broken, it produces sound, so maybe I've missed something?

In any case, what's the suggested repair?

As the bass is already modified it's probably not about keeping it stock, but a '75 P pickup is a valuable thing and I'm not going to simply swap it with some new pu.


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Post subject: Re: 1975 Precision pickup repairs
Posted: Sun Sep 01, 2013 4:18 pm
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A '75 factory P p'up valuable????
:lol: :lol: :lol: :lol: :lol: :lol:

My '76 Fender factory P p'up died suddenly and most unceremoniously in 1985. I threw it in the trash where it belonged. You should too. Utter garbage. Sounded like $@!& from the day it was born. Plant it in the landfill and be sure to use plenty of weed killer.

Die CBS Die!

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Post subject: Re: 1975 Precision pickup repairs
Posted: Sun Sep 01, 2013 9:01 pm
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From the way you describe the sound it sounds like the 2 pickups are out of phase(?) and maybe switching the hot and ground to get the right hookup where they both are the same volume? Not sure- and I may not have described what I mean properly. Also The readings for the pickups don't sound right. Maybe you don't have your multi meter set right. Brother Dave !!!!!!!


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Post subject: Re: 1975 Precision pickup repairs
Posted: Mon Sep 02, 2013 12:20 am
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2 stroker -
The pickup is the most regular Precision, two coils out of phase.
I've unsoldered them, so each coil is measured independently.

I wonder if there's some sort of a pro forum where I can post the question, something with guitar repairs rather than just bass players....


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Post subject: Re: 1975 Precision pickup repairs
Posted: Mon Sep 02, 2013 2:28 am
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That reading of 315k possibly means there is a break in the winding somewhere. The reading should be very close to the 5.71k reading you are seeing on the other half of the pair. If those are accurate readings, and I have no doubt they are accurate, it needs rewinding back to spec. Usually when there is a break in the winding it will be completely dead, so the fact it is working at all is good.

Time was that every guitar repair place did pickup rewinding. Now not as many. Check around for local shops that do rewinding. If you can not find anyone locally then you'll be mailing it off to one of the pickup specialty shops. Rewinding with most of them is about as costly as one of their new pickups. For economy rewinding by mail, try Brandon Wound Pickups. They don't list bass pickups specifically on the website but Brandon Wound Pickups does rewind bass pickups for way less than anyone else I've found online. They charge $25 per bobbin so $50 for both plus shipping. I'd get both bobbins rewound to the same spec as the original. Since one has broken the other could go anytime...or it might last another 50 years, you just never know.

Or you could do what was suggested and just replace it with a new pickup. That would be way faster and really cost very little more. If you do go the replacement route there are several good pickups out there that aren't insanely pricey. The problem though will be finding one that balances well with the Jazz pickup and does not overpower the Jazz pickup completely. I suspect that overpowering the Jazz pickup was also a problem with the original pickup when it was fully functional because the CBS era pickups got more overwound as time went by. The Seymour Duncan SPB-1 Vintage Pickup is a possible option here and goes for about $65. That is about the same as rewinding the original pickups with related postage expense. It is wound more like pre-CBS specs (less overwound) than the one that the instrument has now. It is a good pickup. So is the Fender Original Precision Bass pickup. The Fender one costs a little more though usually. For sure avoid anything overwound at all or described as "HOT" else you'll never hear the Jazz pickup at all.

Also this instrument probably needs 500K pots in it if they didn't do that already when they put the Jazz pickup in it. If it has 250k pots I'd change them to 500k ones probably.

One consideration normally would be keeping the instrument original, but that went out the window with the Jazz pickup modification and I'd have no problem putting new pickups in it instead of rewinding the originals. I'd save the old pickups though in case you decide to rewind them later.


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Post subject: Re: 1975 Precision pickup repairs
Posted: Mon Sep 02, 2013 6:10 am
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Noticed you say the winding looks fine on the surface. I'm not surprised as it almost always does appear totally normal when a pickup dies. As you stated they die inside. It happens in the winding due multiple shorts or even just one break in the winding wire. I suspect a good bump or two would kill the one reading 315k so that it reads zero.

The enameled wire used to wind vintage bass pickups is almost hair thin. Fender used larger gauge Formvar wire which has a synthetic resin coating on some electric Spanish guitar pickups but the bass pickups always got the thin enameled wire for tonal reasons. Over time dust, dirt and moisture will get into the windings. The larger gauge Formvar wire isn't immune to wearing either.

The worst thing to get into the pickup winding is metal filings from fretwork or screw head filings because the magnetic poles in the pickup just pull any jagged metal filings deeper and deeper into the winding holding it there and when coupled with vibrations generated by playing the instrument you can guess the outcome.

You can usually blow a cloud of dust off a pickup with compressed air, DustOff or similar products. But you can't blow away metal filings due the magnetic attraction of the pole pieces holding onto the metal.

The thin enamel serves as an insulator. Eventually due aging of the enamel it can begin to break down all by itself resulting in fluctuating impedance readings, but the presence of dust, dirt etc speeds up the process due friction caused by normal playing vibrations in the bass. Wherever the enamel completely breaks down on overlapping and touching turns, you get a short circuit of sorts which bypasses the turn. Magnetic poles also will weaken over time as the pickup ages.

As any foreign matter works into the windings it has a growing potential to completely break a turn of wire eventually, but metal filings do it much much faster and are the worst possible thing to get anywhere near a pickup. When a turn of wire breaks connection the pickup is usually dead silent and not just weaker.

Whenever doing any sort of fretwork, you should tape up the pickups completely, do the fretwork, then blow off the instrument with compressed air when the metal work is done. Next you should tape OVER the existing tape with another layer of tape. Lastly remove all the tape as if it was one piece so the two layers do not separate thus trapping any stray metal particles that didn't blow away between the tape layers. I am serious about this, metal filings are a pickup killer. Frequently people get some fretwork done (or do it themselves) and 2 weeks or a month later the pickup goes dead.


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Post subject: Re: 1975 Precision pickup repairs
Posted: Wed Sep 04, 2013 8:42 am
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engels wrote:
2 stroker -
The pickup is the most regular Precision, two coils out of phase.
I've unsoldered them, so each coil is measured independently.

I wonder if there's some sort of a pro forum where I can post the question, something with guitar repairs rather than just bass players....


Oh boy- what's that supposed to mean? There are electronic engineers that post here and Bro Dave ... well.... okay. :shock:


Sorry to sound defensive but that kind of reminds me of the way a lot of players and people place "unimportance" on bass and bassist. I've experienced it many times. If they only knew.......


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Post subject: Re: 1975 Precision pickup repairs
Posted: Wed Sep 04, 2013 7:19 pm
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stroker vance wrote:
engels wrote:
2 stroker -
The pickup is the most regular Precision, two coils out of phase.
I've unsoldered them, so each coil is measured independently.

I wonder if there's some sort of a pro forum where I can post the question, something with guitar repairs rather than just bass players....


Oh boy- what's that supposed to mean? There are electronic engineers that post here and Bro Dave ... well.... okay. :shock:



Sorry to sound defensive but that kind of reminds me of the way a lot of players and people place "unimportance" on bass and bassist. I've experienced it many times. If they only knew.......


He is just not accustomed to being Linninized. While Linnin is probably correct, his approach didn't exactly make him a candidate for the Diplomatic Corps.

Would like Retroverbial to check his resistance readings and see what he thinks is going on. Pretty sure this is a rewind or replace scenario.


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Post subject: Re: 1975 Precision pickup repairs
Posted: Wed Sep 04, 2013 9:27 pm
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brotherdave wrote:
stroker vance wrote:
engels wrote:
2 stroker -
The pickup is the most regular Precision, two coils out of phase.
I've unsoldered them, so each coil is measured independently.

I wonder if there's some sort of a pro forum where I can post the question, something with guitar repairs rather than just bass players....


Oh boy- what's that supposed to mean? There are electronic engineers that post here and Bro Dave ... well.... okay. :shock:



Sorry to sound defensive but that kind of reminds me of the way a lot of players and people place "unimportance" on bass and bassist. I've experienced it many times. If they only knew.......


He is just not accustomed to being Linninized. While Linnin is probably correct, his approach didn't exactly make him a candidate for the Diplomatic Corps.

Would like Retroverbial to check his resistance readings and see what he thinks is going on. Pretty sure this is a rewind or replace scenario.





The first thing I did to my 74 P bass in 79 when I bought it was replace the stock pickup with a Dimarzio Model P. ($50) The stock pickup sat in my cabinet ( and other such places) for 30 years until I reinstalled it in 2009. It sounds okay. I think the Dimarzio sounds better. It's in another bass now.


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Post subject: Re: 1975 Precision pickup repairs
Posted: Thu Sep 05, 2013 5:08 am
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linnin wrote:
A '75 factory P p'up valuable????
:lol: :lol: :lol: :lol: :lol: :lol:

My '76 Fender factory P p'up died suddenly and most unceremoniously in 1985. I threw it in the trash where it belonged. You should too. Utter garbage. Sounded like $@!& from the day it was born. Plant it in the landfill and be sure to use plenty of weed killer.

Die CBS Die!




" unceremoniously" is a very big word. I hope that doesn't offend you.

My 76 P bass pickup wasn't even in my 76 P bass when I bought it. So what does that tell you? It tells me someone may have disposed of it at the landfill. I wonder if they would let me in there with a metal detector? :)


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Post subject: Re: 1975 Precision pickup repairs
Posted: Thu Sep 05, 2013 7:22 am
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I would replace the Precision pickup with a Fender original '62 precision bass pickup to get the bass operational.

Since the bass is already routed for a Jazz pickup, it has limited collector value but probably an enhanced player value because it is more versatile with the jazz pickup installation.

As much as some of us old timers hate the CBS era, those basses are reaching amazing values and their components are also respectable in the prices they command on ebay and craigslist. I would rec. that you hang on to any original parts of your '75 Precision, including dead pickups, bridges, pick guards, tuners and bridges and pickup covers. All of these parts are getting more valuable every day and even though your current bass may not be collectible, You may come across a '70s era bass that just needs a Bad*SS bridge replaced to make it 100% original.

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Post subject: Re: 1975 Precision pickup repairs
Posted: Thu Sep 05, 2013 12:11 pm
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As Brotherdave mentioned, that low resistance means that the coil is open. The other thing that was mentioned is that since it has been modified with the jazz pickup routing it is less valuable from the collectors standpoint. I would recommend (the cost effective option) is to get a p/j set. There are a lot of options: Seymour Duncan, Fender, Bartolini, EMG, etc...

The perfect sound is totally subjective!! I suggest you go to the links of these manufacturers and read the specs. I prefer Seymour Duncan's Quarter pounds or the Hot pickup series! There's also the Antiquity series for the beat up look! Good Luck!!

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Post subject: Re: 1975 Precision pickup repairs
Posted: Thu Sep 05, 2013 12:31 pm
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Yes as I said earlier, the Fender Original Precision pickup is a good option and keep the old pickup. The Duncan SPB-1 is a very similar pickup that is just a few bucks less. I don't know what Jazz pickup is being matched to, but usually they are all dominated by the P-Bass pickup, so you have to try to keep to vintage type specs.

The Dimarzio Model P is a good pickup, but it is hotter than a vintage pickup and might not balance as well in volume with the Jazz pickup. I'd put it in the HOT category making it less suitable for use in a P/J in which the J is stock wound.

Two other vintage sounding pickups I've thought of that would work in a P/J with a stock wound Jazz pickup are the WILDE P-46 at $60 plus shipping which sounds vintage while looking non-vintage correct and the Bill Lawrence PB1 which runs about $55 and both looks and sounds vintage.

((Both the WILDE pickups and the Bill Lawrence brand pickups were designed by Bill Lawrence. WILDE pickups are his most recent and possibly last bass pickup designs for use in a Fender style bass. The "Bill Lawrence" brand offers pickups he designed in the 1970's to early 1980's which are conventional wax potted 2 lead designs with 4 poles per P-Bass pickup and 8 poles per Jazz pickup. In 1984 he sold out his interest in Bill Lawrence pickups to his partner and that company is still making his older designs. This is like Leo Fender selling out to CBS who kept making Mr. Fender's old designs while he moved on to new designs at Musicman and G&L. Lawrence's most recent WILDE pickups are sealed in a Lucite type resin, meaning they should last nearly forever, so long as the poles don't get demagnetized. The resin sealing also means they can never be rewound, but they should never need rewinding since nothing can ever get into the winding to break the winding and they are even immune to typical aging. The resin also makes them a tad heavier and the covers non-removable. The WILDE P/J set has extra poles on each pickup, 10 per P-Bass set on the P-46 or 9 per Jazz pickup on the J-45, so they will work with either a 4 or 5 string bass but they still will fit in most standard P/J routing on a 4-string. The Wilde P/J set also has one extra wire per pickup, which might mean slightly expanding any drilled out wiring channels. This extra wire, blue in color, makes it possible to wire the WILDE P/J set in a VOLUME/BLEND/TONE setup using conventional un-ganged guitar pots, which is what I did with mine. It can also be setup in the conventional VOLUME/VOLUME/TONE arrangement. So far as I know it is the only P/J set with this option in the world and further proves Bill Lawrence's genius. This is an excellent vintage sounding P/J set with cutting edge design features costing $124, but it doesn't look vintage correct due to the extra poles. It will outlive any player.))

Either of those or the Fender Original Precision or the Duncan SPB1 are good options to use with a stock Jazz pickup. I might go ahead in this case and get the WILDE P/J set as they are custom balanced in output to each other. That in fact would be the best move but also the most costly. I use this $124 P/J set and like it, but the poles are different from true vintage pickups because there are MORE of them. Still a good option in any P/J though, just not a strictly vintage correct looking option due the extra poles.

If you do replace original 250k pots with 500k pots, save the old wiring harness as-is, which means you will also replace the jack and tone cap. Just pull everything and attach it to a piece of cardboard and put it in a zip lock bag along with the malfunctioning pickup and put in new pickup, pots, cap and jack and completely rewire everything from scratch. I personally prefer 500k pots in any passive P/J and a 0.05uf tone cap.

The WILDE P/J set when wired in the Volume/Blend/Tone arrangement uses a unique Bill Lawrence circuit that will also require a .02uF to 0.10 uF treble bleed cap in addition to the traditional 0.05 tone control cap and the special circuit diagram is included. I actually used a 0.18uF cap which read 0.192uF and it sounds pretty good. If you want to cut more highs use a higher value. Bill Lawrence just says to keep it from 0.02uF to 0.10 uF and to experiment to find the one you like best.


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Post subject: Re: 1975 Precision pickup repairs
Posted: Sat Sep 07, 2013 3:32 am
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Engels apparently never came back. Congratulations to us on our excellent customer service skills here at first tier support.


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Post subject: Re: 1975 Precision pickup repairs
Posted: Sat Sep 07, 2013 10:47 am
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Thanks for the advices, I do come back by the way.
Special tanx to brotherdave. I think you've covered the subject.
I tend to buy a new fender P reissue pu and sell the damaged stock pu on ebay.
Now it depends on my friend to decide.


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