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Post subject: Wiring P-Bass Pickups
Posted: Sat Jul 02, 2011 12:03 am
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I have had my p-bass since HS (over 12 years) and it had EMGs installed when I bought it. I have had some problems with some cracking/popping and decided to install some original p-bass pickups. I tried to follow the diagram but the volume/tone knobs are not working (almost always seem on/high) and there is a buzz. I thought this would be simple, and I am probably missing something small, but could anyone take a look at what I have so far and let me know if there is something obvious ive mixed up?

The pickups I have are on a copper plate, the black wire in from the top is attached to that.

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photo 3 by Seanbmc, on Flickr

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Post subject: Re: Wiring P-Bass Pickups
Posted: Sat Jul 02, 2011 2:17 am
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hello Hobbyist !!!

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Post subject: Re: Wiring P-Bass Pickups
Posted: Sat Jul 02, 2011 6:25 am
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Hi Sean & welcome to the forum.

About the only thing I can see wrong hardware wise is this appears to be a 3 contact jack and you only need a 2 contact jack in a passive set up. Still it should work fine if wired correctly.

The first wiring problem I think I may see is you may have the white wire and black wire reversed at the jack. Move the white one where the black one is and the black one where the white one is. I can not really tell which terminals are which in this photo for sure, but I would try that. White should be going to the tip connector and black to the shaft contact. The terminal for the tip ring should not be used.

The second wiring problem might not be a real problem at all as I can not tell for sure in this photo, but it appears that on the tone control pot the first lug from the left has a gob of solder on it so large that it might be touching the center lug. If this is the case it definitely would cause the tone pot to be non-functional. If solder from lug 1 is touching lug 2, desolder, resolder and that should fix it.

If those are the original pots, they might have been the issue in the first place and will still cause noise.

Pots in a passive P-Bass should be marked 250K. If you had active EMG's (which I suspect because of the 3 connector jack) and these are the same pots used in the active setup, then they might be the wrong value. They would work but for full range sound I'd use 250's.

Pickups usually work or they don't. Which is why I'd suspect that a pot or both pots were causing the noise. They can be sprayed with contact cleaner to clear that noise up and the spray will work way more often than not.

GOOD LUCK and let us know how it comes out.


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Post subject: Re: Wiring P-Bass Pickups
Posted: Sat Jul 02, 2011 8:38 am
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Thanks for the thorough reply. After going back over it this morning (wow that was some horrific soldering at 2am in the morning) I am thinking the POTS may be incorrect. They are labeled TO15A25K. So this looks to be a 25K pot that the EMGs use. I will try to put the EMG ones back together.

Do you know if Radio Shack would sell the POTS I need? I also saw some sets of wire kits online that I could order. After I posted last night I thought it probably would have been best to keep the EMG setup intact and get another kit so I could switch/compare between the two pickups easily.

Sean


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Post subject: Re: Wiring P-Bass Pickups
Posted: Sat Jul 02, 2011 11:06 am
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Radio shack probably dont have them,check any music store they are carried by even the smallest mom and pop music store and are fairly cheap no more than 6.00-8.00$$ a set,dont overheat them it will mess'em up.
This site has a section for wiring diagrams,check it out they make it easy for you.
G/luck

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Post subject: Re: Wiring P-Bass Pickups
Posted: Sat Jul 02, 2011 5:02 pm
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I went by our local music store and they had some 250k pots, they were not cheap though! I picked up some new wire and tried to get it working.

I get sound but the volume/tone knobs still do not do anything. I have a 104K capacitor in there, not sure if that is correct or would make a difference.

Here is a pic of the wiring with the new pots. I used red for white. The red is at the tip of the jack. Thanks again for taking a look. After spending most of the day, and too much money, im anxious to get this working :).

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Pbass by Seanbmc, on Flickr


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Post subject: Re: Wiring P-Bass Pickups
Posted: Sat Jul 02, 2011 10:50 pm
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Volume pot lug 3 (as counting left to right), which is the lug the cap lead is soldered to, should be grounded to the back of the volume pot. This is often done by bending the lug up and soldering the lug itself to the back of the pot, but you can also use a short jumper wire.

Guitar capacitor values are ordinarily stated in microfarads (uF), not Ohms. Your cap marked 104K uses the newer 3-digit and 1-letter method of labeling in which the cap value numbers are represented by the first two digits with a formula required to decrypt the value. A capacitor with the text 104K has a capacitance of 10 x 10 to the fourth power pF = 0.10 uF. In this newer method the K does not represent Ohms, but instead denotes the tolerance factor, which for "K" is + or - 10%. (J=5% and M=20%.) I do not like this new method myself as I have to get out my Picket slide rule. :wink:

This cap should work but might sound a tad dark for finger style players like me, but pick players might actually like it the best.

Typical passive bass caps will range from 0.022 uF to 0.10. On a P-Bass cap value that works best for me is almost always between 0.047 uF to 0.10 uF. Radio Shack does have some of those. I suggest starting with something around 0.05 uF as the higher the value the darker the tone and the lower the value brighter the tone.

Fender golden age instruments used paper in wax caps initially but soon switched to Ceramic Disc type capacitors. Fender switched to Poly in the 80's, but recently Fender returned to Ceramic Disc caps on their passive USA instruments. But Paper In Oil (PIO), Mylar and Poly caps will work too.

The order of capacitor types from least distortion to most distortion is PIO, Mylar, Poly, Ceramic Disc. Paper In Oil Vitamin-Q type caps are hard to find and expensive. I'd stick to Ceramic Disc types until you find the value you like because they are cheapest. Usually the caps at Radio Shack are clearly labeled in microfarads and do not use the cockamamie new 3 digit and 1 letter system.


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Post subject: Re: Wiring P-Bass Pickups
Posted: Sun Jul 03, 2011 7:55 am
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Woohoo, I see the tiny black ground line now on the diagram :). I think I am good to go now. A bit of noise when I touch the output jack, but nothing huge.

I had a horrific time trying to solder the grounds to the back of the pots. Its flat for the most part and the solder would not stick. Do you have any tips to get a solder to stick when it just refuses? Ive cleaned the surface, tried roughing it up some, and bought some Rosin-core. But im pretty sure the ground will pop off the tone know at some point soon.

After playing about 10 minutes the tone is much darker, next time I swing by radio shack I will pick up a .05. I didnt realize everything was this customizable, much fun!

Thanks for all the help. Ive now got two sets of pickups, the EMGs and the Original P-Bass that I can swap in and out easily.


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Post subject: Re: Wiring P-Bass Pickups
Posted: Sun Jul 03, 2011 10:31 am
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Location: Albemarle, NC
At Radio Shack the cap to start with will have a stated value of 0.047 uF. That is so close to 0.05 that it is basically the same due the wide tolerance factor on Ceramic Disc caps.

You should only use rosin core solder. I use rosin core silver solder. You have to be careful about overheating pots. The wafer disc inside the pot can be damaged. I drop a bead of solder onto the spot on back of the pot first. Then soften it by reheating and push the stiffened tinned wire tip into it as it cools. Then top it with another small bead. CTS pots seem to be pretty easy to solder. These do not appear to be CTS pots. They may have an oil film on them. Try some naptha (lighter fluid) or finger nail polish remover to remove any oils.

I would get some self adhesive copper sheeting and shield the back of the pickguard. That should clear up the hum issue. Actually I ordinarily shield the pickup cavity, the entire control cavity and the back of the pickguard on single coil basses. However on a P-Bass usually shielding the back of the pickguard is enough to make it dead quiet. You can get the self adhesive copper sheeting and any other parts you need (like real CTS pots) at Guitar Parts Resource Dot Com. The only things I can not get there that I use in a typical P-Bass set up are Vintage Sprague Vitamin-Q Paper In Oil and Mylar Sprague Orange Drop tone capacitors. I get those caps at Axe Grinderz Dot Com.

I like a really clean basic tone. You can "dirty up" a clean tone if you need to in several ways such as a pedal or Bass Driver type device or by overdriving the amp's input stage. However you can't "clean up" the basic instrument voicing once if leaves the instrument jack.


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