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 Post subject: RWRP Bridge Pickup Mod Tutorial
 Post Posted: Sat Apr 16, 2011 6:10 pm 
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Joined: Mon Mar 05, 2007 12:33 am
Posts: 3403
Location: Denver
A few years ago I remember forum member BlueAngel posted that he had done an RWRP modification to his c. 2006 4003's bridge pickup. This mod essentially puts a 4003 on the same plane as a Jazz Bass as far as hum canceling, i.e. when both pickups are on, at the same volume and in the same phase there is significant 60 Hz hum reduction. Under other conditions (unequal volumes, 0.0047 cap in-line) the hum canceling won't happen.

I was intrigued by this mod. I had noticed the occasional hum issue with my 2007 4003, although it was not a frequent problem. It mostly happened at home and not at gigs. On the other hand, why wouldn't you want the option to cancel hum, when needed? For rock music, where I typically use both pickups full-on, it seemed like an ideal situation. After reading BlueAngel's description I tackled it and came out successful. But I was nervous doing the job; that I got it right the first time was a bit of skill and probably a bit of luck. Either way I was spared some frustration. The result was not even a slight change in tone, just an OCD-soothing absence of hum in the pickup blend mode. Years later this pickup configuration is still going strong for me; I recently gigged the 4003 and it was a show-stopper. Lots of compliments.

Last week I decided to do this again for a second bass. It's the second time I've done this mod and I've made a photo tutorial for others who want to do the same.

1. Measuring the pickups--two single coils with fairly similar resistance are ideal for canceling hum.
Image
Image

2. Observe what the bottom of the pickup looks like for reassembling it. An eyelet connects the ceramic magnet to ground, as well as the lead shield and a second eyelet that grounds the pickup surround. Closer inspection of the primary eyelet shows the grounded end of the coil soldered to it and the hot end of the coil in a heatshrink-covered joint with the lead wire. These joints will have to be spliced.
Image
Image

3. I like to "label" the stock ground wire of the pickup coil with a piece of Scotch tape. This will be spliced back as the hot wire after reassembly. Cut the hot and ground connections on the coil side leaving a 0.5'' section behind so you can strip them later and have a decent-sized lead.
Image

4. Remove the bobbin from the magnet and label the side that faces the bobbin "RP" (for reverse polarity). Rotate it 180 degrees horizontally, and put the cut leads back through the same holes in the magnet.
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5. Remember to line up the bobbin and the magnet so that the screws will connect.
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6. Reassemble the magnet, bobbin, and phenolic baseplate. Put heat shrink on the coil leads before soldering them in their new configuration (the one with the Scotch tape on it goes to the pickup lead wire).
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7. This is how my pickup looks after reassembly. I measured it with the multimeter and it measures about 100 ohms higher than before--probably heat from the soldering iron creeping into the coil. In a few hours it will go back down to the room temperature value.
Image

There you have it! Just some free info for those seeking it... hope it helps you, whoever you are.

cassius


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 Post subject: Re: RWRP Bridge Pickup Mod Tutorial
 Post Posted: Sun Apr 17, 2011 11:33 am 
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Joined: Sun Oct 08, 2006 6:07 am
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Cassius, thanks for taking the time to photograph the process.


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 Post subject: Re: RWRP Bridge Pickup Mod Tutorial
 Post Posted: Sun Apr 17, 2011 12:22 pm 
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Joined: Tue Aug 09, 2005 1:00 pm
Posts: 2588
Location: The Rickenroom
Nice pictorial step by step, Joshua! Good job! :)

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 Post subject: Re: RWRP Bridge Pickup Mod Tutorial
 Post Posted: Mon Apr 18, 2011 5:22 am 
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Joined: Fri Jul 07, 2006 5:00 am
Posts: 527
Location: Winchester, VA USA
Great job Joshua, now you just need a video version for YouTube and all will be right with the world! :D


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 Post subject: Re: RWRP Bridge Pickup Mod Tutorial
 Post Posted: Mon Apr 18, 2011 1:34 pm 
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Joined: Tue Mar 22, 2011 7:36 pm
Posts: 26
Location: Deux-Montagnes, Canada
Nice tutorial! Just have a question about which way you rotated the magnet(I dig in the other treat and I can't really find my answer), did you rotated the magnet 180 degree on it horizontal longer axis(side to side), but if you do so, from what I know about magnet that will be useless as the pole didn't move, OR, you rotated it on the vertical(top to bottom) axis like if you put the magnet flat on a table(the way it is installed stock on the bass), hold it in the middle and spin it half a turn? That last option make more sense to me, but if you can confirm that will be nice. Thanks
Dom

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 Post subject: Re: RWRP Bridge Pickup Mod Tutorial
 Post Posted: Mon Apr 18, 2011 3:45 pm 
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Joined: Mon Mar 05, 2007 12:33 am
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Location: Denver
The magnet is removed, then flipped over on the long axis... if it's a rectangle, you grab one of the long ends and flip it over. This changes the polarity but lets you keep the same holes for the leads. If you flip it the other way, the polarity changes but the holes don't line up right.

EDIT: Hopefully this pic explains it better than my words:

Image


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 Post subject: Re: RWRP Bridge Pickup Mod Tutorial
 Post Posted: Mon Apr 18, 2011 4:29 pm 
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Joined: Wed Jan 16, 2008 3:58 am
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Location: En Zed
Yes, that picture works. What you meant to say is that the magnet is rotated (flipped) around the short axis...


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 Post subject: Re: RWRP Bridge Pickup Mod Tutorial
 Post Posted: Mon Apr 18, 2011 5:19 pm 
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Joined: Tue Mar 22, 2011 7:36 pm
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Location: Deux-Montagnes, Canada
That make sense, I didn't figured out that third axis and the hole alignment!!
thanks you

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 Post subject: Re: RWRP Bridge Pickup Mod Tutorial
 Post Posted: Mon Apr 18, 2011 8:44 pm 
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Location: Denver
cjj wrote:
Yes, that picture works. What you meant to say is that the magnet is rotated (flipped) around the short axis...


Oops, I guess I'm confused as to how to describe the axes. I need to go back to college physics! Maybe even high school geometry. :oops:


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 Post subject: Re: RWRP Bridge Pickup Mod Tutorial
 Post Posted: Mon Apr 18, 2011 10:04 pm 
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Joined: Sat Nov 22, 2008 6:58 am
Posts: 83
Location: Michigan
Sometimes the magnet is glued or stuck on the bobbin. If that's the case, go slow when separating them because the rubberized magnet can crack.


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