Since I got my pickup winder back up and running to make some TMI pickups I've been getting swamped with requests to repair pickups. I'm not really into it, and I have SO little time for extra work, but if it's something cool, or for a friend I'll usually say yes.
I've done a few WRHBs before and I recently did a huge "experiment" with lots of "aftermarket" WRHBs including different Maxon and Fujigen made versions and some modern ones where I rewound a seventies Maxon one with several different gauges of wire to see how close I could get to an original. That's another huge blog when I get time.
The anatomy of the original Fender WRHB is well documented so I won't really go into it too much (I'll give you plenty of pics) here. It was designed by the great Seth Lover for Fender in the early seventies and uses several unique design qualities giving them a very hard to replicate tone using traditional materials and methods.
The obvious difference from the outside is the size. They are physically bigger than standard (Gibson, also designed by Seth) humbuckers which picks up more string in the magnetic flux.
They also use a unique material for the poles, which was expensive at the time and is now unobtainium. Seth developed poles using CuNiFe (Copper/Nickel/Iron) material which was easier to machine and thread. These poles were magnetized making the threaded pole the magnet, as apposed to a regular humbucker which has a steel pole/screw near a bar magnet (s) attached to the bottom of the assembly.
Anyone who has tried slug pole P-90's (my favourite and ones I make for my guitars) knows the difference between the pole being the magnet, and the pole directing the magnetic flux. Personally I think the magnetic pole pickup is more articulate.
So, with wider bobbins, physically bigger pickup and rare metal magnetic poles the WRHB was, and is a beast all it's own. There are some very convincing "clones" out there using modern materials and techniques, and as I've said before (and will again when I get that other blog written) I really like the middle period (full size) Maxon (late seventies Greco) and early Maxon and Fujigen (early Fender Japan) versions a lot. To my ears, they do an almost perfect job of replicating the original, even with completely different design and wire gauge. But then, Maxon were and are one of the great electronics companies in musical history.
Anyway, back to this '74 Tele WRHB. It came in in an old Fender and one coil was dead in this pickup. The other coil still measured a good 5.4K so I carefully pulled the pickup apart to see if I could find a physical fault with the pickup.
No luck. It all looked OK so I removed the bad coil and started unwinding. As I've said in previous pickup repair blogs, I start unwinding the coil to see if there's a break/fault near the end of the coil that could be repaired keeping the original coil intact. No such luck here so I cut the wire off and cleaned up the bobbin.
The original Fender WRHB used AWG42 poly wire so I rewound it with the same wire. Notes from previous ones I've fixed (and that experiment) showed I needed "about" 6500 turns to get the desirable resistance. I thought I'd go for 6600 and If that was too many I can always unwind some to suit. I did this because the other good coil was slightly high (it depends on many factors) as these are "normally" around 10K or just over.
With 6600 turns on the bobbin I took it off the winder and measured it. 5.6K was good so I unwound some and reassembled the pickup. I managed to reuse the original yellow tape that I'd taken off the coil and everything went back exactly as it came apart.
I tested the output and phase with my signal generator and scope and everything looked great so the cover was put back on and soldered in place.
This can go back to the shop to be put back in it's beautiful vintage Tele. I didn't clean it up at all as the guitar is absolutely hammered, in a good way, and it would have really stuck out if I cleaned it all up and polished it. It looks so good like this and still suits the rest of the guitar. Ready to fight again.