I wired this Wilko Johnson Telecaster up a while ago, and at the time I noticed a problem with the middle pickup position. The neck and bridge pickups were fine on their own, but the blended, middle position was weak. Low in volume and “tinny” – with a “nasal” sort of sound. I immediately identified the problem as likely to be down to either the polarisation of one of the pickups, or the winding of the pickups, (or maybe both). Turns out the bridge and neck pickups I’ve chosen aren’t immediately compatible – and the signals are out of phase. They cancel each other out.
Sometimes, Telecaster pickups are paired so that when they’re combined in the middle position – they have a “hum-cancelling” effect. The set may be wound so that the pole orientations or coil directions of the different pickups are still compatible when combined – working together to cancel out any interference in the signal. However – a problem sometimes arises when pickups from different manufacturers, or from different sets, are mixed. It’s difficult to tell what polarity pickups have, just by looking at them, and without a special tester. Even the advice that a particular pickup is “reverse wound”, or “reverse polarity” means nothing unless you know what it’s the opposite of. However – if you do identify, (or suspect), a partially cancelled signal in the blended position – there’s usually a potentially easy fix. This involves the switching over of the hot and ground leads, from one of the pickups, at the connection to the switch. This effectively reverses the signal from one pickup, and can put the signals from the two pickups properly into phase. There’s just one complication, in this case.
And that’s because both pickups have extraneous metal components, (a heavy baseplate on the bridge pickup, and the lipstick cover on the neck pickup). These are both directly hardwired to the pickup ground wires on each pickup body, via short jumper wires. One of these connections has to be severed, and a new ground connection created for one of the pickups. This will switch the original “hot” and “ground” signal routes – effectively reversing the direction the induced current travels in. Crucially – severing the ground hardwire jumper, means that the extra metal plate isn’t brought into the “hot” side of the circuit when the wires are reversed.
I’m not sure why I’ve left this so long to fix. I know, sometimes, that when I finish a build – the last thing I want to do is to take it all apart again, just to fix some annoying little bug. I know also, at the time, I didn’t particulary want to scrap a new set of strings either. I think, other builds definitely got in the way too. (Plus the fact that this Tele gets most of it’s use with the selector set in the bridge position). Anyway – since I’ve got the Tele out of it’s case for a while – I’ll see if I can quickly resolve my little problem now…
I can theoretically reverse the signal path on either pickup, but if I try and resolve the issues at the neck – then it’s less likely I’ll have to scrap the strings. By taping them just above the neck pickup, and just below the nut – the strings remain in relative position to each other, and are much less likely to tangle. With the strings detuned and removed from the tuner posts, I can take off the scratchplate, and lift the control plate out onto the body. A cloth helps to protect the body underneath.
With the scratchplate off – I can unmount the neck pickup, and have a look at the wiring underneath. In the picture above, you can see the hardwired connection between the ground connection of the pickup coil, and one of the metal tabs which hold the pickup cover on. I don’t want to risk trying to unsolder the connection – especially at the coil connection – but it does look like I’ll easily be able to snip the jumper wire, and then clean up the pickup tab afterwards.
The pickup is unsoldered at the control plate. Both pickup ground leads are detatched from their grounding point on the back of the volume pot, and the white “hot” wire from the neck pickup is unsoldered from the selector switch. The pickup can then be completely removed from the body, by withdrawing the lead wires. This gives a little more space to work in, and makes the whole process much easier.
Using a pair of wire snips – I cut the jumper as close to the ground wire connection as possible. Then – with no way now for the heat to conduct up to the delicate coil wire – I can clean up the old solder connection to the cover tab. A new lead is then soldered onto the tab, and this will allow the pickup cover to be grounded somewhere else on the guitar. Without grounding – the cover may cause unwanted buzzing whenever it’s touched.
I’ve cut the new grounding lead just long enough so that it can be directly soldered to the copper shielding foil which lines the pickup cavity. It’s convenient enough to locate the attachment point directly below the pickup itself. The copper foil is contiguous with the rest of the shielding foil throughout the various cavities, and it provides another connection to the ground side of the guitar circuit. Once the solder connection has cooled – the ground is tested for continuity with a multimeter over the whole circuit.
With the pickup cover’s new ground checked and confirmed – the pickup leads are re-routed into the control cavity, and are re-soldered to complete the tone circuit. This time – the black wire is treated as the “hot” wire, and the white wire as the “ground”. The white wire joins the (black) ground wire from the bridge pickup, and is soldered directly to the back of the volume pot. The black “hot” wire is attached to the correct terminal of the 3-way switch.
The control plate is now replaced, with the internal wiring carefully looped inside, so it doesn’t unnecessarily stress any of the solder points. Pickup functionality can be quickly confirmed by gently tapping the relevant pickup with a screwdriver, when the selector is engaged in each of the switch positions. This confirms the pickups are functional – but I’ll still need the strings on, before I can properly check that the fix has worked properly.
The strings are laid back into place, and the loops formed by the strings around each capstan, returned to positions. It helps to guide the string ends into position around each post, as the strings are re-tightened, and I make sure that the newly wound wires don’t cross themselves as they turn around the tuning posts. Once the strings are re-attached – the guitar is brought to tune.
With the guitar now playable – I can use my Fender Mustang Micro amp, and a set of headphones to check that the polarity fix has worked, and that the pickups are now functioning as they should. The blended middle position now works with a similar strength of signal as each separate pickup – just as it should. There’s no unwanted noise or buzzing coming from anywhere – I’m calling that fix a success. With the scratchplate still off – I now have a chance to re-set the neck pickup height to exactly where I want it to be and then, after a quick wipe over with a soft cloth to remove any fingermarks, I replace the red plate by sliding it under the strings, and over the neck pickup. The scratchplate and control plate are screwed down, and that’s the buggy problem finally dealt with.