No discernable difference between sound of neck and bridge pickups

Dr_Necessiter · June 2023

I've modded a couple of guitars and I'm trying to work out why the results are sub-optimal. In the first instance I swapped a couple of humbuckers for appropriately sized p90s and, as per the title, there's little to choose between them in terms of tone. I went with 500k audio taper pots (I volume, one tone) and a 0.022uf capacitor (can't now remember how I arrived at this rather than 0.047uf). Is the capacitor value likely to be the cause of this?

In the second instance, I bought a custom wiring harness for a strat with audio taper pots but the volume and tone controls are having no effect on the sound. Could I have killed the pots when soldering or might there be some other cause?

Many thanks for any ideas.

Sporky · June 2023

Second one sounds like short circuits somewhere.

Danny1969 · June 2023

Did you use a 220n cap instead of a 22n ?

2nd one sounds like ground connection missing on end of pot. The volume pot is supposed to be wired as a voltage divider so one end hot and one end grounded and centre lug is the output which is a division of voltage depending where the pot is positioned.
If the ground is missing one end then the pot will just act as a variable resistor and do little as a volume control

Dr_Necessiter · June 2023

Hi Sporky and Danny,

Thanks for the replies. The capacitor is the 0.022uf one listed here:

https://www.alegree.co.uk/collections/capacitors/products/paper-in-oil-vitamin-q-capacitors

The pickups are Alegree Desert Dews.

Dr_Necessiter · June 2023

I'll check for any loose connections on the strat.

SteveRobinson · June 2023

1. Is your switch faulty? Check that it's selecting each pickup correctly.
2. A picture would be a really useful aid to diagnosis

Sporky · June 2023

Danny1969 said:

2nd one sounds like ground connection missing on end of pot.

So it does!

I'd thought wiper shorted to hot end, but that'd go quiet all the way down.

Funkfingers · June 2023

SteveRobinson said:

1. Is your switch faulty? Check that it's selecting each pickup correctly.
2. A picture would be a really useful aid to diagnosis

3. In what guitar are the Alegree DD pickups installed? (More specifically, is the pickup selector switch a toggle type or a blade/lever type? These present different opportunities for wiring to go wrong.)

4. How old are the strings on the P90 guitar?

THINKS: One easy way to make metal covered pickups sound shite is to wire the single conductor + braided shield output cable backwards. This places the cover in the signal chain.

•

There are so many possible permutations of custom Stratocaster wiring harness that it is impossible to offer an opinion without seeing photographs of it.

ICBM · June 2023

The first one sounds like possibly a switch fault. It won’t be the caps, the value is not that critical.

The second one sounds like a missing ground - where does the ground wire from the jack go to? Is there a shielding foil on the pickguard? Are the three pot casings also linked with a wire? Is the ground terminal on the volume pot bent back onto the casing, or joined to it with a wire?

Dr_Necessiter · June 2023

Hi Steve and Funkfingers,

The switch is a toggle switch and it appears to be working as with a cable plugged in and a quick check with my multimeter I get different resistance readings as I toggle between the three positions. The strings aren't new but they haven't had a lot of play either - I don't have time to get the back off the guitar today but I'll do so tomorrow and post pictures.

As regards the strat, a quick check with the multimeter suggests that the volume pot is doing something but neither of the two tone pots is having any effect (no change in resistance as I roll the pot on and off). The harness is this one:

https://northwestguitars.co.uk/products/deluxe-7-way-wiring-harness-for-stratocaster-acitivate-all-3-pickups?variant=44796460302610

Again I'll post pictures tomorrow.

Thanks again to all for the replies.

Funkfingers · June 2023

Looking at the stock NWG harness photograph, they have chosen to run the black ground wire from the side of the volume pot rather than, say, the bottom of the DPDT switch case. This location can be tricky to solder onto without getting a cold/dry joint.

Check for continuity between the pot chassis and output jack socket.

•

As illustrated, the tone controls are lower = middle pickup only, upper = neck pickup up only. With the bridge pickup selected, neither tone pot is in circuit. Pity because it might prove useful on the bridge + neck combination.

If/when the NWG harness begins working correctly, IMO, it would be worth adding a jumper wire to selector switch so that the lower tone control acts on the bridge pickup.

SteveRobinson · June 2023

You won't see a any change in resistance at the jack when you turn a tone pot as a capacitor is in series with the variable resistor, making it effectively open circuit to direct current.

Odd that the push-pull is on the volume control as they can get in the way without the extra height.

I think you need to post decent pics of the actual installation for us to see.

Dr_Necessiter · June 2023

Thank you - will do.

BillDL · June 2023

Regarding the 2 x HB sized P90s with single volume and tone. What style of toggle switch have you fitted?

There are two different styles of open frame 3-way toggle switches, and the layout can be confusing on one if you are used to the other. I will assume you are not using a right-angle toggle switch designed for thin bodied guitars, which has all the connecting lugs on the same side.

On a SWITCHCRAFT switch the lugs for the pickup signal wires (shown as 1 and 2) are either side of the lug for the Ground/Earth (E). This lug usually sits higher than the live lugs. The common live output wire (L) that goes to the volume pot is on the OTHER SIDE of the switch and usually comprises two thin lugs that you squeeze and connect together.

When using single conductor wire with braided shield (ground), what people normally do is use the same type of braided wire for the common output from the switch, push the braiding back on both the pickup wires and Common output wire, then add a wire from the GROUND lug that they wind around the braiding of the three wires and solder them. Look at the YELLOW wire on the image below (taken from the resources of SixStringSupplies.co.uk and modified to suit your application):

Image: https://tfb-user-images.eu-central-1.linodeobjects.com/b951c6213fe39851f1bdc74fdb991d305dddae89bb53e70830

(Note: There are some terrific resources on the SixStringSupplies website that support some of the components and pre-wired looms that he sells: https://sixstringsupplies.co.uk/pages/guitar-wiring-diagrams and https://sixstringsupplies.co.uk/pages/guides-tutorials)

On a standard budget style 3-way toggle switch the lugs for the pickup signal wires (shown as 1 and 2 below) are either side of two thin lugs that you bend together and connect the common live output wire (L) that goes to the volume pot. The Ground/Earth lug is the solid thicker lug on the opposite side. When using single conductor wire with braided shield (ground), what people normally do is use a length of the same type of braided wire for the common output from the switch, push the braiding back on both the pickup wires and the common output one, then take a length of bare wire (insulated with heat shrink where it passes across the switch) from the ground lug on the other side of the switch, and wind it around the braid on the 3 cables and solder it. Same idea as with the Switchcraft switch, just using a different wire and lug.

You don't HAVE to wire the switches this way or even use a single conductor wire with external braid, but the pickups come with that type of cable and the methods above are certainly the neatest way to keep everything grouped nicely with a common ground.

Dr_Necessiter · June 2023

Thanks once again to all for the detailed replies. I’ve resisted adding photographs as you’d have to look at my appalling soldering and wiring. Having taken things apart a couple of possible answers suggest themselves:

On the Strat there’s no grounding from the right hand lug on the push-pull volume pot to the casing. It’s hard to spot on the wiring diagram and I missed it.

With regard to the other one, I did do something similar to the wiring in the switchcraft pot diagram but failed to include the live wire in the bundle which goes directly to the lug on the volume pot without being earthed. I’m assuming curing these issues will sort things out?

Funk fingers, with regard to your comment re the jumper wire on the pickup selector, there are already two as per Northwest’s diagram between poles A0 and B0 and between B1 and B2. Are you saying that a further one could be added?

Thanks once again.

Funkfingers · June 2023

Dr_Necessiter said:

Funkfingers, with regard to your comment re: the jumper wire on the pickup selector, there are already two as per Northwest’s diagram between poles A0 and B0 and between B1 and B2. Are you saying that a further one could be added?

I have not seen NWG's circuit diagram. Just the product images on their website.

Based on your selector switch terminal numbering system, B2 to B1 was what I was suggesting.

Some people seem to like B1 just for the bridge pickup, then, B2 linked to B3 to act on the centre and neck pickups. (I'm not keen on this arrangement myself - not even on HSS guitars.)

Dr_Necessiter · June 2023

Just a quick update - had the soldering iron out yesterday and that seems to have resolved the issues with both guitars. Thank you all once again for your help and advice and for being kind to a numpty.

Best regards,

Dr N.

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No discernable difference between sound of neck and bridge pickups

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