Bridge pickup gets quiet and tinny when neck pickup is connected

[Meyatch]

New bass build, will probably post about it after I get this figured out:

Played a gig friday with it, went fine, played a gig saturday, lost signal, or at least got really quiet., sunday everything seemed fine. I don't know what happened. I put a giant volume knob on it, might have just turned it down. You'd think I'd have checked that before I switched basses, but who knows, sometimes you forget to do obvious things in the heat of the moment. I decided I was going to install a control bypass switch so I could flip that if I have any problems, or use it to set a tone and then switch to a different tone quickly.

Get everything wired up, everything appears to work, but my bridge pickup is very quiet and has no bass.

Bass was wired volume/blend/tone. I can't say for sure that it didn't have this problem before I put the bypass switch in. I've moved stuff around, making and breaking connections. This is immediate and noticeable issue. Right now its wired with the hots from the pickups and output jack wired together, and the grounds from the pickups, bridge, and output jack wired together. If I connect everything but the hot from the neck pickup, it sounds fine, as soon as I touch the hot from the neck pickup to the hot from the bridge and output jack, the bridge gets tinny. The neck pickup always sounds the same, with the bridge connected or not.

This is 100% an electrical problem, its very noticeable just tapping on the pole pieces. Pickups are Fender Ultra Noiseless Jazz Bass, stacked humbuckers. The pickups only have hot and ground. When all the electronics were hooked up the bridge pickup sounded that way with the bypass on or off, and when panned to only the bridge pickup. The controls are not in the usual place and wires from the pickups and output jack go through channels to the controls. I definitely know which wire is hot form the bridge and the neck, I don't really know which ground is which.

Trying to run some google searches and I'm just getting stuff about pickups out of phase or the height being off or whatever. This is definitely a wiring problem. Does anyone know what I'm doing wrong?

 

[HardNHeavy]

i was gonna say "out of phase", same thing happened on one of my PJ basses, until i switched the hot wire from the bridge pickup around, but since you have googled it and you have your bass (jazz bass)? wired differently with a bypass there's obviously something askew. It's probably something simple too..Wish i could be of more help..someone will come along with more info.

 

[Meyatch]

Ok, I just reversed the leads from the bridge pickup just to make sure. Same thing, bridge sounds full when its connected, connect the neck pickup and the bridge gets tinny. Neck pickup sounds full either way.

 

[Meyatch]

with both pickups wired in series straight to the jack, the bridge pickup sounds fine.

 

[ardgedee]

Can you post photos? It's hard for anybody to diagnose your work if they can't see it.

One thing you can try is diagram the whole circuit as it currently exists, from pickups through controls to jack. Do it with pen and paper. It's a way of reviewing how you built the circuit without getting distracted by appearances.

 

[Meyatch]

Can you post photos? It's hard for anybody to diagnose your work if they can't see it.

One thing you can try is diagram the whole circuit as it currently exists, from pickups through controls to jack. Do it with pen and paper. It's a way of reviewing how you built the circuit without getting distracted by appearances.

I mean, that’s why I have simplified everything. There really is no need for diagrams or pictures.

When the hot from the bridge pickup is connected to the output jack, and the jack ground, bridge ground, bridge pickup ground, and neck pickup ground is connected to each other, the bridge pickup sounds fine. As soon as I touch the hot from the neck pickup to the connection between the bridge hot and output jack, the bridge gets tinny and the neck sounds fine.

I realize that “something” is wrong, but it’s not a loose wire or bad connection on the bridge pickup, or it wouldn’t work fine without the neck pickup.

 

[ardgedee]

I mean, that’s why I have simplified everything. There really is no need for diagrams or pictures.

When the hot from the bridge pickup is connected to the output jack, and the jack ground, bridge ground, bridge pickup ground, and neck pickup ground is connected to each other, the bridge pickup sounds fine. As soon as I touch the hot from the neck pickup to the connection between the bridge hot and output jack, the bridge gets tinny and the neck sounds fine.

I realize that “something” is wrong, but it’s not a loose wire or bad connection on the bridge pickup, or it wouldn’t work fine without the neck pickup.

If it's not working and you need help, letting other people see it (or rendering it in a different form for your own eyes) is the best way to be sure you're not overlooking something.

Otherwise we only have your words to go by, and I'm sure you're trying to be as honest as you can, but all people can do with a text description is make suggestions based on their own imagination of the problem.

 

[JimmyM]

I mean, that’s why I have simplified everything. There really is no need for diagrams or pictures.

When the hot from the bridge pickup is connected to the output jack, and the jack ground, bridge ground, bridge pickup ground, and neck pickup ground is connected to each other, the bridge pickup sounds fine. As soon as I touch the hot from the neck pickup to the connection between the bridge hot and output jack, the bridge gets tinny and the neck sounds fine.

I realize that “something” is wrong, but it’s not a loose wire or bad connection on the bridge pickup, or it wouldn’t work fine without the neck pickup.

You really should post a pic anyway. Words can only describe so much and you might have missed something that escaped your attention.

 

[Meyatch]

OK, I'm skeptical this relays any new information, but I hope someone sees something I'm overlooking.

white wire = neck pickup hot
black wire/white elec tape = neck pickup ground
red wire = bridge hot
black wire = bridge ground
blue wire = output jack hot
green wires = bridge ground and output jack ground

I realize these may not be the 100% best connections. Some pics may not even show metal on metal, I was more concerned with the wires going where they were supposed to for a picture than having good contact. Everything that's supposed to make contact is. I can jiggle the wires, etc while tapping.

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series wiring, both pickups sound full when tapped

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bridge pickup connected, neck not connected. bridge pickup sounds full, neck pickup makes no sound.

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both pickups in parallel. neck pickup sounds full, bridge pickup sounds tinny

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super professional wiring diagram



Thanks for any help.

 

[Meyatch]

ok, no resolution, but potentially some more information.

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With the wiring harness hooked up to the output jack ground, bridge ground, and bridge pickup ground, and the output jack hot to the output of the wiring, and the bridge pickup hot connected to the blend pot, panned to the bridge pickup, I get tinny bridge sound.

With the wiring harness hooked up to the output jack ground, bridge ground, and bridge pickup ground, and the hot of the bridge pickup wired directly to the hot of the output jack, I get full bridge pickup sound.

 

[Meyatch]

ok, I took the pickups out of the bass and connected them directly to cable with alligator clips. Both normal, and backwards, and with the neck normal and the bridge backwards. Its exactly the same every time. The bridge pickup sounds normal until the neck is connected, then the bridge pickup is tinny. I really don't have any idea what other trouble shooting I could possibly do.

 

[ardgedee]

It's a little hard to tell what's going on since you have loose wire ends and some mid-run joints that look like unsoldered hooks. I assume you're aiming for a generic VBT circuit and that you're slipping the bits of shrinkwrap over the hooks to avoid grounding against the shielding but they're still adding many points of failure risk.

My first thought would be to desolder everything, remove all the wire (except the pickup leads) and start out with new wire that you can cut to useful lengths, get rid of the hooks and have a cleaner compartment. Sometimes if debugging a circuit with a lot of connections is taking a long time it's easier to start over with a simpler circuit and then add elements one by one until the problem reappears.

 

[Meyatch]

I've learned a lot of stuff over the years at Talkbass. This was not one of those times. Its sort of like when your internet doesn't work, and you've tried everything and you know the problem is on their end, and the first thing they do when you call them is tell you to restart your modem.

The question I meant to ask was "What would cause this behavior in pickups that were properly wired?"

Turns out the answer was a bad pickup, and not the fact that I didn't solder connections and desolder them while I was trying to figure out the problem.

Everything works now with a new pickup.

 

[JimmyM]

I've learned a lot of stuff over the years at Talkbass. This was not one of those times. Its sort of like when your internet doesn't work, and you've tried everything and you know the problem is on their end, and the first thing they do when you call them is tell you to restart your modem.

The question I meant to ask was "What would cause this behavior in pickups that were properly wired?"

Turns out the answer was a bad pickup, and not the fact that I didn't solder connections and desolder them while I was trying to figure out the problem.

Everything works now with a new pickup.

Ya, that was everyone else’s fault for not knowing your pickup was broken after you said that wiring them up directly to the jack sounded fine.

 

[Meyatch]

No I said wiring the bridge pickup to the jack sounded fine and wiring both to the jack the neck sounded fine and the bridge sounded thin.

Obviously it’s not anyone’s fault, but it is a quirk of forums and the internet in general to invent a problem you do know how to give a response to rather than say you don’t know.

 

[Pep]

I didn't bother to read all of the replies, but here's something I've experienced. I have several Jazz basses and don't care for the separate volume controls. I prefer volume, blend, tone. Due to that I've had to rewire them. I tried it several times and ended up with that you have.
It wasn't until I started doing this. I made sure I was using a 250kΩ volume pot and then installed a 500kΩ/500kΩ mono blend pot and everything works perfectly. A 250kΩ/250kΩ mono blend pot will not work properly.

 

[mrperkolator]

I've learned a lot of stuff over the years at Talkbass. This was not one of those times. Its sort of like when your internet doesn't work, and you've tried everything and you know the problem is on their end, and the first thing they do when you call them is tell you to restart your modem.

The question I meant to ask was "What would cause this behavior in pickups that were properly wired?"

Turns out the answer was a bad pickup, and not the fact that I didn't solder connections and desolder them while I was trying to figure out the problem.

Everything works now with a new pickup.

My initial thoughts were to phasing. Since they’re “noiseless” I believe they have two coils each pickup. Given a new pickup fixed it, I’d bet money the bridge was wired incorrectly internally (you only saw external). The incorrect internal wiring caused your phasing issues (it sounds exactly like phasing issues).

Only non-invasive way of “looking inside a pickup” is using the green mag paper or using a cheap compass to check polarity. Neither would help huge in this case, but maybe the polarity check might have helped.