Pots behavior in Series-Parallel J-Bass

[DoughBoy1917]

I could never get the sound I've been searching for out of my plain J-Bass so I decided to do the series/parallel mod after looking around here on TalkBass and elsewhere, reading how bassists everywhere love this relatively simple mod.

I exactly followed the Seymour Duncan wiring diagram. Here's what I got as a result...

1) The tone control is no longer a tone control, it's a bizarre rotary on-off switch, i.e., turn the pot all one way and no sound, then full over the other way, the sound comes on. Nothing tonally or otherwise happens in between these two points, no matter the position or setting of the other two pots.

2) Although the bridge pot seems to vaguely control the bridge pick up volume, it doesn't seem to be adding anything to the mix, i.e., no blending between the pick ups like before. The characteristic bridge pickup twang is very low, regardless what position the neck (switch) pot is in.

3) The neck switch pot seems to be doing everything. Push or pull it, renders a vastly different sound from extreme loudness, to a weaker, less refined version of what the J-Bass was before, without the pickup blending flexibility.

Are the pots doing what they should be doing? Is this what is supposed to go down after this mod?

Very confused and have to say, a little disappointed.

Any help is greatly appreciated. Thanks.

[Emibass]

I did this to my jazz though I came back to stock. As about the pots, the bridge volume is out of the circuit when series mod is done. The tone should act as before so I belive you did something wrong.

IMHO

[St Drogo]

When you put the pups in series, they both have to be on, so one volumecontrol would not be operational. In this case the bridge one.

As for the tonepot issues, I don't know man...

[DoughBoy1917]

Should the tone pot be doing what it normally would do in both modes?

[St Drogo]

I think it should. When you put two singlecoils in series, you are essentially making them into one big humbucker. That should not make the tonepot behave as you describe.

[wvbass]

Originally Posted by DoughBoy1917

I could never get the sound I've been searching for out of my plain J-Bass so I decided to do the series/parallel mod after looking around here on TalkBass and elsewhere, reading how bassists everywhere love this relatively simple mod.

I exactly followed the Seymour Duncan wiring diagram. Here's what I got as a result...

1) The tone control is no longer a tone control, it's a bizarre rotary on-off switch, i.e., turn the pot all one way and no sound, then full over the other way, the sound comes on. Nothing tonally or otherwise happens in between these two points, no matter the position or setting of the other two pots.

2) Although the bridge pot seems to vaguely control the bridge pick up volume, it doesn't seem to be adding anything to the mix, i.e., no blending between the pick ups like before. The characteristic bridge pickup twang is very low, regardless what position the neck (switch) pot is in.

3) The neck switch pot seems to be doing everything. Push or pull it, renders a vastly different sound from extreme loudness, to a weaker, less refined version of what the J-Bass was before, without the pickup blending flexibility.

Are the pots doing what they should be doing? Is this what is supposed to go down after this mod?

Very confused and have to say, a little disappointed.

Any help is greatly appreciated. Thanks.

Clearly, you have something not quite right. When in parallel, you should have the same jazz bass controls you have always had. In series, one volume pot should have no function.

Can you post the schematic you followed (or a link to it on the SD site) and pictures of your implementation of it?

[DoughBoy1917]

Originally Posted by wvbass

Clearly, you have something not quite right. When in parallel, you should have the same jazz bass controls you have always had. In series, one volume pot should have no function.

Can you post the schematic you followed (or a link to it on the SD site) and pictures of your implementation of it?

http://www.seymourduncan.com/support...c=jass_bass_sp

Followed it to the "letter". The switch pot (currently in the neck position) is the standard from Stewart MacDonald. The bridge pot is the original one as is the tone pot.

Thanks for taking the time.

[DoughBoy1917]

Correct me if I'm wrong here, but what if I use the former neck pot to replace the tone pot? They're both 250k, although I can't fathom what could go wrong with a pot. The capacitor that came with the bass is listed as 473K 100v, and is not a ceramic disc .1 or .05 like in the seymour duncan diagram. I can't imagine this being the problem, but I can run to a radio shack and grab one or another.

This is now a mission.

[BassLife77]

Originally Posted by DoughBoy1917

I could never get the sound I've been searching for out of my plain J-Bass so I decided to do the series/parallel mod after looking around here on TalkBass and elsewhere, reading how bassists everywhere love this relatively simple mod.

I exactly followed the Seymour Duncan wiring diagram. Here's what I got as a result...

1) The tone control is no longer a tone control, it's a bizarre rotary on-off switch, i.e., turn the pot all one way and no sound, then full over the other way, the sound comes on. Nothing tonally or otherwise happens in between these two points, no matter the position or setting of the other two pots.

2) Although the bridge pot seems to vaguely control the bridge pick up volume, it doesn't seem to be adding anything to the mix, i.e., no blending between the pick ups like before. The characteristic bridge pickup twang is very low, regardless what position the neck (switch) pot is in.

3) The neck switch pot seems to be doing everything. Push or pull it, renders a vastly different sound from extreme loudness, to a weaker, less refined version of what the J-Bass was before, without the pickup blending flexibility.

Are the pots doing what they should be doing? Is this what is supposed to go down after this mod?

Very confused and have to say, a little disappointed.

Any help is greatly appreciated. Thanks.

that tone pot thing happened to me and I discovered I had all the ground wires going to the same ground. I had to cut some ground wires and rewire according to the signal path - pickups to switch to volumes to tone pot to output jack. when I short circuit that path the pots don't act right

[wvbass]

Originally Posted by DoughBoy1917

http://www.seymourduncan.com/support...c=jass_bass_sp

Followed it to the "letter". The switch pot (currently in the neck position) is the standard from Stewart MacDonald. The bridge pot is the original one as is the tone pot.

Thanks for taking the time.

Ok. I used the same circuit when I wired my Jazz for series/parallel. (Not the Seymour Duncan sketch, but the same circuit none the less.) This circuit does not have the behavior you describe. That leaves two possibilities that I can think of: 1) you have made a mistake that you just don't see, or 2) you have a faulty component (or components) or have something shorting out somewhere.

Lets take it one problem at a time:

Originally Posted by DoughBoy1917

1) The tone control is no longer a tone control, it's a bizarre rotary on-off switch, i.e., turn the pot all one way and no sound, then full over the other way, the sound comes on. Nothing tonally or otherwise happens in between these two points, no matter the position or setting of the other two pots.

This sounds to me like you might have a damaged or bad capacitor. If the capacitor is shorting out to ground, then when it is all the way one way there will be no sound. All the way the other way will produce sound, but you will have no tone controls. I suggest replacing the capacitor. You can get a replacement at Radio Shack for a dollar or two.

Originally Posted by DoughBoy1917

2) Although the bridge pot seems to vaguely control the bridge pick up volume, it doesn't seem to be adding anything to the mix, i.e., no blending between the pick ups like before. The characteristic bridge pickup twang is very low, regardless what position the neck (switch) pot is in.

According to the diagram, when the switch is UP (series) the bridge volume will have no function. You aren't clear whether the bridge pot still controls the bridge pickup in both switch positions; more info is needed here.

Originally Posted by DoughBoy1917

3) The neck switch pot seems to be doing everything. Push or pull it, renders a vastly different sound from extreme loudness, to a weaker, less refined version of what the J-Bass was before, without the pickup blending flexibility.

"Extreme loudness" may be a properly working series mode. You may have a problem with the normal parallel mode. If your capacitor is shorted and messing with your tone pot, I'm not sure what side effects that might have volume-wise, but I would think it could only serve to make the bass quieter, or "weaker."

You could temporarily remove the capacitor from the circuit altogether. There would be no tone controls, but you could get the rest of the circuit working without it and then replace the capacitor later.

Plus, once the capacitor is disconnected, you should be able to do a DC continuity check with a multimeter to see if the capacitor is shorted.

[wvbass]

Originally Posted by BassLife77

that tone pot thing happened to me and I discovered I had all the ground wires going to the same ground. I had to cut some ground wires and rewire according to the signal path - pickups to switch to volumes to tone pot to output jack. when I short circuit that path the pots don't act right

I have tried and tried to understand what you are saying here and I just can't figure it out. There is only one ground, regardless of where you connect to it. "All the ground wires going to the same ground" sounds like star grounding, which some here are a big fan of. Personally, I've never found it to be necessary in a bass's control cavity, but it certainly won't hurt anything.

What am I not understanding about what you are saying?

[bassbenj]

Originally Posted by DoughBoy1917

Correct me if I'm wrong here, but what if I use the former neck pot to replace the tone pot? They're both 250k, although I can't fathom what could go wrong with a pot. The capacitor that came with the bass is listed as 473K 100v, and is not a ceramic disc .1 or .05 like in the seymour duncan diagram. I can't imagine this being the problem, but I can run to a radio shack and grab one or another.

This is now a mission.

The tone control should not be acting this way. Something has to be shorted somewhere! Look closely for shorts! The Seymour Duncan diagram looks good to me if you followed it "to the letter".

As a test lift the capacitor wire from the pot terminal. If the pot now does nothing at all that means it's OK. If it still acts like an on-off switch it is bad! If the disconnected cap pot does nothing then it is likely the cap is shorted. Your cap is .047 mfd. (473k means 47 and 3 zeros pf = .047 ufd) You can try any cap that size or similar to see if that's the problem. Make sure solder hasn't slopped somewhere creating a short!

Good luck on your mission!

[BassLife77]

Originally Posted by wvbass

I have tried and tried to understand what you are saying here and I just can't figure it out. There is only one ground, regardless of where you connect to it. "All the ground wires going to the same ground" sounds like star grounding, which some here are a big fan of. Personally, I've never found it to be necessary in a bass's control cavity, but it certainly won't hurt anything.

What am I not understanding about what you are saying?

a ground wire that went to the switch was also connected to the ground of one of the pots. when I severed that connection everything worked fine. I'm new to bass modding and electronics so I can't explain in detail why it worked. I realized there has to be a straight signal path from the pickup to the output jack without any shorts

[DoughBoy1917]

Went to Radio Shack, got a .1 cap (they didn't have .05). Came home, replaced the old one and BAM...everything is hunky dory.

***!

I shoulda' known. I got this used J Bass super cheap. The original owner mistreated it but the neck was fine and it played ok. When I finally removed the plate for the first time ever, it revealed a sloppy mess...solder everywhere, frayed wires. I removed and cleaned everything, starting from scratch, wiring per the diagram, using the same parts when possible. It had been playing before right?

Then the shenanigans started.

Thanks all!