Jazz Bass w/Blender and Series/Parallel switching

[servant]

Hey guys and gals,

There are quite a few threads here with bits and pieces of what I wanted to do. I hope this thread helps others looking to do the same thing I want to do - that is to modify my Jazz Bass. I want a center-detented blend pot, a master volume with a push/pull switch for parallel / series, and a master tone.

Borrowing flateric's diagram from this thread (hope you don't mind, flateric!):
Blend Pot Q
I spun it inside MSPaint (I know, I know...) along with bits from fender.com/support wirings diagrams and came up with this:



How does this look? Did I get the orientation of the series and parallel sections of the switch correct, or are they upside down? If anything is amiss I will fix it up so I'm not spreading erroneous hints and allegations here.

Components are grounded by way of the steel control plate making contact with a shielded control cavity.

Thanks, folks!
servant




(Edited by sumgai to correct link to flateric's thread.)

[sumgai]

servant,

Your copy of ♭eric's diagram is good, but you connected the final output (the red wire) to the wrong terminal on the volume pot. The net effect is that the tone may or may not suffer, but for sure, the amplifier won't go dead-quiet when you turn the volume pot down to 1. Not an especially bad thing, but not good either, and fortunately, it's easy to correct.

Do these steps:

1) Move the red wire from the volume pot's center terminal to the right-most one, the one that has the violet wire going to the tone control. Leave that violet wire in place.

2) Disconnect the violet wire going from the tone control's center terminal to the output jack, and connect it to the volume pot's center terminal instead.

3) Connect ground to the left-most terminal of the volume pot. It shouldn't be implied or assumed, and after all, you do show the ground connections for the green wire and the capacitor, so just to be thorough......


Let us know how it comes out, eh? ;D


HTH


sumgai

[servant]

Thanks, sumgai,

How's this then?



If that covers all three of your corrections, I'll edit my first post.

And then I'll throw a wrench into the works! ;D

[ChrisK]

And then I'll throw a wrench into the works!

Perchance a wench?

a master volume with a push/pull switch for parallel / series,

Seems to infer knob down for parallel (normal) and up for series (turbo drive).

When the volume knob in your design is down (pushed), you select series and when the knob is up (pulled), you select parallel. If this is what you wanted, good is all.

Components are grounded by way of the steel control plate making contact with a shielded control cavity.

This actually means that components are grounded via the steel control plate and the shielded cavity is grounded by contact with same. The shielded cavity is an extension of the ground and not a proper signal carrying path.

Does this mean all signal grounds?, If so, I don't see an actual connection (other than a schematic symbol) for signal ground on the the blend pot and bridge pickup to anything. I might suggest using the volume pot lug that is already grounded.

I don't have issue with using the control plate for grounding the pot back shells, but I am fond of a soldered connection to the jack for both the output signal and the signal ground. I would use the grounded lug of the volume pot as the single point ground, and connect the jack and tone pot shell there also (you could just connect the tone cap to the jack ground since it's nearby).

[servant]

And then I'll throw a wrench into the works!

Perchance a wench?

I'll get back to you later...

When the volume knob in your design is down (pushed), you select series and when the knob is up (pulled), you select parallel. If this is what you wanted, good is all.

Good is not! That's what I was concerned about; thanks for catching that for me. I do want
Push/Parallel and Pull/TurboBoost/Series.

I would use the grounded lug of the volume pot as the single point ground, and connect the jack and tone pot shell there also (you could just connect the tone cap to the jack ground since it's nearby).

Do I need to ground the blend pot shell? I really figured that the steel control plate on these nullified the need for grounded pot backs... Wouldn't the combination of the two create a ground loop?

[servant]

How do you admins prefer to keep things? I want to remove the two, older images to avoid confusion,
keeping one Golden Image when I finally get it! On the other hand, you might prefer I keep them all
posted so others can see the progress and match images to the dialog.

Keep or delete?

***************************************************

I have measured from the output jack ground tab to:
- steel control plate = 0 ohms
- tone pot shell = 0 ohms
- blend pot shell = 0 ohms
- volume push/pull shell = 0 ohms
- output jack "ring" = 0 ohms

Do I need to add any wire grounds? (Other than adding the bridge ground, which has not been shown
in my diagrams but is in the cavity awaiting my return. I can solder that to the output jack ground tab.)

Here is an updated image showing the inverted push/pull connections.



In case violet looks too much like red, the only violet wire goes from the jack Hot to the center tab on
the volume pot.

[sumgai]

servant,

The preferred method is to leave history alone. That way, the posts that follow will make sense, as they refer to some particular thing in the drawing. If the drawing is gone, a future reader is left wondering WTH, and the poster is made to look like he's speaking with a forked tongue.

However, sometimes things go bump in the night, or there's a server space issue, or whatever...... images don't always survive these kinds of things, we understand. So, if you want/need/must remove an image, I ask only that you modify your post where it was displayed, and tell the reader that you removed it on purpose. You don't have to say why, that's not important. What's important is that you relieve the reader of anxiety as he says to himself "Is this image supposed to be gone, or is something wrong with my machine, or my internet connection?"

Please.

Thanks.



sumgai

[servant]

OK, folks. I've got this wired up to match the third diagram. She no worky the way I expect...

My tone control seems to act as a secondary volume control. Rolled all the way down, I lose about half the overall
volume. And, even at full-tilt, the overall volume is less than desired.

My series/parallel switch works as advertised. My blend pot has issues. It is a "proper" Fender blender, but I'm
not getting pickup isolation at the extreme ends.

Question: Are we sure that my blue wires from the blender to the switch go to the proper sides? I'm thinking they
are backward but they have been this way since diagram #1

. In other words, should all wires from the bridge
pickup go to the same side (left vs. right), and all neck wiring should go to the other? Those blue wires cross those
boundaries...

Here is the afore-mentioned wench: These are DiMarzio Jazz pickups, each one has two, end-to-end coils wired
in series - for a stock-sized humbucking configuration. I was going to ask "what else can I do with these four-wire
pups to enhance my option?" But I am not going to ask that - I just want "my" design to work.

While I work through this on my end (I really do want to learn...), have you got any thought?

EDIT: I went back to flateric's drawing, asking myself "Are you sure?" On his diagram he has that nice, large ground
symbol for the green/hot wire from the bridge pup. My diagram has a small gray dot on the back of the blender pot.
Guess what? I missed that!

So, I just alligator-clipped that wire to ground and voila: I get nice volume and tone out of the bridge pup (tone pot
works as expected; tone rolls off, not half the volume) - but only on about 1.5 - 4.7 on the blender pot. The signal
dies scratchily down at the extreme end. I've got some De-oxit spray cleaner so I'll shoot it in the blender, work
it back and forth, and see if it cleans up.

At the center detent there is no volume - my neck pup now is completely gone from the output! I'm actively
retracing every wire now...

[servant]

Fixed it!

Put the ground in on the bridge pup "hot" and also found that I had inadvertently reversed those two blue
wires I was just asking about.

Now both pickups sound at appropriate volumes. Although my blend pot is an official Fender Blender, I DO
find that there is a subtle volume drop at the center detent.

Series adds quite a mid-range punch that I will have to try out more through an amp. Fixed a fret buzz that
has bothered me since I got the bass (about six years ago).

Thanks, guys for all your help. Exalting coming up!