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FDP Forum / Guitar Mods, Repairs, and Projects / EBO Bass 4-position "Tone Choke" value?

Pinetree
Moderator Emeritus
(with many stars)

NW Pennsylvania

Jun 17th, 2018 05:30 PM   Edit   Profile  

Rebuilding an EB-O bass for a customer that wants to revert to the early 70's 4-position rotary selector circuit.

As far as I've been able to research, the "tone choke" is a 1.5 Henry inductor, but I just can't imagine fitting one of these (linked below) in the control cavity.

A little help please.

Really?

Leftee
Contributing Member
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VA

Jun 17th, 2018 05:58 PM   Edit   Profile  

At least it wasn’t a flux capacitor. Those are a beyotch to install.

Pinetree
Moderator Emeritus
(with many stars)

NW Pennsylvania

Jun 17th, 2018 06:30 PM   Edit   Profile  

Dude, hows about saving the hilarity for Moe's?




Leftee
Contributing Member
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VA

Jun 17th, 2018 06:42 PM   Edit   Profile  

Grumpy today?

Pinetree
Moderator Emeritus
(with many stars)

NW Pennsylvania

Jun 17th, 2018 06:46 PM   Edit   Profile  

Sunburned.



Peegoo
Contributing Member
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Ooo that sandwich

is gonna get et
Jun 17th, 2018 07:53 PM   Edit   Profile  

Pinetree, the smaller 1.5H inductor is not a common item these days. Dan Torres used to sell them for a buck; his circuit (and others that were popular) was originally cooked up by Craig Anderton.

The small inductor is about 5/8" square.

I think Rothstein Guitars still sells them, but as part of a kit. They're getting them from somewhere. I'll bet if you call 'em they'll sell you one. Shipping will probably cost more than the part itself.



Here's one soldered onto a pot.

Leftee
Contributing Member
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VA

Jun 18th, 2018 06:48 AM   Edit   Profile  

This begs the question, was this sort of thing ever done in a guitar?

Peegoo
Contributing Member
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Ooo that sandwich

is gonna get et
Jun 18th, 2018 06:54 AM   Edit   Profile  

Sure.

- Passive midrange boost mod kits

- Reverend's bass contour control

- Hohner's Pro series mid control

...and many others

Peegoo
Contributing Member
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Ooo that sandwich

is gonna get et
Jun 18th, 2018 07:03 AM   Edit   Profile  

Mouser DOES stock it, but not as an inductor. They list it as a passive audio transformer, part number 42TL021-RC.

You use only the outer two leads of the primary winding for the 1.5H spec; the other four leads you snip off.

Wrap the thing with tape or stick a piece of heat shrink over it to prevent the clipped leads from grounding against anything in the cavity.

Click

here

(This message was last edited by Peegoo at 09:06 AM, Jun 18th, 2018)

hushnel
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North Florida

A Friend of Bill W.
Jun 18th, 2018 08:00 AM   Edit   Profile  

Wow, the man, I’’m guessing I may have an idea what the non-answered emails were about.

I searched around for about half an hour and came up with nothing.

Pinetree
Moderator Emeritus
(with many stars)

NW Pennsylvania

Jun 18th, 2018 08:01 AM   Edit   Profile  

Thank you.


(Here's the original style)

wrnchbndr
Contributing Member
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New Jersey

I'm back with the otters again
Jun 18th, 2018 08:59 AM   Edit   Profile  

Sounds a lot like a Varitone circuit

Peegoo
Contributing Member
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Ooo that sandwich

is gonna get et
Jun 18th, 2018 09:41 AM   Edit   Profile  

Very similar. The Gibson Varitone typically uses five caps, each with a 10M resistor in series, sometimes through a 1.5H inductor to ground, that switch in and out with the rotary knobber. I always thought this circuit was overly complicated.

Notice there's a 100K resistor across the switch too. I think the engineers stuck it there to prevent pops through the amp when rotating the Varitone knob between positions because the early rotary switches were the "break before make" contact type.

Because the inductor is not rolled in and out (with a pot) like with the mid contour control, its effect is fairly subtle. You could leave it out of the circuit and it would still work pretty well.

Here's the schematic for a 1961 Varitone.

wrnchbndr
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New Jersey

I'm back with the otters again
Jun 18th, 2018 10:14 AM   Edit   Profile  

I really liked the Varitone circuit in a number of guitars that I did. I put all of the caps on the rotary switch and it took up just a little more space than a regular pot. I used an audio transformer like you mentioned earlier. I put the varitone circuit in place of a tone cap off of a 250K pot (tone control). Wide tonal pallet but like any guitar with excessive switching options you spend more time fiddling with controls than playing the guitar.
I've seen the original wiring as posted by Pinetree in an EB1 and was immediately blown away by both the bass and its tonal pallet. Not a lot of people liked the EB1 but I sure did. The one I worked on had great mojo. But then I'm not really a bass player.

Peegoo
Contributing Member
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Ooo that sandwich

is gonna get et
Jun 18th, 2018 04:15 PM   Edit   Profile  

The engineers on the EB0 and EB1 knew their stuff.

They understood the importance of how magnetic reactance, coupled with a base plate of prefamulated amulite, improved panendermic transconductance through the semi-boloid slots in the stator.

More here.

Pinetree
Moderator Emeritus
(with many stars)

NW Pennsylvania

Jun 19th, 2018 07:27 PM   Edit   Profile  

I have a suspicion that the owner of this particular instrument is trying to restore it to its former glory, and perhaps try to sell it or pass it off as original.

Of course I just keep my mouth shut...



Peegoo
Contributing Member
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Ooo that sandwich

is gonna get et
Jun 19th, 2018 08:48 PM   Edit   Profile  

You're a trained monkey when you provide a service like this.

Unless you're aware of a crime being (or about to be) committed, ya ignores everything beyond the range of your soldering fumes and ya takes yer money :o)

Leftee
Contributing Member
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VA

Jun 20th, 2018 06:06 AM   Edit   Profile  

mmmmmmmmmmmmmmmmm

soldering fumes

Peegoo
Contributing Member
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Ooo that sandwich

is gonna get et
Jun 20th, 2018 09:26 AM   Edit   Profile  

I kinda like 'it. Smells like a campfire started with pine heartwood ("lighter knot," "fatwood," etc.).

If I smell and hear bacon frying though, it usually means I've mistakenly grabbed the hot pokey end of the soldering stick, and I do loud, ad lib rap flow.

Leftee
Contributing Member
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VA

Jun 20th, 2018 10:24 AM   Edit   Profile  

It is rather piney.

FDP Forum / Guitar Mods, Repairs, and Projects / EBO Bass 4-position "Tone Choke" value?




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