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Gibson EB3 Wiring diagram??

Gibson EB3 Wiring diagram??
« on: March 11, 2007, 08:55:59 AM »
I have what I believe ia a 1974 EB3 Walnut Bass. (Serial Number 530937)

The Rotary switch has been replaced by a three position toggle switch although I have the original switch with some wires attached. Can anyone help me with how to wire it or tell me where I can find a wiring diagram?

 :?  Thanks Guys/Gals..........Ant
Mature Bass guitarist - Off the road but looking to get "back on" with some Blues or Rock... before it\'s too late!!.

doom

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Gibson EB3 Wiring diagram??
« Reply #1 on: March 11, 2007, 09:13:15 PM »
Hello and welcome. The first question is whether the choke circuit is still intact in your EB3. There should be a coil in the cavity. Since you have a 74'ish bass it's hard for me to tell if it's a series 1 or 2 wiring (maybe someone else here knows). The date on this series 1wiring https://www.flyguitars.com/graphics/eb3-circuit.gif is dated 1974 but I don't believe that year is accurate since there's also a schematic of Thunderbird II and IV dated like that 1974 and those were non existant at that time. The series 2 wiring has a 1974 date written in the footnote so anyway I assume yours used to have the series 2 wiring.

I have the series 2 wiring as a PDF-file which you can have. Just pm your e-mail adress and I'll send it over to you. It would also be helpful if you could take photos of the electronics cavity and upload them on a free photo hosting site (for example photobucket.com) then either post links here to the photos or use the image function here so we can take a look at it.

Gibson EB3 Wiring diagram??
« Reply #2 on: March 12, 2007, 06:40:32 PM »
Anything post Slothead era (69-71) is a Series 2 - That diagram labeled as 1974 is a Series 1 despite the date on the schematic. Series 1 is 1961-68 (the Slotheads are a transition peiod and contain elements of both S1 and S2 circuits).  If unsure of the date of your bass, you can always check by looking for the choke coil in the control cavity (or in the case of a Slothead, just look at the headstock) - on a Series 1 this is inside a sealed metal box (sheilded), on a series 2 it is loose and unsheilded - the very same part as used in the Ripper (the thing that looks like 2 spools of thread on a screw in the middle of this pic):



click this for a bigger picture: https://www.flyguitars.com/graphics/ripper-wiringBIG.jpg

If the varitone switch has been replaced with a toggle, chances are that the choke coil (a humbucking inductor) was also removed - without this part it is pretty much pointless to go back to stock wiring - just keep the toggle (it was good enough for Jack Bruce). *** the pickups on your EB3 are most likely out of phase without this part, depending on how the modd was done; switch the leads on one of the pups to correct this (unless you like the out of phase sound, many people do) ***

The good thing about Series 2 is that there's a EB3 Wiring for Dummies type pictoral diagram out there.  I think that's the PDF Doom is talking about.  If not, I'll upload it later.

doom

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Gibson EB3 Wiring diagram??
« Reply #3 on: March 12, 2007, 07:52:47 PM »
Ah, Jake to the rescue. Now there's a big chance of sorting this issue out. I e-mailed Anthony both the pictorial and the series 2 schematics. I think pics of the cavity in question is on its way over here.

EB3 Wiring
« Reply #4 on: March 12, 2007, 09:03:16 PM »
Thanks you guys these Pics/Schematics are really helping.

The choke is missing by the way.  What did it do to the sound or phasing?.  I take your point about JB so I might leave it as a toggle. (Watched the Cream Albert Hall gig on DVD the other day) I was only thinking about restoring the rotary switch to keep it original.

Iv'e had this babe around three years and she sounds pretty fine anyway.


Ant :D
Mature Bass guitarist - Off the road but looking to get "back on" with some Blues or Rock... before it\'s too late!!.

Re: EB3 Wiring
« Reply #5 on: March 13, 2007, 05:06:43 PM »
Quote from: Ant Atkins
The choke is missing by the way.  What did it do to the sound or phasing?


The choke is a 2nd order High Pass (bass rolloff) filter.  It makes the mudbucker sound like the EB2/Rivoli clank as heard in 60s Britpop (same pup, same choke circuit, but in a differant bass). Personally I think it takes too much bass out, but it can be a useful sound in some situations.

2nd order filters, by nature, induce a 180 degree phase shift.  Gibson compensated for this by wiring the minibucker in reverse, otherwise, in pos 3 on on the EB3 varitone (both pickups, choked mudbucker), the pups would be out of phase. This is why when using both pups on an EB2D, they will be out of phase when the baritone switch is off (in phase when on).

I prefer the in phase sound, so I would check that the wires on one of the pups in your bass are reversed (doesn't really matter which one), i.e the outer shield going to 'hot' - usually one of the terminals on the vol/tone pot - and the inner conductor going to ground (usually a pot casing).

Eb3 Wiring
« Reply #6 on: March 13, 2007, 07:01:21 PM »
Wow.......thanks for all that!.  I did not know about the choke at all!.  Ok I will check to see if PU's are in or out of phase.........I  prefer the idea of not too much Bass roll off so don't think i'll be looking to replace the choke.  She sounds pretty good to me as is at the mo. I will get back to you let U know how it is.

Ant
Mature Bass guitarist - Off the road but looking to get "back on" with some Blues or Rock... before it\'s too late!!.

EB3 Wiring
« Reply #7 on: March 14, 2007, 08:12:23 PM »
Well both PU were wired with the Screen going to the common earth and the centre (Hot) wire to the related pots.  So I reversed the Mudbucker (Hot to earth) and I like the result!!.........But was picking up earthing "noise" unless I touched the mb, when it stopped.  Noise is like a single coil PU strat sizzling in front of an amp..  Perhaps I should reverse the bridge PU instead?.  Anyway I've gone back to how it was until I hear from you guys. The Caps are fitted but no resistor/s.

Ant
Mature Bass guitarist - Off the road but looking to get "back on" with some Blues or Rock... before it\'s too late!!.

doom

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Gibson EB3 Wiring diagram??
« Reply #8 on: March 14, 2007, 11:18:28 PM »
Best way for getting rid of the hum would be trying reversing the wires at the pickup end. Otherwise the casing and cover are not connected to ground. I'm glad it worked out for you soundwise.

Gibson EB3 Wiring diagram??
« Reply #9 on: March 15, 2007, 04:51:22 PM »
Not sure what you mean by that Doom, but reversing the wires at the pup end, now that the pot end has been reversed, will bring us full circle to being out of phase (litterally, lol).

I'd try one of the following:
- put the mudbucker wiring back to stock and reverse the bridge pup instead (may have same issue with this pup tho, )

- try grounding the mudbucker with a third wire from the mud chassis to a pot casing - just like the bridge ground.... might get a ground loop.... try it with alligator clips first

doom

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Gibson EB3 Wiring diagram??
« Reply #10 on: March 15, 2007, 11:27:15 PM »
What I really meant was reverse back at the pot end and then reverse the winding wires from the coil. This might be tricky though. I've never taken a mudbucker apart and reversing this way could be ruining the tiny wire. The risk here is overheating the insulation. Would'nt a third wire to the casing shortcut the circuit at this point Granny? If Gibson had used a shielded two lead cable this thing would have been easier with both coil ends insulated from the casing and only the shield connected to ground.

Gibson EB3 Wiring
« Reply #11 on: March 16, 2007, 05:39:31 PM »
Thanks Doom & Granny............

Will take a look at the bridge PU.....see if I can reverse this & ground the cover/case.

Ant
Mature Bass guitarist - Off the road but looking to get "back on" with some Blues or Rock... before it\'s too late!!.

eb3
« Reply #12 on: June 18, 2011, 12:23:00 AM »
I got a choke -- ferrite rod with copper winding -- from an old amp circuit and wired it in parallel across the positive of my modern Gibson SG bass.
The sound is really good, almost like an octaver, kind of two notes mixed together.

Gibson EB3 Wiring diagram??
« Reply #13 on: June 19, 2011, 03:24:39 PM »
Just an idea...the wiring was missing entirely on my EB3...and so I had to start from scratch...wired the bridge pickup to a volume pot positioned in the hole where the rotary switch used to be; fitted a black oversize washer+a chicken head knob.The neck pickup volume is wired to a pot in the usual position,and the output from the "dummy" switch is also added..this enables me to blend the bridge pickup in/out of the neck by rotating the chicken head,I have only one master volume,you could add another,using a stacked pot as a pan pot in the switch position....not for everybody,but a quick and cheap way of getting you up and running that looks original...otherwise SG wiring with a toggle switch works just fine!! Given EB3 wiring is rather complex,it makes you wonder if Jack Bruce`s crew gave up fixing it!!! Good Luck...

Gibson EB3 Wiring diagram??
« Reply #14 on: June 19, 2011, 07:38:32 PM »
In what few pictures I have of Jack Bruce and EB3s it looks like he only used the bridge pickup, pics of Andy Fraser seem to show the same.
Pete

 

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