1966 EB-2 Wiring - the PO screwed with this too much!

drbassman · March 16, 2008, 05:36:13 AM

Jules asked for this, so here it is. Not a pretty sight!

eb2 · March 16, 2008, 10:59:56 AM

I've seen a lot worse! Two 66 pots, and an interesting ground wire and the choke unhooked. Story of 80% of the Gibson basses. What is the problem?

drbassman · March 16, 2008, 12:50:33 PM

No problem. Jules asked for a shot of the guts when I got this rehab job into my shop. So, here it is. Certainly not entirely original. I love the Chinese jack. Ugh!

eb2 · March 17, 2008, 09:52:09 AM

OK, I get it. Well, I would look at it as being lucky that the choke didn't head for the trash. Chinese jacks may be so simple that they couldn't screw them up. But it looks like you can clean them up and re-wire to a Switchcraft jack easy enough.

Granny Gremlin · March 17, 2008, 12:42:38 PM

Why are there 2 tone caps?

drbassman · March 17, 2008, 01:03:51 PM

Quote from: Granny Gremlin on March 17, 2008, 12:42:38 PM
Why are there 2 tone caps?

I'd ask the PO, but I think he's brain dead.

eb2 · March 17, 2008, 11:15:48 PM

Maybe the Tele mod to keep it from mudding up as you turn the volume down? It is called a bleed cap - I forget the value, but it keeps the high end even. Tele people do it a lot.

drbassman · March 18, 2008, 05:34:42 AM

Quote from: eb2 on March 17, 2008, 11:15:48 PM
Maybe the Tele mod to keep it from mudding up as you turn the volume down? It is called a bleed cap - I forget the value, but it keeps the high end even. Tele people do it a lot.

Oh, I see. Well, I'll probably strip the entire harness down and rewire as close to specs as I can. I'm a fan of the mud myself!

Dave W · March 18, 2008, 09:17:20 AM

Isn't there supposed to be an .01 or .02 bleed cap?

drbassman · March 18, 2008, 07:47:47 PM

Don't know!

Dave W · March 18, 2008, 10:14:53 PM

I know at least some years of the EB-0 had an .01 bleed cap, not sure about the EB-2. Jake or Jules may know.

exiledarchangel · March 19, 2008, 01:52:31 AM

Quote from: Dave W on March 18, 2008, 10:14:53 PM
I know at least some years of the EB-0 had an .01 bleed cap, not sure about the EB-2. Jake or Jules may know.

That seems useless to me, you must have some highs to bleed, EB0's haven't got that problem, since they haven't highs, that's the good part about them!

eb2 · March 19, 2008, 09:18:20 AM

I don't believe older EB2s had that. I agree that it would be hard to preserve an even high-end tone when there wasn't a bucket of spit's worth to begin with. I suspect without the choke/3 way toggle mod it would not work as there is always a filter in the circuit.

chromium · March 19, 2008, 01:44:21 PM

I haven't tried the bleed cap trick, but I have no-load tone pots in my EB-2D, and even after the choke/3-way toggle mod, I'm hard pressed to discern any difference that they make - even when recording it through decent headphones or monitors. In hindsight, it seemed the equivalent of putting ballet shoes on a hippo.

Granny Gremlin · March 20, 2008, 10:40:08 PM

When I made that joke I assumed that the second cap was the leftover one from the choke, and it kinda looked like it was reconnected to something.

Now that's just me joking around, looking at where it's connected somewhat more seriously now, it really dosen't look like a bleed cap - those are connected to 2 terminals on the volume pot (parallel with a resistor usually) vs either connecting the backside of the tone pot to ground (standard shunt-to-ground tone cap) or in series with the signal from volume to tone pots, which would be a 1st order high pass filter.

... incidentally, using the dirty approximation of an online speaker crossover calculator (1st order Solen) and a starting frequency (for a quick what-if analysis) of 100Hz, I happened to get 0.04 uF for the cap value needed.

Take a look at an EB2 diagram. .... think that's a funny coincidence?

The other cap on it (the one used in the choke vs the tone cap) is 0.02. That would give you 200Hz as the -6db frequency instead. Proceeding to use this same website set for 2nd order Butterworth calculation, and using 200Hz as the start freq got me awful close to the componemt values of the original choke circuit (220, was pretty much on.... but remember, that for a 2nd order filter like the original choke, the calculated crossover point represents the -12db point, not -6).

I find that interesting. By luck or clever design, I dunno, but it appears that dude wired up a choke light.