How do the Epiphone Jack Casady electronics work?

[Wasnex]

Seems right to me, but maybe something's so obviously wrong, I'm not seeing it. If you could clarify, I'd appreciate it.

Never mind ...My brain was apparently playing tricks on me .

I noticed that you reversed the order of the switch connections from the left most diagram to the center diagram. For some reason my brain saw the right most diagram, which is wrong (123,321)

The left diagram and center diagram will both give all of the proper impedance connections AFAIK, but the rotation of the switch is reversed.

My assumption is the center diagram starts in position 3 (50 ohms), and as you turn CW the impedance goes up to 250 ohms, and then 500 ohms. Keep in mind we are looking at the bottom of the switch, so CCW motion of the stator from this perspective is CW from the perspective of the knob. The left most diagram starts in position 1 (500 ohms), and as as you turn CW the impedance goes down to 250 ohms, and then to 500 ohms. Per the schematic, I am with you that the middle diagram would seem to be correct.

Also the chassis ground is missing on the left most diagram and you corrected this on the middle diagram.

 

[tomZbass]

Well, the Great TalkBass Timeout of '21 is over. Party time! LOL

For the simplified schematic, I added a detail panel for the output (+, -) of the transformer. It shows the shield/ground cross connection that's under the epoxy. For techs that are comfortable with reading and interpreting schematics, this is good to know info for troubleshooting.:
View attachment 4230225

For the Cadfael diagram, I moved grounds away from the output jack (thanks, @Wasnex). Major change was renumbering/rewiring impedance selector switch to match the rotation sequence on the knob plate (starting at full CCW, 50-250-500). Previous bad wiring gives, from full CCW, 500-250-50.:
View attachment 4230227

This last one is for fun, use it if you wanna. I always make diagrams of my current bass internals, pedals, aux equipment, etc.
So, during the timeout, I drew this one up as if I owned this bass. Just a simple left to right config.:
View attachment 4230259

Please check for mis-wiring I may have done, using the official source 97 Gibson schematic as reference. Artwork is set, no more changes will be made.

Grounding of components to be determined by whoever's repairing the circuit. In other words, connect the grounds to wherever's convenient. "Ground loops" aren't an issue in passive circuits. Ground loops are only possible in active/powered circuits where there are gain stages involved, or connecting two different powered pieces of equipment. In a passive bass or guitar, as long as you have a good continuous ground where everything eventually connects to the output jack sleeve, you're golden.

Here is my current wiring. Yes, I rewired the tone cap...again LOL. Notice that your B position wires are different from mine (my pink wire is your white wire). The green and white have been swapped. Is this because of a correction you have made to Cadfael's diagram? It's important to remember that I have no idea what I'm talking about and that I'm just the test monkey here who is willing to dismantle and rewire just for the sake of research.......and with the addition of an Orange Little Bass Thing mated to an 1x15 cab, I now have two very great sounding and completely different tone stacks to test the changes through.

 

[fig]

It's important to remember that I have no idea what I'm talking about and that I'm just the test monkey here who is willing to dismantle and rewire just for the sake of research

Man, I've seen you're actively learning the electric side of this stuff, and that's very cool. I believe for folk wanting to change the innards of their basses, they should learn at least the basics of schematic reading and be able to translate between schematics and diagrams.

I'm glad you changed-up your diagram. You added the ground wire to the selector switch pole, and now you have three selectable impedances.

Graded pop quiz time! Two questions. No time limit.

Now, don't get nervous. I'm easy on grading. I've heard Wasnex is a bit rough, though. I think the words I heard secondhand were, "He'll tear your soul apart.".

1. Is the wiring correct for proper impedance values (50, 250, 500) between the selector switch and transformer?

2. If correct, does the selection sequence match the following pic?:

Helpful hint: Maybe label the two poles (A,B) and the three throws (1, 2, 3). And the 1 thru 5 on the transformer, too.

Notice that your B position wires are different from mine (my pink wire is your white wire).

Yes, I'm glad you noted that in the original diagram.

Is this because of a correction you have made to Cadfael's diagram?

Yep. Had to do that to get the proper CCW to CW sequence marked on the knob's number plate (pic above).

 

[Wasnex]

I've heard Wasnex is a bit rough, though. I think the words I heard secondhand were, "He'll tear your soul apart."

Have a nice day anyway. I'll leave the thread in your capable hands. UNSUB!

 

[fig]

No, no NO! I was making a joke. That's why I put the smiley beside it. I did your name because you're the only other one, it seems, actively helping out.

I apologize for this. Wasn't the intent at all.

 

[tomZbass]

Man, I've seen you're actively learning the electric side of this stuff, and that's very cool. I believe for folk wanting to change the innards of their basses, they should learn at least the basics of schematic reading and be able to translate between schematics and diagrams.

I'm glad you changed-up your diagram. You added the ground wire to the selector switch pole, and now you have three selectable impedances.

Graded pop quiz time! Two questions. No time limit.

Now, don't get nervous. I'm easy on grading. I've heard Wasnex is a bit rough, though. I think the words I heard secondhand were, "He'll tear your soul apart.".

1. Is the wiring correct for proper impedance values (50, 250, 500) between the selector switch and transformer?

2. If correct, does the selection sequence match the following pic?:
View attachment 4235360

Helpful hint: Maybe label the two poles (A,B) and the three throws (1, 2, 3). And the 1 thru 5 on the transformer, too.


Yes, I'm glad you noted that in the original diagram.


Yep. Had to do that to get the proper CCW to CW sequence marked on the knob's number plate (pic above).

and so the way that mine is currently wired is not how it should be? and is therefor not sounding the way it should? it does seem and always has seemed (even when that ground wire was wrong at the switch) that my switch changes some gain perhaps but not really any tone.

 

[tomZbass]

Man, I've seen you're actively learning the electric side of this stuff, and that's very cool. I believe for folk wanting to change the innards of their basses, they should learn at least the basics of schematic reading and be able to translate between schematics and diagrams.

I'm glad you changed-up your diagram. You added the ground wire to the selector switch pole, and now you have three selectable impedances.

Graded pop quiz time! Two questions. No time limit.

Now, don't get nervous. I'm easy on grading. I've heard Wasnex is a bit rough, though. I think the words I heard secondhand were, "He'll tear your soul apart.".

1. Is the wiring correct for proper impedance values (50, 250, 500) between the selector switch and transformer?

Hard for me to answer because although I get the concept of the switch's relationships to the tone (on a new, correctly wired JCB) I don't really understand impedance.....and its relationship to tone. I've read in one of the many interviews with Jack and he kind of talked through it. And Ed Friedland did a good job of demonstrating it on Bass Player Mag's YouTube. This is why I am searching for what happens inside the transformer. Not so much where the wires go, but what do each of the taps achieve (tonally) and even how they achieve it (how a transformer works) and which wires are for which taps (which we will have figured out when we finally have the wiring correct). It is now obvious, as @wasnex has thought for a long time, that my bass was not wired correctly when I got it.

2. If correct, does the selection sequence match the following pic?:
View attachment 4235360.

I'm not sure what this question is intending to ask.....if the switch is wired correctly than the labels on the switch should do what Epiphone intended......

Helpful hint: Maybe label the two poles (A,B) and the three throws (1, 2, 3). And the 1 thru 5 on the transformer, too.


Yes, I'm glad you noted that in the original diagram.


Yep. Had to do that to get the proper CCW to CW sequence marked on the knob's number plate (pic above).

 

[tomZbass]

ok @fig here is my "as I bought it" and "working" diagrams

Clearly the "as I bought it" is out in left field.

My "working" is a mix of Cadfael and "as I bought it. I've got transformer 4 to B1 jumping to B2 and transformer 5 to B3. You're saying I should have transformer 4 to B3 and jumping to B2 and transformer 5 to B1?

 

[fig]

You're saying I should have transformer 4 to B3 and jumping to B2 and transformer 5 to B1?

I was a little unclear on the wording of the second part of sentence. If this is what you meant, then yes.
-Transformer 4 to B3. (you stated that)
-Transformer 5 to jumpered B1/B2.

But, with the switch numbering drawn in your diagram, it'll give you reverse order from the switchplate.:

Easy fix. Leaving Poles A and B where they are, swap the numbers 1 and 3 in each quadrant, move the jumper wire accordingly (1/2) and now do your wiring like you just posted. This'll give you 50, 250, 500 in correct switch plate order and you're golden.

But, if you like it the way it is, and don't wanna do the Gibson wiring, keep it as is. If these parts weren't so hard to access, I'd say owners should play around with different impedance combos. Might like them better than the Gibson selections.

Just for grins, I checked the "as I bought it" diagram. Yeah, it was wonk LOL.
Position 1 = guessing around 400 ohms.
Position 2 = guessing around 150 ohms.
Position 3 = 50 ohms (same as properly wired circuit)

 

[tomZbass]

I was a little unclear on the wording of the second part of sentence. If this is what you meant, then yes.
-Transformer 4 to B3. (you stated that)
-Transformer 5 to jumpered B1/B2.

But, with the switch numbering drawn in your diagram, it'll give you reverse order from the switchplate.:
View attachment 4236303

Easy fix. Leaving Poles A and B where they are, swap the numbers 1 and 3 in each quadrant, move the jumper wire accordingly (1/2) and now do your wiring like you just posted. This'll give you 50, 250, 500 in correct switch plate order and you're golden.

But, if you like it the way it is, and don't wanna do the Gibson wiring, keep it as is. If these parts weren't so hard to access, I'd say owners should play around with different impedance combos. Might like them better than the Gibson selections.

Just for grins, I checked the "as I bought it" diagram. Yeah, it was wonk LOL.
Position 1 = guessing around 400 ohms.
Position 2 = guessing around 150 ohms.
Position 3 = 50 ohms (same as properly wired circuit)

and so, how do transformers work?

 

[fig]

That's a broad question.

Are you wondering how they work in general or why one is being used in this circuit?

If you're wondering how, there's plenty of material online to answer that. I just did a quick look. The Casady transformer is a multi-tap transformer. Be sure to used that term. My in-depth theory stuff is 40 years old, so a little hazy LOL. I'll defer to someone with fresher theory knowledge to answer how transformers work. Here's a page for starters:
Multi-Tap Transformers – An Electrician's Guide to Single Phase Transformers

If you're wondering why, the purpose, a multi-tap transformer is being used? By changing, with the selector switch, the coil taps actively being used by the primary winding, it will change the output level and frequency response (the tone you hear) on the secondary winding (connected to output jack).

How does it do that? Well, you're back to learning how transformers work.

 

[Kbassface]

My JCB is in the shop as i type for a number of things but a dead pot being the main driver as she was dead in the water (shaft took a hit, bent and died, basically killing the whole circuit)...

One thing the we decided to do is to forego the OEM pots & put mil-spec linear taper pots in... this should cure the chronic crappy pot issues I've had since day one (she's on set #3 of OEM pots now) & yes I'll have to turn them a bit more than an audio taper but as long as they don't color the tone I'm more than fine with having what should be objectively better quality pots that will hopefully be the last ones ever needed....

and because I'm a glutton for punishment, i decided to see about a new transformer to ideally have a fresh circuit that will last me the rest of my life with this bass. Because I am a tenacious SOB when I want to be..... We are now waiting on a new transformer from Gibson... supposedly shipping to the local "authorized" shop this week , they're not the ones doing the work either, just using them as a pass thru for parts. (oddly enough Gibson treated it as a warranty part and my bass is a '02-03)

That said, I'm going to point the guys working on the bass to this thread (if he's not already here) for some reference etc...

but with a new transformer en-route... could it be possible / worthwhile to gently open up the older one, see what's behind the curtain and determine what's really going on and or have someone make a better quality / custom one? THinking of custom wound pups?

 

[fig]

but with a new transformer en-route... could it be possible / worthwhile to gently open up the older one, see what's behind the curtain and determine what's really going on

An attempt was made to dig inside. You might have a different approach, so give it a shot. Here's the thread. Pics start on post #145.
Tragedy strikes my Jack Casady... Any thoughts?

 

[Kbassface]

25172718[/URL], member: 29458"]An attempt was made to dig inside. You might have a different approach, so give it a shot. Here's the thread. Pics start on post #145.
Tragedy strikes my Jack Casady... Any thoughts?

thanks!!

 

[tomZbass]

That's a broad question.

Are you wondering how they work in general or why one is being used in this circuit?

If you're wondering how, there's plenty of material online to answer that. I just did a quick look. The Casady transformer is a multi-tap transformer. Be sure to used that term. My in-depth theory stuff is 40 years old, so a little hazy LOL. I'll defer to someone with fresher theory knowledge to answer how transformers work. Here's a page for starters:
Multi-Tap Transformers – An Electrician's Guide to Single Phase Transformers

If you're wondering why, the purpose, a multi-tap transformer is being used? By changing, with the selector switch, the coil taps actively being used by the primary winding, it will change the output level and frequency response (the tone you hear) on the secondary winding (connected to output jack).

How does it do that? Well, you're back to learning how transformers work.

Awesome! The link you, provided is awesome and now I get it, both the how and the why. Remember that I have (had) ZERO electronic engineering knowledge before I bought my poor, old, abused JCB. Now my brain is growing larger! Thanks @fig

 

[tomZbass]

So, this is what I've done and I've done it for all of us.......

I've purchased an as new JCB (Faded Pelham Blue from CME). I'll have it on 4/20!

I WILL pull the harness and (try to) create a schematic and draw a diagram of said harness as it has come from the factory.

It's time to get to the VERY bottom of this.

 

[fig]

So, this is what I've done and I've done it for all of us.......

I've purchased an as new JCB (Faded Pelham Blue from CME). I'll have it on 4/20!

I WILL pull the harness and (try to) create a schematic and draw a diagram of said harness as it has come from the factory.

It's time to get to the VERY bottom of this.

Man, that's awesome of you to do! There's a ton of us curious about this. And an excellent color choice, sir.

Interesting delivery date. But I wouldn't know nuthin' 'bout that...

 

[tomZbass]

Man, that's awesome of you to do! There's a ton of us curious about this. And an excellent color choice, sir.

Interesting delivery date. But I wouldn't know nuthin' 'bout that...

Delivery date............Dave who........Dave's not here.........Strawberry?

 

[thetragichero]

unless the transformer itself were dropped off a table, i wouldn't suspect it to go bad but if gibson replaced it for free then i guess why not?

 

[tomZbass]

Calling all Jack Players! Especially those who've purchased a 2020. I've just purchased a barely used Pelham Blue! The threaded inserts for the bridge seemed to be pressed into the body more than the other, older Ebony. Is this what yours look like? is this an Epiphone fix for these inserts pulling out? 2 days to return it if I don't like it your timely response requested....