We're sure which way is ground?

[asmith]

I finished wiring a Les Paul copy I'd had on the backburner for more years than I care to admit. The scheme is a strange cousin of Borsanova's Twenty-Dual Mix scheme (JohnH's diagram here, for reference). Expectedly, it needs troubleshooting. A nasty dead spot when the input cable is angled a certain way, a faint signal where there should be a deliberate dead spot in the scheme.

But one of the strangest things that needs troubleshooting is that there's a heavy buzz when I'm not touching the strings. Now, the whole thing's shielded with two layers of shielding paint and I've multimetered the ohms out of it from every conceivable angle to make sure that all the cavities are shielded and that they're all electrically connected to the scheme's "ground" point. They are. On both counts. The thing is shielded. But still, guitar go brrrrrrrr.

Usually, at this point, a wise elder from the Council of GNutz would say, "asmith, sweet summer child, you've wired the input jack the wrong way round, classic asmith amirite" — but I know I haven't. I just wired the thing. Like, an hour ago. I looked input jack wiring up on Google Images and cross-referenced two results and said out loud to myself, "Hot to tip, ground to sleeve," and then soldered it up, screwed the input jack back into the body, and plugged it into the amp to give it a go.

Now I'm second-guessing myself. It's hot to tip, ground to sleeve, right?

[newey]

Aug 4, 2022 10:35:05 GMT -5 asmith said:

Now I'm second-guessing myself. It's hot to tip, ground to sleeve, right?

Yes, but sometimes it's hard to tell which lug is which, so make sure the lug you're calling the tip is actually the tip. Usually, the sleeve lug is uppermost, and you can see the metal connecting the lug to the sleeve/barral. The tip connection is usually lower, and sits betweeen two layers of phenolic (I think that's the stuff) insulating material.

But it could be a bad ground connection elsewhere, although if you've tested all the grounds, I dunno.

[unreg]

Hi asmith,

I clearly am NOT qualified to solve your problem, but have a few suggestions.

1.) My guitar amp experienced a NON-strong buzz due my pedal being plugged into a separate outlet, on another wall, from my amp… consequently, a ground loop appeared and made buzz. Simply use one outlet, if this may be a problem.

2.) Since your guitar electronics are a strange cousin for JohnH’s schematic, maybe you could present your strange cousin schematic to GNuts and they, maybe even JohnH, could troubleshoot your diagram’s other problems you mentioned.

3.) I have found that solving one problem often solves, or makes clear a path to solve, other problems, so maybe try removing another of your strange cousin’s faults and perhaps this buzz will disappear or become visible to remove.


p.s. Comically, and this is meant passively too, JohnH mentioned “Sleeve (ground)” and “Tip (hot output)” on his insanely-complex-to-me diagram you linked.

[asmith]

Aug 4, 2022 17:12:43 GMT -5 unreg said:

1.) My guitar amp experienced a NON-strong buzz due my pedal being plugged into a separate outlet, on another wall, from my amp… consequently, a ground loop appeared and made buzz. Simply use one outlet, if this may be a problem.

I'm plugging directly into the amp. 

2.) Since your guitar electronics are a strange cousin for JohnH’s schematic, maybe you could present your strange cousin schematic to GNuts and they, maybe even JohnH, could troubleshoot your diagram’s other problems you mentioned.

Sure:

3.) I have found that solving one problem often solves, or makes clear a path to solve, other problems, so maybe try removing another of your strange cousin’s faults and perhaps this buzz will disappear or become visible to remove.

Yep! I intend to rip it open and solve the jack issue; let's see if that fixes something.

p.s. Comically, and this is meant passively too, JohnH mentioned “Sleeve (ground)” and “Tip (hot output)” on his insanely-complex-to-me diagram you linked.

It's for folks like me

[cynical1]

I'm not qualified to answer any part of your question, but it's good to see you again.

Back in my hole...

HTC1

[sumgai]

Yeah, Ace, we still talk about your visit here, something like 10 years ago, I think it was. We usually keep it clean though, 'cause we've got a lot of newbies we don't wanna scare off. I'm sure you understand.

Seriously, dude, where are you holding court these days?





sumgai

[asmith]

Good to see you ('read you'?), Cyn and Sumgai. I'm still in Denmark. I was stuck in the hospitality industry for a long time after getting here, battling low wages, unforgiving work circumstances, and to mollify both of those things, a handful of bad habits taken to excess. I managed to start changing direction a few years ago. It's been slow and unsteady, but I think I'm headed on the right vector. The last ten months have been a really tough series of kicks in the teeth, though, for various reasons I won't get into.

This guitar actually had its wiring finished last July, but I didn't get an apartment-block-appropriate amp with which I could test the guitar until a friend of mine recommended the Positive Grid Spark this week. I picked one up second-hand, plugged in, and here we are.

I miss you both and wonder when I'll see you both again in person. Sorry about all the drinking the last time. 😬

[JohnH]

good to see you Mr Asmith!

a couple of thoughts...

When it's in parallel mode, and volumes turned right down, is it dead quiet and ohms reading very low to zero across the output jack?

Also, LP's have lots of wires up znd down to the switch. Are all those in braided or screened leads and are all those braids grounded?

[ashcatlt]

Pick up both your feet at the same time and you’ll probably find ground pretty quick.

[asmith]

Aug 6, 2022 15:43:15 GMT -5 JohnH said:

good to see you Mr Asmith!

Good to see you, John! Such a pleasure to have you respond to one of my posts again.

When it's in parallel mode, and volumes turned right down, is it dead quiet...

Yes: dead quiet.

...and ohms reading very low to zero across the output jack?

It reads about 20 ohms.

Also, LP's have lots of wires up and down to the switch. Are all those in braided or screened leads and are all those braids grounded?

Gooood catch! The humbucker wires are braided and grounded to the cavity shielding. The wires that head up to the selector switch and back down to the volume/tone-control cavity are unshielded. When shielding the body, I thrust the brush covered in shielding-paint as far as possible into the tunnels that link the cavities, but I can't say that those tunnels definitely got completely shielded.

Regarding the "dead spot at annoying angle" issue I mentioned at the thread's start: I realized that I'd painted the input jack cavity with shielding paint, but then, post-painting, I hadn't insulated the shielding from the cavity. This meant that the input jack, with the softest of prods, shorted against the surrounding shielding. 🤦 I just tweezered in some duct tape around the cavity walls, smoothed it flat with a screwdriver, then re-screwed the input jack back into place. This cleaned up the "dead spot at annoying angle" issue.

So, current status: the guitar still buzzes unless I'm touching the strings (or unless, as above in response to JohnH, both volumes are down).

Also, when the guitar is in the deliberate dead position — i.e., looking at the diagram in this post of mine further up in the thread: when the DPDT switch drawn center-top is 'thrown' the way it's drawn, putting the humbuckers in series, and when the SPDT "Rhythm / Treble" switch is 'thrown' in the opposite way that it's drawn, and is therefore in the "Rhythm" position — in that deliberate dead position, there's still a teeny-tiny very-faint signal reaching the amp from both humbuckers. I know both humbuckers are providing signal here because I can turn either pickup's volume control down and it quietens the signal somewhat, and when I turn both volume controls down, it stops the signal altogether.

EDIT to add:

Also, when I'm playing into a solid-state PositiveGrid Spark practice amp, after a while, it just kinda feels like I'm kinda acting as some kind of a capacitor. You know that feeling when you use someone else's laptop and it's plugged into the wall with a plug that only has two prongs? And you can kinda feel that you're completing some sort of circuit? It might just be my imagination, but I yanked the jack out of the guitar and continued playing unplugged and it stopped feeling like that. The weird thing is that I definitely connected the bridge, cavity shielding, and humbucker ground wires to a star point and then put a 630V 0.22uF 'ChrisK safety cap' capacitor in between that star point and the rest of the circuitry's 'ground'. My multimeter only measures ohms, volts, and amperes. Is there a way to find out if this is just in my head or not?

[newey]

Aug 10, 2022 14:15:49 GMT -5 asmith said:

Also, when I'm playing into a solid-state PositiveGrid Spark practice amp, after a while, it just kinda feels like I'm kinda acting as some kind of a capacitor. You know that feeling when you use someone else's laptop and it's plugged into the wall with a plug that only has two prongs? And you can kinda feel that you're completing some sort of circuit?

Hmmm. (meant both literally and figuratively). I'd look to check the wiring on the outlet you're plugged into as feeling "as if you're completing some sort of circuit" sounds more like a mains issue than a guitar issue. If you don't have an outlet tester, can you try pulling into a different circuit, see if the funny feeling disappears?

[asmith]

An update.

Aug 11, 2022 21:09:16 GMT -5 newey said:

I'd look to check the wiring on the outlet you're plugged into as feeling "as if you're completing some sort of circuit" sounds more like a mains issue than a guitar issue.

So, the PositiveGrid Spark comes with an ungrounded plug. That's basically how it comes out of the box. It's a solid-state amp with amp-modelling firmware inside. I can't change that. But the company is now selling a grounded power supply! A Scandinavian has made a short video comparing the grounded power supply's effect on the amp's noise with the un-grounded power supply's effect. I guess I'll have that grounded supply shipped out to me.

In the meantime, I got home my Fender Super-Sonic today and noodled around with it for half an hour. It's a grounded amp. Almost no buzz when I wasn't touching the strings. And almost no change when I then touched the strings. So it's likely not the guitar.

Regarding the circuit-completing feeling: I took resistance readings between strings and output lead hot, and between strings and output lead ground, and I got maximum resistance. There's no way any DC voltage is flowing from me touching the hardware. So, I think it was all in my head.

Did JohnH have any further thoughts after reading my answers to his questions asked in this reply of his?

[JohnH]

I'm all out of fresh ideas here. Except that with complex and series wiring, despite all best practices, a bit of buzz can get through depending on the amp.

[asmith]

All good! What did the test you asked me to do (parallel mode, volumes down) tell you/me/us?

[JohnH]

Aug 22, 2022 4:20:29 GMT -5 asmith said:

All good! What did the test you ask me to do (parallel mode, volumes down) tell you/me/us?

Well when you did that, the hot is connected to ground and it should be dead silent as it was. If not, then some ground in the guitar may have been not connected.

[asmith]

Aug 10, 2022 14:15:49 GMT -5 asmith said:

Also, when the guitar is in the deliberate dead position — i.e., looking at the diagram in this post of mine further up in the thread: when the DPDT switch drawn center-top is 'thrown' the way it's drawn, putting the humbuckers in series, and when the SPDT "Rhythm / Treble" switch is 'thrown' in the opposite way that it's drawn, and is therefore in the "Rhythm" position — in that deliberate dead position, there's still a teeny-tiny very-faint signal reaching the amp from both humbuckers. I know both humbuckers are providing signal here because I can turn either pickup's volume control down and it quietens the signal somewhat, and when I turn both volume controls down, it stops the signal altogether.

I figured out that this might be a selector switch that is maybe reaching its replacement date. Though I'm not sure that diagnosis gels with the success of what I decided to do about it, below.

I deliberately wanted a quiet dead spot in the 'Rhythm' position* in 'Both Humbuckers in Series' mode, but instead all I was getting in that position was lots of hum and a faint replication of the both-humbuckers-in-series signal. I realized that what was happening in the circuit I'd originally designed was that, in that position, a wire was running out from 'jack hot', up to the selector switch, and then back down to the 'control cavity,' where it consequently connected to a pole of the DPDT switch on the Bridge pickup's volume pot, which in the mode in question was thrown towards a lug connected to nothing. Essentially, I had created an antenna twice the length of the guitar's body, passing through the cavity-linking holes I'd not really shielded consistently, and connecting straight to 'jack hot'. Hence, brrrrrr. D'oh.

So I took a small bit of wire, and I connected that hitherto-unconnected lug up to the other lug on the other pole of that switch, because that lug was already connected to the circuit's ground. And, presto: after that, when in 'Both Humbuckers in Series' mode, and in the 'Rhythm' and middle positions on the selector switch, 'jack hot' connects to 'jack ground,' and the guitar is dead quiet.

I like this a lot, because it means I can use the selector switch as a kill-switch in this mode, and still use the Bridge or Neck pickups alone if I please, simply by turning each's volume all the way down.

So, the guitar's finished. I'll try and get hold of a mic and record a demo of its possible pickup combinations.

*The Rhythm Position is a great funk song title

[cynical1]

Aug 29, 2022 14:45:00 GMT -5 asmith said:

...*The Rhythm Position is a great funk song title

...or a form of birth control...

HTC1