Basic question: read continuity to ground through a capacitor?

Thread Starter

kharrisma

Joined Dec 9, 2019
3
Hi Forum Folke,

Believe it or not, I've worked with DC (mainly) and AC electricity for decades (electric forklifts and battery chargers)... but I'm not sure about this one.

I replaced the pickups in my electric guitar with some "hotter" ones than the no-name pickups that came with it. Haven't been able to get it to work right ever since... neck pickup only, then bridge pickup only, now nothing at all.

I'm pretty sure I understand the principles involved, and am more than capable of following the simple wiring diagrams; more likely it's a matter of workmanship than basic knowledge, but in troubleshooting why it isn't working (checking for grounds where there shouldn't be any, etc...), I wound up looking at a parallel circuit: two 500K potentiometers and two pickup coils (wired in series); three resistances in parallel. I'm taking readings at various points, relative to a common ground. The volume pot and the pickup coils are simple: 500K and roughly 13K... but the tone pot confuses me a little. The volume pot resistance is just the resistor track... the wiper isn't involved. The pickup coils are just two coils wired in series... again simple. The tone pot, though presents an problem (to me, anyway.) The reading would be through the pot wiper, and through a portion of the resistor track (depending on the wiper's position in it's travel), then to a capacitor lead, the other cap lead going to the common ground.

I'd *expect* that I'd get no continuity reading at all (infinite ohms, or open) through the cap, provided that the cap is good. Any reading would indicate a shorted cap (it appears to be a poly film; definitely not electrolytic, probably not ceramic), as far as I know.

My basic problem is simply that this thing has me so rattled at this point that I'm starting to question my understanding of the basics; it really *ought* to be working, but it isn't. In all cases, I've been sure if what I've been doing and why I was doing it, and when it repeatedly didn't work, well, confidence rarely thrives on failure. So I'm putting the question out here: should I or should I not be able to read continuity through a (presumed good) cap to ground? Or some "partial" reading, like reading through a resistor? Told'ja it was basic!

Thanks for reading this, and for any clarification (read: hand-holding) you might toss my way!
 

dl324

Joined Mar 30, 2015
9,321
Welcome to AAC!

A capacitor should read open for DC.

Post a schematic showing where you're taking measurements and what is confusing to you.
 

Wolframore

Joined Jan 21, 2019
1,472
Take that cap out and see if it gives you signal. If it works (minus tone control) then cap is bad, replace it. Otherwise, you may have some other issues.
 

atferrari

Joined Jan 6, 2004
3,571
In a certain moment, if the DMM is charging the cap while being measured, that could be construed as measuring continuity.
 

AlbertHall

Joined Jun 4, 2014
8,754
If you do not disconnect the capacitor from the circuit then you should measure a resistance through the tone controls and pickup coils. The value read will depend on the tone control settings.
 

Thread Starter

kharrisma

Joined Dec 9, 2019
3
Hey Folks, here's a schematic for the circuit I'm working on:IMG_20191210_0001.jpgI'm placing the negative prod on the common ground, and the positive prod where each pickup output wire (red) connects to the volume pot. As it stands now, I'm getting continuity pretty much everywhere I put the prod (which obviously isn't right...) I'm curious to know what ohm reading I *should* be getting, given this schematic and the values listed.
 

AlbertHall

Joined Jun 4, 2014
8,754
Assuming nothing connected to the jack, the selector switch set to either of the coils, you should measure the resistance of the two coils in series (13k) in parallel with the volume control (500k) which is about 12.7k.
 

Thread Starter

kharrisma

Joined Dec 9, 2019
3
Thanks for the input... I was pretty sure I could discount the tone pot / cap part of the circuit due to the presence of the cap (since a cap acts as a DC uncoupler, passing only AC, which I *knew*, but sometimes you get 'battle-rattle', and need a little support. Thanks for offering that!
 
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