# Hello, my name is bifurcation and I don't know how to use a multimeter



## bifurcation (Jul 13, 2019)

So _*ahem* *cough*_ as I've tried to build pedals _(and inevitably screw up 3/4s of them,)_ I've gotten great troubleshooting tips from y'all... but often still can't figure out what's going on with my circuit.

Folks suggested a multimeter and oscilloscope would be useful, so I picked those up and.... 





... I can't figure out what to do with them. 

I've looked for tutorials and/or videos, but haven't found anything super useful. I even found one called "how to troubleshoot with a multimeter," but I still don't really get what I'm doing wrong.

Like, even just setting the multimeter on the speaker icon, I touch the two probes together and get a beep, but literally don't get a beep if I touch the two ends of a resistor. I thought... but... ???

Anyway, this is an overly long way of asking how people learned their tools and if anyone has suggestions (or links to tutorials or videos) on how to ... multimet.

... and don't get me started on the oscilloscope, I haven't even turned this on. ?


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## Robert (Jul 13, 2019)

The "speaker icon" is a continuity test.    You use that function to check for a solid connection (low resistance) between two points.    Aside from voltage measurements, this is _probably_ the function you'll use most when troubleshooting.

A resistor resists the flow of current, so unless it's a really low ohm resistor (less than 50 - 100 ohms) it won't give you a beep because it's not a path of low resistance.

If you've ever wondered if a trace was damaged, or a wire was broken, or a switch was good... that's the mode you would use to find out.

Random scenario:
Imagine you have a true-bypass pedal sitting in front of you and power isn't applied to the circuit, but (for some reason) you want to know if the footswitch is On or Off.... How can you tell without applying power?

Switch your meter to the continuity test and put one lead on the Tip connection of the Input jack, and the other lead on the Tip connection of the Output jack.  If it makes a solid beep, the pedal is bypassed. (The 3PDT footswitch is connecting the jacks together).

If it doesn't make a solid beep, the footswitch is switched On.


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## bifurcation (Jul 13, 2019)

Nice, thanks!

One video seemed to suggest you could use the continuity test to see how far signal gets through the entire circuit, which seems impossible.


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## sertanksalot (Jul 17, 2019)

First rule to remember with a multimeter is... if you are measuring current (amperes), do so *IN SERIES* with your working circuit, especially if you are using an analog meter.  E.g., the guitar pedal circuit is drawing 5mA.  It is possible that your multimeter has protections against over current, but it is best practice not to blow a fuse.

Voltage can be done for any reference point and/or in parallel.  E.g., the 9V battery is showing 8.7 volts.

I hope this helps.

P.S.  Like with a tablesaw, if you have the same number of fingers when you finish using it, then you used it right.


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## zgrav (Jul 17, 2019)

"One video seemed to suggest you could use the continuity test to see how far signal gets through the entire circuit, which seems impossible."

What you have to do is match the parts on your pcb to what you see in the circuit diagram.   The line in the circuit diagram shows you what parts are connected to each other.  Use the continuity test to see if the parts are connected the way they should be --- check if the tip of the input jack for the "IN" side connects to the footswitch.   Then see if the lug from the footswitch that is supposed to connect to "IN" on the PCB actually has continuity.  Then see if the spot where the "IN" wire connects to the PCB connects to the first part shown on the circuit diagram.  You gradually work your way through all of the connections to find out ".. how far the signal gets through the entire circuit...."


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## zgrav (Jul 17, 2019)

you probably won't use your oscilloscope for a while to troubleshoot your PCBs.  Most of the things you end up checking for are bad solder connections, broken traces, things that accidentally connect when they should not, and whether the parts are the right value and --for some capacitors -- whether they were installed with the + and - sides in the right places.


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## bifurcation (Jul 17, 2019)

zgrav said:


> "One video seemed to suggest you could use the continuity test to see how far signal gets through the entire circuit, which seems impossible."
> 
> What you have to do is match the parts on your pcb to what you see in the circuit diagram.   The line in the circuit diagram shows you what parts are connected to each other.  Use the continuity test to see if the parts are connected the way they should be --- check if the tip of the input jack for the "IN" side connects to the footswitch.   Then see if the lug from the footswitch that is supposed to connect to "IN" on the PCB actually has continuity.  Then see if the spot where the "IN" wire connects to the PCB connects to the first part shown on the circuit diagram.  You gradually work your way through all of the connections to find out ".. how far the signal gets through the entire circuit...."



Awesome, thanks!


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## Jbanks (Jul 20, 2019)

Also an audio probe is super helpful for testing the signal path for trouble shooting pedal problems.  There are plenty of guides by googling “audio probe”. 

Here’s one I used to make my probe. Really really simple, but super useful tool. 



			Simple Circuit Debugging


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## bifurcation (Jul 20, 2019)

Jbanks said:


> Also an audio probe is super helpful for testing the signal path for trouble shooting pedal problems.  There are plenty of guides by googling “audio probe”.
> 
> Here’s one I used to make my probe. Really really simple, but super useful tool.
> 
> ...


 Awesome, thanks!


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