Scopes and Pedal Building

[skypn]

Figured I would start here. I was recently given an old Tektronix 453 scope. I know very little about scopes. I have found some basic info on how to use them in general. Where can I find info on how to use them in pedal building specificity?
Side bar: the first thing I am going to try and do is to id an unknown inductor using an LC circuit and function generator.
TIA

[mauman]

Here's how I use a scope when building pedals.  I think your 453 is a dual-trace, which is handy for circuit testing.  I mostly use 2 traces, one at the input of the circuit to set the function generator level and frequency, and one at the circuit output or as a signal tracer at various points in the circuit.  If your scope has a ~1 meg input impedance, you can use it to terminate the output jack of a pedal.  If you need to hear the output as well, you can bridge the output to the scope and to an amp.  These are all pretty basic functions, in order of frequency of use:
1. Verify that what I modeled in LTSpice works out about the same in a real circuit.
2. Test completed builds for frequency response, levels, waveforms, and noise.  I usually keep a spreadsheet on each pedal's profile so I can compare it to expectations, and to similar builds.
3. Troubleshoot (signal tracing), I identified an oscillating op amp the other day like this.
4. Today I tested a DC/DC converter for radiated noise to see how far it needs to be from low level signals to avoid interference.
5. Occasionally measure LFO operation and calibrate chorus pedals.
There's lots more that I'm not smart enough to figure out! You can Google "oscilloscope basics" and get a ton of YouTube videos and PDF guides, including a Tek 453 manual.   

[skypn]

First and foremost, thank you for your reply. Of course I have many questions, but am only asking one.

2. Test completed builds for frequency response, levels, waveforms, and noise.  I usually keep a spreadsheet on each pedal's profile so I can compare it to expectations, and to similar builds.

There I'm lost. I assume levels means , like after a trans, when the signal should be louder, see that it is, what shape the waveform is (ie. sine tri or sq) any noise will look like ugly wave forms. As far as Freq response, I wouldn't have a clue . Are we looking for build mistakes here, or maybe differences from one component and another of the same marked value that was in my parts drawer?

There's lots more that I'm not smart enough to figure out! You can Google "oscilloscope basics" and get a ton of YouTube videos and PDF guides, including a Tek 453 manual.   

I have a manual, and some basic guides.

[mauman]

I assume levels means , like after a trans, when the signal should be louder, see that it is, what shape the waveform is (ie. sine tri or sq) any noise will look like ugly wave forms.

Right.  A good way to start is take a true-bypass pedal that you like, put a sine wave signal in*, tie one scope channel to the input and one to the output.  Look at the signal with the pedal bypassed, and adjust the vertical and horizontal to see the same waveform and levels on both channels.  Now turn on the pedal, adjust the output channel vertical to show the whole waveform, and see what effect each of the knobs has.  You can see level changes with volume and gain knobs, different clipped and distorted waveforms (rounded, cut-off tops, peaked, etc.).  Tone knobs will give you level changes (vertical shifts) as well as phase changes (horizontal shifts).

As far as Freq response, I wouldn't have a clue .

This is just how the pedal bumps various frequencies up or down.  A buffer has a flat response, whatever you put in comes out the other end with just the level changed. Some boosts as well, such as the SHO.  Most other pedals boost or cut various frequencies differently, usually cutting bass and treble.  You can put a signal in at different frequencies, say 80 Hz, 800 Hz, and 8000 Hz, and measure the level coming out.  You'll probably see lower levels at 80 and 8000.  The difference is the frequency response.

Are we looking for build mistakes here, or maybe differences from one component and another of the same marked value that was in my parts drawer?

Mistakes definitely, but even identical pedals will be different due to the accumulation of small differences in the components.  Pots, for example, can be +/- 20%, so a 100k Gain pot could be 80k to 120k.  Most caps also have a 20% tolerance which can alter the frequency response and tone controls.  But it's also helpful in understanding how a Fuzz Face and a Tubescreamer are similar and different. You can visualize "clipping" and other interesting things.

* All you need is a steady clean signal of one frequency, doesn't have to be calibrated.  If you need something like that, you can build your own, check out http://www.valvewizard.co.uk/siggen.html