So I have been building pedals for over ten years and really enjoy it. I love modulation effects and delays and I know I can take it to the next level if I learn how to use an oscilloscope. I do have one I have just never really messed with it. It is older but it was given to me and it works, lol. There are a few pedals i have where I have reached a point I want to put a little effort in to make them that much better instead of doing it by ear (works pretty good most of the time). Examples are the Blueshift and DMM from madbean. Most of the tutorials online I have found talk about stuff I will never use or likely need to know how to do. I just want something that shows me how to do things that are useful for pedals. I am looking for suggestions or tutorials that you guys have found that helped you with this. Thanks in advance.
Basic Oscilloscope tutorials
- Thread starter Audandash
- Start date
GAStan
Member
The best thing to do is just start using it.
On the scope it should have a test output, a squarewave. Put the probe tip on that and figure out how to adjust the SYNCronize or Trigger (same thing) for a stable waveform. Also learn to adjust AMPLITUDE and TIME/DIVISION. These labels can change from brand to brand. Post a pic of the front of the scope and I can tell you what's what.
On the scope it should have a test output, a squarewave. Put the probe tip on that and figure out how to adjust the SYNCronize or Trigger (same thing) for a stable waveform. Also learn to adjust AMPLITUDE and TIME/DIVISION. These labels can change from brand to brand. Post a pic of the front of the scope and I can tell you what's what.
KreoPensas
Member
Even old sillyscopes are very useful, you learn to interpret. I have one circa 1972 that belonged to a childhood friend's dad. We were forbidden to touch it. Now it lives on my bench.
GAStan
Member
You might also consider either an Audio Signal Generator or a Cable like this with the appropriate phone connection and Tone Generator app. I downloaded "Frequency Sound Generator" by LuxDeLux and it's good so far; very basic and simple to use. I paid for the pro version-you pay what you want, not sure what minimum is i think $1? I paid $3 and well worth it to get rid of ads. Be sure to look at settings as it defaults to Run In Background which i don't like.
GAStan
Member
Tektronix is a great scope.
Once scope is on and CRT has came on press and hold BEAM FIND button that is next to CRT. If necessary adjust various POSITION knobs along top to center trace. Release BEAM FIND.
Start with a single probe plugged into Channel 1. Put the CH1 BOTH CH2 switch to Channel 1. CH2 INVERT to NORMal. ADD ALT CHOP to middle for Alternate. Connect the probe tip to the PROBE ADJUST terminal. If you have a spring loaded hook on the probe that's even better.
In VERTICAL box: Look on the probe it should indicate that it is 1x or 10x or have a switch to select 1x or 10x. If it has a switch put it on 1x. On the CH1 VOLTS/DIV knob set it to 1 on either the 1x or 10x marking depending on the probe. AC GND DC switch to DC. The small center CAL knobs should ALL be turned fully clockwise.
In HORIZONTAL box: X1 ALT MAG switch to X1. Turn SEC/DIV to 10ms, again CAL center knob fully CW. X5 X10 X50 switch doesnt matter, only used if X1 ALT MAG switch in MAG.
In TRIGGER box: SLOPE can be either Rising (up) or Falling (down). Switch in MODE box either P-P AUTO or NORM. HOLDOFF knob to MIN (fully CCW). Left switch in SOURCE box to CH1. Right switch is only used if left switch fully down in EXT. COUPLING switch can be either AC or DC. Use DC for now. Once switches are set and probe connected adjust LEVEL knob until green TRIG'D LED is on. You should have a signal on the screen by now. You can vary CH1 VOLTS/DIV and SEC/DIV knobs to view waveform. If waveform isn't a nice looking squarewave look on the probe, either the handle or part that is plugged into scope, for an adjustment screw. Adjust this until waveform is a good squarewave.
Once scope is on and CRT has came on press and hold BEAM FIND button that is next to CRT. If necessary adjust various POSITION knobs along top to center trace. Release BEAM FIND.
Start with a single probe plugged into Channel 1. Put the CH1 BOTH CH2 switch to Channel 1. CH2 INVERT to NORMal. ADD ALT CHOP to middle for Alternate. Connect the probe tip to the PROBE ADJUST terminal. If you have a spring loaded hook on the probe that's even better.
In VERTICAL box: Look on the probe it should indicate that it is 1x or 10x or have a switch to select 1x or 10x. If it has a switch put it on 1x. On the CH1 VOLTS/DIV knob set it to 1 on either the 1x or 10x marking depending on the probe. AC GND DC switch to DC. The small center CAL knobs should ALL be turned fully clockwise.
In HORIZONTAL box: X1 ALT MAG switch to X1. Turn SEC/DIV to 10ms, again CAL center knob fully CW. X5 X10 X50 switch doesnt matter, only used if X1 ALT MAG switch in MAG.
In TRIGGER box: SLOPE can be either Rising (up) or Falling (down). Switch in MODE box either P-P AUTO or NORM. HOLDOFF knob to MIN (fully CCW). Left switch in SOURCE box to CH1. Right switch is only used if left switch fully down in EXT. COUPLING switch can be either AC or DC. Use DC for now. Once switches are set and probe connected adjust LEVEL knob until green TRIG'D LED is on. You should have a signal on the screen by now. You can vary CH1 VOLTS/DIV and SEC/DIV knobs to view waveform. If waveform isn't a nice looking squarewave look on the probe, either the handle or part that is plugged into scope, for an adjustment screw. Adjust this until waveform is a good squarewave.
KreoPensas
Member
10 mhz service scope made by a subsidiary of Tektronik, Telequipment.
Not to clutter the thread, a different but analogous set of knobs to compare is an extra justification to show off an old friend.
Not to clutter the thread, a different but analogous set of knobs to compare is an extra justification to show off an old friend.
GAStan
Member
Shrt version of how an old CRT oscilloscopes works:
CRT=Cathode Ray Tube. Internally it generates a beam that when it strikes the phosphorus coating inside the screen of the tube lights it up and it will glow for a very short time. This beam creates a pinpoint of light that can be steered to any point on the screen. Typical operation will move the beam from left to right as viewed from the front. You can see it move as the speed is slowed down by turning the SEC/DIV knob CCW. When the beam is sped up by turning the knob CW it begins to move so fast it appears to be a solid line. The SEC/DIV knob is calibrated that each division of the black lines printed on the screen is equal to the setting on the knob. Once the timing of a waveform is known the frequency can be calculated.
Similarly the beam will deflect up/down by voltage as the beam moves left to right creating the waveform seen. The beam is literally drawing the waveform vertically by voltage as it moves horizontally based on time.
The beam requires something to "trigger" it to start. In Auto trigger mode it just automatically starts without an external trigger, thus the waveform may not be consistently drawn in the same location horizontally, it can appear to dance back and forth randomly. In NORMal trigger mode it looks for a trigger from whatever is selected by the SOURCE switch(es), CH1 in the previous post. It is looking for either a Rising or Falling voltage, selected by the SLOPE switch. The LEVEL knob is setting the voltage level the beam sweep is triggered at.
To summarize, the beam draws a waveform left to right, vertically by voltage horizontally by time. The beam needs a trigger to start each sweep.
Hopefully this helps. Feel free to ask any questions and I'll be happy to help or someone else will jump in.
CRT=Cathode Ray Tube. Internally it generates a beam that when it strikes the phosphorus coating inside the screen of the tube lights it up and it will glow for a very short time. This beam creates a pinpoint of light that can be steered to any point on the screen. Typical operation will move the beam from left to right as viewed from the front. You can see it move as the speed is slowed down by turning the SEC/DIV knob CCW. When the beam is sped up by turning the knob CW it begins to move so fast it appears to be a solid line. The SEC/DIV knob is calibrated that each division of the black lines printed on the screen is equal to the setting on the knob. Once the timing of a waveform is known the frequency can be calculated.
Similarly the beam will deflect up/down by voltage as the beam moves left to right creating the waveform seen. The beam is literally drawing the waveform vertically by voltage as it moves horizontally based on time.
The beam requires something to "trigger" it to start. In Auto trigger mode it just automatically starts without an external trigger, thus the waveform may not be consistently drawn in the same location horizontally, it can appear to dance back and forth randomly. In NORMal trigger mode it looks for a trigger from whatever is selected by the SOURCE switch(es), CH1 in the previous post. It is looking for either a Rising or Falling voltage, selected by the SLOPE switch. The LEVEL knob is setting the voltage level the beam sweep is triggered at.
To summarize, the beam draws a waveform left to right, vertically by voltage horizontally by time. The beam needs a trigger to start each sweep.
Hopefully this helps. Feel free to ask any questions and I'll be happy to help or someone else will jump in.
KreoPensas
Member
If you have any contact cleaner, hit what you can get to on ch 1. Might only be crud on the BNC, the ac - gnd - dc slide switch
GAStan
Member
Nice!
If you haven't already try out the brightness and focus knobs. In your picture the trace looks a bit bright.
To work on a pedal you need two connections, a ground reference and the point you wish to look at. Connect the clip on the black wire to a ground point on the pedal and the tip to the point you wish to look at. On the probe just up from the tip is a metal band. Electrically it is the same as the black ground wire. Be careful not to touch it to anything you don't want to ground out. If it didn't come with the plastic cover it's a good idea to cover it with heat shrink. I've worked on high voltage devices and believe me inadvertent contact of that with the wrong point can make for some interesting fireworks.
You've got the basics now, start trying it out on other things like you used the audio probe on. Once you look at a live sound signal i think you'll understand why a simple single tone, which is a steady sine wave on the o'scope, is useful for troubleshooting with an o'scope.
For working on pedals you'll probably want the AC GND DC switch in DC mode. GND puts the trace at a flat zero volts (Ground) level. If looking at something such as input voltage (+9vdc) you would put that switch to GND and set your zero reference by moving the trace down to one of the lines printed on the screen. Put the VOLTS/DIV on 2 volts. Now put the switch from GND to DC and put the probe tip on the input power. The trace will jump up but remain a flat line. Count the solid lines from the zero reference you set to its current position. Each line is 2 volts. On the center vertical line are tic marks dividing each line by 5, so on a 2 VOLTS/DIVision setting each tic mark is .4 vdc. (2/5=.4). Just count the lines and if the trace is between the lines use the tic marks to measure the voltage level. You can use this same method (with a different VOLTS/DIV setting) to measure the voltage level of the square wave in your picture.
Edit: spelling & grammar
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