help with energy concepts 30820 oscilloscope

Thread Starter

neospam

Joined Jan 13, 2020
94
learning how this site works too ugg... I dont have the manual for the scope or FG.. no manual or probes.. looking for the ECI 40600 FG manual and/or service manual.
 
"adjusting the probe" or probe compensation "squares" up the corners on a square wave. Theoretically, a square wave requires infinite bandwidth to display.

AUTO-trigger generally gets you to "see" a trace. If there is no trigger signal in the displayed max time, the scope triggers the horizontal sweep.

Note that there is INVERT for channel 2. You can make psuedo-differential measurements by using two proges and ground and ADD + Invert Channel 2. that gives you A-B. It's really (A+GND)-(B-GND)

A General warning. The scope is connected to ground. bad things can happen if the scope's gnd probe goes to a potential above ground and your device is not isolated.

Another warning: Switching power supplies require extreme care when troubleshooting the primary side. It's common is 1.2 Volts above GND.
 

Thread Starter

neospam

Joined Jan 13, 2020
94
"adjusting the probe" or probe compensation "squares" up the corners on a square wave. Theoretically, a square wave requires infinite bandwidth to display.

AUTO-trigger generally gets you to "see" a trace. If there is no trigger signal in the displayed max time, the scope triggers the horizontal sweep.

Note that there is INVERT for channel 2. You can make psuedo-differential measurements by using two proges and ground and ADD + Invert Channel 2. that gives you A-B. It's really (A+GND)-(B-GND)

A General warning. The scope is connected to ground. bad things can happen if the scope's gnd probe goes to a potential above ground and your device is not isolated.

Another warning: Switching power supplies require extreme care when troubleshooting the primary side. It's common is 1.2 Volts above GND.
thanks very much for the information. I been getting back into elc slowly, been watching many videos and reading. Actually just trying to learn elc. diagnostics better and to use my brain more :) very much appreciate any information.

would have never guess the circuit to be 1.2v on the primary side, would have guessed more around 5v. interesting
 

Thread Starter

neospam

Joined Jan 13, 2020
94
Given the square wave and sawtooth look OK I think the strange 'sine wave' is much more likely to be the generator than the scope.
Does CH2 look the same? If it does your scope is looking pretty healthy.
The strange image in the big picture is because the volts/div is set much too low and the time/div is also set very low.

Now try connecting the generator via the probe. Start with X1 and you should get the same on the scope as with the BNC cable.
If that looks OK, set the probe to X10, set the volts/div three clicks clockwise and you should get the same image again though it may have undershoot or overshoot. To fix that adjust the trimmer on the probe.
update - I just stuck my probe tip into ch1 from the function generator and select sq wave. 1 pict is 1x, the other 10x. I could not get any adjustment from the probes? Wrong capacitance? The screw felt like it would turn and turn? Should it only turn partial turn or 1 turn and stop? not sure I am doing it right.
 

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AlbertHall

Joined Jun 4, 2014
9,326
You nedd the probe the other way round for the adjustment. BNC end to scope, probe tip to generator.
The adjuster does go round and round but only varies over about 180° and then repeats for each revolution.
 

Thread Starter

neospam

Joined Jan 13, 2020
94
You nedd the probe the other way round for the adjustment. BNC end to scope, probe tip to generator.
The adjuster does go round and round but only varies over about 180° and then repeats for each revolution.
that helped, the probs do adjust in 1x and 10x. The left part of the square wave is slightly curved is that normal? All the adjustments on the FG seem to effect the square wave signal, did best to adjust w/o it interfering with the shape of the square. Then adjusted the probe.

I am very green with using a scope. let me know if you think most of the functions work? Or should I test more? I wish to go through the calibration section and check it. not sure how involved that is and if I have all the tools. The cal out does not seem to work, does cal with function generator work correctly like you should me?

When you are board, can you give me a couple simple projects to do to learn how to use it? I been hesitant to hook it to any electrical source until I have a better idea if it works and how to do it. Do you need special probes for low voltage or you just use like what I have?
 

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AlbertHall

Joined Jun 4, 2014
9,326
It is only a 20MHz 'scope so that little final curve on the square wave is to be expected.
Next try different amplitudes and frequencies from the generator and get used to getting them to display on the 'scope.
You might also see the effect of DC coupling the 'scope input on the square wave.
Try very low frequencies with AC coupling and see the effect of that.
 

Thread Starter

neospam

Joined Jan 13, 2020
94
It is only a 20MHz 'scope so that little final curve on the square wave is to be expected.
Next try different amplitudes and frequencies from the generator and get used to getting them to display on the 'scope.
You might also see the effect of DC coupling the 'scope input on the square wave.
Try very low frequencies with AC coupling and see the effect of that.
Let me make sure I understand the terms right. So take a low voltage circuit, turned on or off? Send a square wave via FG into circuit to view? Want to make sure I understand right.

CRT -
amplitude-

On the scope. i.e. 1x probe and 0.1 volt/Div, that is 1/10 of a volt right? In 10x, 1 v reads 0.1 ?

time-

Same for time? 0.1 is 1/10 of a msec? In 10x 1 msec is 0.1 ?

1 div = 1 full line division? 10x = 1/10 of the reading?

The small line = 20th of a division - one little line?
 

AlbertHall

Joined Jun 4, 2014
9,326
The screen is divided into 10 horizontal and 8 vertical divisions.
If it is set to 0.1V/div then if you apply the 0.3V calibrator (assuming you get it working) the signal will occupy 3 vertical divisions. If you feed that signal using 10X probe you will get 0.3 divisions vertically. So you read the 10X as applying to whatever voltage you read from the 'scope screen.
For now forget the 'low voltage circuit' and get used to the range of signals you can get from the generator. You might get someone else to set the generator controls and then see if you can find it on the 'scope. This much like what happens when you go fault finding with the 'scope.
 

Thread Starter

neospam

Joined Jan 13, 2020
94
The screen is divided into 10 horizontal and 8 vertical divisions.
If it is set to 0.1V/div then if you apply the 0.3V calibrator (assuming you get it working) the signal will occupy 3 vertical divisions. If you feed that signal using 10X probe you will get 0.3 divisions vertically. So you read the 10X as applying to whatever voltage you read from the 'scope screen.
For now forget the 'low voltage circuit' and get used to the range of signals you can get from the generator. You might get someone else to set the generator controls and then see if you can find it on the 'scope. This much like what happens when you go fault finding with the 'scope.
thanks for your help. Understand the scale now. Have to see if I can find a manual on it. I thought I did download user manual, but could not find the service. Don't see it on my computer, must have not found one.

Can I inject a sig from the FG into a crossover and view how it handles the crossover points and noise in the components? I just happen to be restoring a set of loudspeakers and have the crossover(s) removed.

well, thanks for everyones help. off to watch the 49s packers game..
 
Compensation is only for 10x or greater probes. Metal screwdrivers can change the capacitance. There are plastic "alignment tools".

In a lot of switching power supplies are either full (120V) or 1/2 wave rectified (240 V) to start wit 3xx volts DC.
The two diode drops at the full-wave bridge cause major issues when trouble-shooting.
 
CAL OUT has a little hole in it. That is for the oscilloscope probe clip. You don't need the ground wire.

other notes:
CH2 red knob is in CAL (or where it's supposed to be)
CH1 red knob is in UNCAL or variable mode within the range.
 
You have the horizontal in x3 in time mode as well. Push the red control in.

You asked for project questions, but lets get operation down first. See if you can read freqency from the scope.

Then set your signal generator for 60 Hz, 1 V p-p. Now try to read AC on your DVM. You should read 0.707 VAC.
 
Can I inject a sig from the FG into a crossover and view how it handles the crossover points and noise in the components? I just happen to be restoring a set of loudspeakers and have the crossover(s) removed.
The speakers probably need to be connected because of the inductance and the load.

Your signal generator probably can't drive the speakers, so you would need an audio amplifier. You MIGHT want to characterize that first. I doubt a load (resistor or speaker) matters. here https://en.wikipedia.org/wiki/Line_level is a blurb about audio levels.

Remember, with a 1 pole filter or just R and C, the -3db point is when the signal decreases by 70.7% or sqrt(2) /2. When they quote frequency response or bandwidth of an amplifier, they use the -3db point.

that fc = 1/(2*PI*R*C) where fc = corner frequency.
 

Thread Starter

neospam

Joined Jan 13, 2020
94
CAL OUT has a little hole in it. That is for the oscilloscope probe clip. You don't need the ground wire.

other notes:
CH2 red knob is in CAL (or where it's supposed to be)
CH1 red knob is in UNCAL or variable mode within the range.
Cal out does not work, appears the circuit is not providing a signal, not sure why yet. When I hooked probe w/o ground I get a bunch of ghosting as in the pict from FG, not sure what it is called. When I hook the ground it clears up.

p.s. I will try with your recommendations and get back.
 

Thread Starter

neospam

Joined Jan 13, 2020
94
You have the horizontal in x3 in time mode as well. Push the red control in.

You asked for project questions, but lets get operation down first. See if you can read freqency from the scope.

Then set your signal generator for 60 Hz, 1 V p-p. Now try to read AC on your DVM. You should read 0.707 VAC.
I only have a function generator?

thanks will try..
 

Thread Starter

neospam

Joined Jan 13, 2020
94
The speakers probably need to be connected because of the inductance and the load.

Your signal generator probably can't drive the speakers, so you would need an audio amplifier. You MIGHT want to characterize that first. I doubt a load (resistor or speaker) matters. here https://en.wikipedia.org/wiki/Line_level is a blurb about audio levels.

Remember, with a 1 pole filter or just R and C, the -3db point is when the signal decreases by 70.7% or sqrt(2) /2. When they quote frequency response or bandwidth of an amplifier, they use the -3db point.

that fc = 1/(2*PI*R*C) where fc = corner frequency.
The crossover is completely removed from cabinet. It is sitting on the bench, one torn apart and drawing a schematic of it. I am in the possess of reconing the woofers and testing the other 6 horns, and rebuilding the crossovers. One crossover has a bad inductor, and will rebuild them both.

wondering if I could send a signal into the crossover from the FG and what I might learn from it. Can I see anything with the crossovers, filters, dirty pot, breaker, etc. Just thought it would be interesting to view the signal cut off freq if possible.
 
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