My first Oscilloscope!

[Menticol]

Hello guys!! It has been a very long time without seeing your names on the screen, I hope all of you are doing great.

A thing that I strongly refuse to do is killing my electronics passion, even if I'm not specially good at the field. And for that I should thank a group of electronics engineers that work with me. A couple of weeks ago they laughed of my hobby with phrases like "You are an Industrial Designer. Why do you like to learn electronics? better go to make some... I don't know, pretty drawings, art...".

Well, they can go to hell now, because I finally reached my dream of getting an oscilloscope!! hahaa!! No more souncard-parallel port-modified TV crap.



Well, maybe you can't understand my joy because getting a second hand oscilloscope on the U.S.A or U.K. is easier than buying bread and milk. I'm also very aware that a DSO oscilloscope gives more options (even for some audio and not very high frequency beginner applications like mine).

But remember that were I live is hard to find this things outside very specialized circles, and importing them is much more expensive than the instrument itself. My options were

* UT-81B toy - $350K COP
* This $200 COP unit
* A 20 Mhz 2 channel LG Analog oscilloscope - $600K COP
* DSO oscilloscope of doubtful manufacturer - $1,5M COP (somewhat like 1500 USD adjusting for the cost of living)

 

[Menticol]

Time for Testing!

Well, the 60 Hz AC mains signal (feed via a small 110v-9v transformer) looks somewhat chopped, I don't know if you agree.



The 1 khz calibration signal sometimes looks good compared with the picture depicted in the manual, but other times looks severely distorted.



I hope this improves using new probes. The OEM probes had been very abused, one is missing the circuitry after the BNC connector. Another theory is bad electrolytic capacitors, let's see what Google has to say about this

 

[JimB]

Nice basic scope, I should work well for you.

Well, the 60 Hz AC mains signal (feed via a small 110v-9v transformer) looks somewhat chopped, I don't know if you agree.

The AC mains is often far from a nice sine wave!

The 1 khz calibration signal sometimes looks good compared with the picture depicted in the manual, but other times looks severely distorted.

The distorted one just looks like it is over compensated, too much high frequency response.

I hope this improves using new probes. The OEM probes had been very abused, one is missing the circuitry after the BNC connector. Another theory is bad electrolytic capacitors, let's see what Google has to say about this

Oscilloscope probes are usually abused in the workplace, the tips get lost, people have no idea what the compensation is for, etc etc.
Bad electrolytics? I don't think so!
Electrolytic capacitors have become the whipping boy of modern electronics.

JimB

 

[tvtech]

Bad electrolytics? I don't think so!
Electrolytic capacitors have become the whipping boy of modern electronics.

JimB

Hi Jim

I agree. Sure Electrolytic's fail.....but are not a cure all solution to faults

Always difficult if people don't know what they are doing or rather UNDERSTAND what they are doing.....and why....
I will leave it there.

Regards,
tvtech

 

[atferrari]

Good start, Menticol.

I spent almost 30 years using my first scope (10 MHz) until my financial situation allowed, some 2 years ago jumping up to a 100 MHz DSO. Here we are in the same if not WORST situation than you for anything that is buying from abroad.

Ya que estamos, congratulaciones por tu selección. Pusieron mucho huevo y merecen respeto.

 

[KeepItSimpleStupid]

probe compensation

A square wave will only look square with a x(##), e.g. x10, x100 etc probe. There will be an adjustable capacitor on the probe or connector that is varied until the calibrate wave is square. This compensates the probes capacitance.

 

[fezder]

now that you got your skope, play around with it . the fact you measured mains via isolation transformers tells that you at least measure safely! don't get me wrong, i ddidn't think you'd do silly stuff . i did myself back couple days ago silly stunt, but one good step in learning is forgiving mistakes: nothing that horrible, i just shorted my mesurement diode/s (cant recall well...) when i accidentaly used two ground clips, silly i know!

 

[Menticol]

Hello TVtech!

Following my history of posts about electronic projects that refuse to work or explode, I see why you suspect that I have no idea of what I'm doing. Usually its the case, but not this time.

I tried using the compensation circuitry included on the probe to make the test wave look like the manual's photo, but it seems to be inoperative.

Now, about the electrolytics, I know capacitor faults would be more associated to situations were the oscilloscope totally refuses to turn on (i.e. the HV section is dead). But I tough that checking the capacitors may be a good idea...

first because the oscilloscope's manual empathizes on the necessity of high quality mains for feeding the unit, to avoid funky readings or blowing up the whole thing. Maybe the manufacturer knew that their mains filtering was not very good?

And second, after spending some nights reading this vintage electronics site (by the way very good one) most of the problems the author finds are related to old electrolytics.

I totally agree with you on the fact that changing capacitors on the dark is not definitely not a good idea.

Hi Jim

I agree. Sure Electrolytic's fail.....but are not a cure all solution to faults

Always difficult if people don't know what they are doing or rather UNDERSTAND what they are doing.....and why....
I will leave it there.

Regards,
tvtech

 

[Menticol]

Hola Atferrari!

I'm very happy to see again a Latin American friend on this grounds. Indeed, is very hard to get electronics test equipment, and more in your case because of your work with micro controllers requires higher specs. I ever wondered if there was any chance of building or at least assembling some of the tools locally, it would be a good business opportunity.

Thank you by your cheers to the Colombian soccer team!! the guys were a real surprise, given our performance on the previous world cups. As the saying goes, a new broom will always clean better, and this guys are totally a new generation.
A little off-topic to end the post: The referee had made some strange decisions during the match but it's no surprise: with all the millions of euro involved and the delicate social situation the locals simply cannot afford to lose. I have hope in the other teams to prove me wrong!

Good start, Menticol.

I spent almost 30 years using my first scope (10 MHz) until my financial situation allowed, some 2 years ago jumping up to a 100 MHz DSO. Here we are in the same if not WORST situation than you for anything that is buying from abroad.

Ya que estamos, congratulaciones por tu selección. Pusieron mucho huevo y merecen respeto.

Thank you for the tip KISS, I didn't know that. I'll experiment with the other probe to see if the attenuator installed on that one works.

probe compensation

A square wave will only look square with a x(##), e.g. x10, x100 etc probe. There will be an adjustable capacitor on the probe or connector that is varied until the calibrate wave is square. This compensates the probes capacitance.

No fezder, just the opposite: your comment is very opportune. For example I've read lots of people that blew their scopes because their served as a path to earth... now I understand the necessity of a decent 1:1 isolation transformer! Luckily this oscilloscope have no third-prong to earth, so it's one reason less to worry.

now that you got your skope, play around with it . the fact you measured mains via isolation transformers tells that you at least measure safely! don't get me wrong, i ddidn't think you'd do silly stuff . i did myself back couple days ago silly stunt, but one good step in learning is forgiving mistakes: nothing that horrible, i just shorted my mesurement diode/s (cant recall well...) when i accidentaly used two ground clips, silly i know!

 

[killivolt]

killi, says nice scope; at work I have a very old Tektronix. At least your learning the "how" to use one; and like me some can do or absolutely don't do.

Good luck.

kv

 

[tvtech]

Hello TVtech!

Following my history of posts about electronic projects that refuse to work or explode, I see why you suspect that I have no idea of what I'm doing. Usually its the case, but not this time.

I tried using the compensation circuitry included on the probe to make the test wave look like the manual's photo, but it seems to be inoperative. I hope to replace the probes as soon as I get some money.

Now, I know that electrolytic capacitor faults would be more associated to situations were the oscilloscope totally refuses to turn on (i.e. the HV section is dead). But I tough that checking the capacitors is not a totally bad idea for two reasons:

First, this oscilloscope's manual empathizes on the necessity of high quality mains for feeding the unit, to avoid funky readings or blowing up the whole thing. Maybe the manufacturer knew that their mains filtering was not very good?

And second, after spending some nights reading this vintage electronics site (by the way very good one) most of the problems the author finds are related to old electrolytics.

Start changing capacitors on the dark? definitely not a good idea. But at least a good reason to build the ESR meter project, don't you think?

Hi Menticol

Sorry if I offended you.

All I was trying to do was wean Newbies from blaming all faults on Electrolytics....sure they do fail....
The first thing a Newbie does these day's with anything TV related.....is change Electrolytics....
And they are not always to blame....many times a fault lies elsewhere.
That's where the understanding part comes in.

That's all

Regards,
tvtech

 

[Menticol]

Oh no problem Tvtech, absolutely no offence taken!
By the way, are you still working with the "monkey-see, monkey do" guy? That story gave me a good laugh

I've been experimenting with the oscilloscope last night. After replacing the GND cable and the alligator clip from the less damaged probe the improvement was huge!

60 Hz mains



A cheap 12Vdc -110 Vac inverter. At first it looked like glitter.



But after connecting some resistive load in parallel with the oscilloscope the graph acquired more meaning. I still don't understand why the trace disappears at some points of the wave, I wonder if its a consequence of the "modified sine wave" technique.



A 1v to 3v Joule thief


The last one was funny: I hooked a small dc motor to a dremel, trying to imitate a Motor-generator set. Perfect sine wave? maybe in my dreams

 

[JimB]

I still don't understand why the trace disappears at some points of the wave,

The rate of change is too fast for the scope to display.
If you turn up the brightness, and/or speed up the time base, you may see the fast changes.

JimB

 

[tvtech]

Oh no problem Tvtech, absolutely no offence taken!
By the way, are you still working with the "monkey-see, monkey do" guy? That story gave me a good laugh
QUOTE]


Hi Menticol

He is History....kinda outfoxed himself...beating people up....and fired.

What a Monkey . Busted for being useless...and then tries to defend it...

Only in Africa

Regards,
tvtech

 

[killivolt]

Oh, ya. ........................"No comment"

 

[throbscottle]

Congratulations Menticol, I can see you are a proud "daddy" to this instrument! I was so lucky to get my Cossor for 99p last year as faulty - not much wrong, easy fix