oscilloscope newbie

[milo_ec]

Hi, I am triying to get some equipment for my mini lab to test a tube preamp and those second hand analog oscilloscopes are abaut 500$ in my country, even those dso nano are at least 200$... my oscilloscope is actually a nail conected to a 0,2uFcapacitor and a  50kOhms potentiometer, and pluged to the mic in of my computer  .... is the dso203 (http://youtu.be/SOdGPUGi9wQ) worth it in that case as an improvement to my nail??  ....? It is only for audio aplications for now, but it is very dificult to trace signal without a voltage reading.... and I fried one of the audio chanels of my computer, so I need something that can work, and dose not damage my computer (that I realy need at my job)...

My salary is 350$ and I have saved 240$ for these, that is about what I am going to have to pay for that oscilloscope with shiping and hopefully I wont have to pay taxes for it, in order to be tax free, it has to be less than 4 kilograms or 400$...

btw, sorry for my bad english, my native language is spanish... 

[Simon]

Try getting the cheapest stand alone oscilloscope. You will find a 50MHz is much cheaper than the new faster ones so might be better bang for buck for you.

[tautech]

as an improvement to my nail??

Nearly anything will be an improvement on your nail. 
Personal safety first.
Probe effect on the DUT second.
Ability to take accurate frequency and voltage measurements.

And protection of your computer.

Many of the entry level DSO's will suit your requirements, my preference is for those with 400V capable BNC inputs.

[milo_ec]

www.politicallyincorrect.eu - saying it how it is !

lol tha page is forbidden were I live  , it gives me a 403 error, I will try to acces it with a cuple tricks I have... and thaks for the advice!... 

[Simon]

www.politicallyincorrect.eu - saying it how it is !

lol tha page is forbidden were I live  , it gives me a 403 error, I will try to acces it with a cuple tricks I have... and thaks for the advice!... 

same error here, I need to sort out the redirect page link, try: http://politicallyincorrect.eu/wiki/index.php I', currently rebuilding it as a wiki instead of as a wordpress website

[IconicPCB]

Milo,

Where are You?

[milo_ec]

Milo,

Where are You?

Ecuador, Its the most beautiful country, but politicians are the reincarnation of the devil... after some times you find the cracs in the sistem and learn how to live with it, like geting a nail to work as a very improvise oscilloscope lol...

[vk6zgo]

An Oscilloscope makes fault finding a lot easier,but back in the tube days,they were very costly,& most repairs of Audio equipment were done using a Multimeter.

If you have a schematic diagram & a DMM,you should be able to check around the circuit for the correct operating voltages.

A DMM has an advantage over the old Analog multimeters,in that they will read ac voltages up into the Audio frequency spectrum,so you may be able to signal trace,too,depending on the signal levels.

You can easily kill a Soundcard probing around tube circuits using your method---I would cease using it.

[milo_ec]

You can easily kill a Soundcard probing around tube circuits using your method---I would cease using it.

well it was a cheap 50$ souncard, and it actuly was a little acsident, I was looking for noice at the output of the rectifying tube, and I touch the 110v ac main power input, so im just woried that it can zap the pci lanes, in that case it can damage the videocard, and that is a lot more imprtant for me because I work as a graphic designer.

But thaks!!.... very usefull advice, and actualy first I was looking for a solution like that becouse i do test the voltage before i probe, but i have now an amplified signal, but it is distorted, and i am dealing with that now...

I have vary the voltage at both the grid and the cathode, and play a little with the load resistace and the output capacitor, and it is geting better, but the volume goes too low, it is abot double the voltage of the computer max output (with a 440hz sin wave)....

[RedOctobyr]

I have heard of people using external, USB soundcards, for use as soundcard-oscilloscopes.

There is apparently less risk of damaging the rest of your computer, if you connect a signal whose voltage is too high (but this may mean too high like 3V instead of 1V, not 110V). At a minimum, hopefully you'd just damage an easily-replaced external item, not something in your laptop/desktop, with increased risk of motherboard damage.

Just something to consider if you keep using a soundcard.