Help-Looking for Oscilloscope in Toronto

[gregas]

Hey guys
I recently built a D. I.Y. tube amp kit.
I'm not very satisfied with the sound of it at higher
Volume. Sounds harsh to me with some
Distortion. I'd like to diagnose it. Does anyone
Have an oscilloscope they're not using?
Something with 2 channels that will do 20 MHz?

 

[Dilbert]

Toronto Surplus used to have a very nice selection. I bought my Tek 465 from him. Not the lowest prices, however. But I did get a scope in good condition and it has been working flawlessly for many years.

Home page

 

[gregas]

This is my first build. So just getting into
The hobby. I'm hoping to get a hold of an oscilloscope for not too much money. Perhaps someone has one collecting dust in a basement.

 

[DUG]

How about one of these for $125

Two x10 probes included (not the ones in pix)

If interested I can take more pictures.

 

[dangus]

Ham radio swap meets usually have some cheap scopes. But don't overlook the power of a computer sound card, running something like RMAA.

 

[gregas]

Ham radio swap meets usually have some cheap scopes. But don't overlook the power of a computer sound card, running something like RMAA.

Would I need to make a probe for this? How would it work?

 

[VictoriaGuy]

But don't overlook the power of a computer sound card, running something like RMAA.

I'd recommend a 'throwaway' computer for that, unless you have a good interface to protect the computer.
I 'blowed up' a soundcard once, using the computer as a signal source for a chipamp that wasn't properly wired.
Fortunately it was an old tower 'puter and only the soundcard went.
I wouldn't try the same thing with a decent laptop or newer motherboard with integrated audio.
Anyway, a real scope is more fun, even if less 'powerful' than some of the computer software. I like lots of real controls to adjust!

The hamfest recommendation is a good one, though it can try one's patience to wait for the annual event if you want something NOW! It's probably more efficient to get in touch with somebody who goes to hamfests and can't resist the 'just one more' (scope, function generator, box of tubes, etc.) syndrome...and has too much gear in the basement....not naming names...

 

[Dilbert]

Gregas, check your PM’s.

 

[VictoriaGuy]

About soundcard scopes :
I've never used one, but in post #625 of the Boyuu A9 thread:
Boyuu EL34 A9 Tube Amp
anatech said this:

I should mention that you can use your computer sound card with some programs - BUT!, you need a front end for it. Something like a THD meter (HP 339A for example), or Bob Cordell's sound card front end. Most sound cards and inexpensive digital oscilloscopes will be damaged by waveforms exceeding their maximum input of 5 V peak for DC, 5 V p-p for AC signals. A 10X probe will buy you a 50 V peak, unless the button slips to X1 from X10 (glue the switch with epoxy!!). It is exceedingly easy to encounter 50 VDC peak in today's electronics. Tube amplifiers regularly exceed that limit at most test points.

So possibly 'the real thing' like the older HP digital scope mentioned above by DUG would be a better bet for a beginner?

 

[dangus]

A sound card with an optical input could be used with a cheap spdif ADC... search eBay for "Analog to Digital Audio Converter"