how to troubleshoot?

[Magnus Danielson]

From: harry <harrybissell at prodigy.net>
Subject: Re: how to troubleshoot?
Date: Sat, 13 Jan 2001 10:40:55 -0500

> Hi All  (mis me ???)
> 
> I'd go with a (gasp) good digital scope, and keep an old analog in reserve
> for the times when the digital LIES to you... and you need a sanity check.
> 
> A tech said to me:  : found the problem... its switcher noise hittinh the dac.
> What Frequency, I asked?  He didn't know so I went to show him...
> Measure the period....
> 
> Then I noticed that no matter what sweep speed... I got the same number of
> noise
> pulses on my screen.  Hmmm.... is this REAL....can it BE ???
> 
> Analog scope shows... white noise. Digital was aliasing it into a periodic
> waveform.
> 
> Digital is great for frequency, pulse width, lfo, envelopes... etc.  Roll mode
> will let
> you see your .001Hz triangle. NO analog will do that.

Right. Digital scopes is a mixed blessing. They can do stuff which
analog jobs just can't do. On the same time, few people really knows
how a digital scope works on the signal, so they can be confused. I
still want a modern analog scope next to the digital one. I have some
old bulky (read tubes) analog scopes elsewhere thought.

Filestorage is one of the good things about digital scopes. For time
and frequency measurements a scope is just a tool to know where you
should trigg.

Cheers,
Magnus