Oscilloscope question

Joe R. rigdonj at cfl.rr.com
Wed Apr 13 21:46:51 CDT 2005


At 11:48 PM 4/13/05 +0100, you wrote:
>> The Tek 7000 series scopes are really, really, undervalued these days
>> for what they represent.  I got a fast 79xx mainframe at auction last
>> year for $5 because it had weird plugins (the Logic Analyzer plugins,
>> without the pods- useless) in it and didn't look much like a 'scope' to

    I just saw several DOZEN Tek 7000 series scopes thrown in the scrap. I
checked and found that they're nearly worthless now. A friend of mine put
one on E-bay starting at $20 and never got a bid on it! Looks like a
bargain to me!

>
>Actually, those pods are relatively 'benign' in that the signals to the 
>analyser are differential 10K-seriea ECL signals. It's not hard to make 
>up TTL-compatable input adapters, etc.
>
>Not as good as the real pod, but better than no analyser at all.
>
>> Students these days don't learn squat about using analog scopes, and
>
>Tell me about it. Actually, I am not sure what students _do_ learn these 
>days...

   I know for a fact that none of the colleges or universitys around here
even use scopes any more! If you want to find somebody that knows how to
use one you don't want a college graduate, you want an X-military
technician or a ham (amateur radio operator). VERY few of the electronics
hobbiest types even know how to use a scope these days.


>
>> there is a LOT you can do with one if you know how.  Delayed sweep,
>
>As I mentioned the other day, I've never used a DSO for real work. I've 
>always made do with an analogue scope, and I think I know how to do some 
>useful things with it. 
>
>My view is that you'll not get the best out of a DSO unless you fully 
>understand the use of an analogue 'scope 

  I agree. I think it much more important that user's learn how to a basic
scope (or any other instrument) and understand it and the measurement
techniques instead of trying to learn how to operate some overly
complicated and overly expensive fancy piece of gear.

(in much the same way that the 
>best users of CNC tools are darn good machinists on manual machine 
>tools, in the same way that the best designers using CAD systems are also 
>the best designers without CAD systems...). 
>
>> external trigger, etc. are there for a reason, and worth getting
>> acquainted with.  With delayed sweep and the Differential Comparator
>> plugin (introduces a DC offset so you can look at the 'important' part
>
>Now why do you think I have 1A5 plug-in for my 555 ? 
>
>> of the waveform at high gain) you can zoom in on tiny windows of
>> repetetive waveforms as well as (better than, actually) any digital
>> scope.
>
>And it's amazing how many signals can be made repetitive. A friend of 
>mine (a darn good hacker) debugged his homebrew 68K system with an old 
>Tekky analogue 'scope. He repeatedly pulsed the reset line to his system, 
>and connected that to the external trigger input of the 'scope. He then 
>looked at particular signals, 'scrolled through' them with the delayed 
>timebase and figured out what the processor was doing. 
>
>You can't always do tricks like that (which is why DSOs are sometimes 
>very useful), but many times you can.

  Why exactly do you need a DSO for something like that? I do things like
that all the time with my analog HP storage scope. It cost $20 at the local
university hamfest last summer. FWIW I like Tektronix scopes better but I
do like the storage feature on the HP.

  Joe


>
>-tony
>




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