-----Original Message-----
From: Tony Duell <ard_at_p850ug1.demon.co.uk>
To: Discussion re-collecting of classic computers
<classiccmp_at_u.washington.edu>
Date: Tuesday, November 23, 1999 9:43 PM
Subject: Re: Oscilloscopes
>> I agree but I would not recommend someone dropping a couple hundred bucks
to
>> fix an old 20Mhz scope as I am sure they would not limit their use
>
>It probably wouldn't cost anything like that much... Most older 'scopes
>are easy and cheap to repair.
>
We are talking about someone here who is *unable* to fix his own scope. I am
sure you or I could fix it for under $5 (providing the CRT and flyback are
good)... but in the real world most people *can't* fix their own test
equipment. In fact, most general repair shops aren't able to do a fair
job....
>> *exclusively* to vintage minis. A 20Mhz scope in RF/High speed logic
>> troubleshooting/design is totally useless. A 20Mhz scope isn't even very
>
>_Nonsense_. I've done a heck of a lot of troubleshooting on quite modern
>stuff using that 15MHz 'scope I mentioned earlier. It all depends on how
>you use your instrument and if you know how to interpret the results.
Tony, I can't see distortion in an oscillator at 61.25Mhz with a 20Mhz
scope.... And I have pioneered *alot* of code cracking on video signals and
that would not be possible with any old equipment.
You *can* do alot of troubleshooting with a 15Mhz scope... but, for
instance, I can't see distortion/FSK data on a122.7Mhz oscillator/FM
transmitter (that band should mean something to you ;-) ) with a 15Mhz
scope.
Each to his own... You obviously love working with old test equipment and
support old hardware. I don't see a lot of people out there like yourself
anymore.. [although I have met a few non-gui UNIX administrators that hate
my guts after tossing their servers for NT] .. I like working on the old
stuff; sometimes even with the old stuff... but I don't bring that into new
world work... That's just me.
>
>> good at looking at the color burst of a video signal in any detail.
Again, I
>> find most folks design/troubleshoot in a variety of areas and that's why
we
>> need scopes with all the toys. I don't see Tek making any more 20Mhz
boxes.
>
>Maybe not Tektronix, but there are still 20 and 30 MHz 'scopes in the
>catalogues. And most of them are horrible -- they don't trigger properly,
>etc. You'd be _much_ better off spending the money to fix up an old
>Tektronix than buying one of those. Of course if you can afford a new Tek
>with all the bells and whistles, well that's great!.
>
I agree, but old scopes are expensive to maintain for someone who is not
able to repair it himself.
>The other thing is that a Tektronix '20 MHz' scope will, in general
>display something useful for signals of a considerably higher frequency
>(I've 'pushed' a 50MHz 547 (_really old_) to at least 75 MHz). Yes, the
>amplitude calibration is off. All signals look like a sine wave. But you
>can still make measurements if you have to.
MY POINT! I was refering to RF work above... you don't just buy a scope for
old mini digital work.. If you buy an old scope/20Mhz you automatically
rule out most high frequency analog work and communications. Digital signals
look like sine waves.. ever tried to diagnose a problem with an RF circuit
with a minimum bandwidth scope??? The waveform looks like pure garbage..
Hence, the need for a *real* scope.
>
>At least one company seems to define an 'x MHz scope' as : If you turn
>the Y gain right up and apply the maximum allowed signal then you'll see
>_something_ at 'x MHz'. I am not joking...
>
Agreed , I have done it with my 2465 (yes, I have had to look at RF higher
than 300Mhz)... In fact, I use to use a dual trace Gould (100Mhz) on 200Mhz
work..... with minor grief. All depends on the application.
Where are you located in the UK?
>-tony
>
Received on Tue Nov 23 1999 - 20:22:29 GMT