Analyzer was Re: KIM-1 repair advice wanted

[Tony Duell]

> > First thing would be
> >to connect a logic analyzer to see if the CPU is still running
> >a programm in ROM or not.
> 
> Hi
>  What is it with logic analyzers. Why not just an
> oscilloscope. In most cases, one can be farther along
> with an 'oscope in finding what is wrong by the
> time one can get an analyzer connected and setup.
> I've only had one time that I ever needed an analyzer
> and even that time, it didn't work well because
> of the complexity of the problem ( design not failure ).
>  I'll admit that I've often thought of making one
> of those address compare circuits to trigger the 'scope
> but by the time I'd get serious, I'd found the problem.
>  Am I alone here or does everyone else think that an
> analyzer is the ultimate tool?

The logic analyser is not the ultimate faultfinding device. In fact the 
ultimate faultfinding device isn't made by Tektronix, Agilent or Lecroy, 
it doesn't come from RS components, Farnell, or Digikey. As I've said 
many times before, it's called a brain :-).

A person with minimal test gear who knows what they are doing will easily 
beat an idiot with the most expensive 'scope and analyser in existance. 
Period.

That said, you do need to collect information from the unit under repair 
in order to find the fault. Now whether I would use a 'scope or a logic 
analyser depends on the problem and the device. A trivial example is that 
a logic analuser is uselss for sorting out an SMPSU, while a 'scope is 
not that useful in trying to figure out what's going on on a 16 bit bus.

AS to what I sue, I will admit I use my LogicDart a lot. That's a 
3-channel handheld logic analyser with one excellent feature. Rather than 
just recording 0 or 1, it records 0, 1, or undefined. The latter is very 
useful for finding marginal gates ;-).That instrumet is almost as easy to 
use as a logic probe, but tells you a lot more about the circuit under 
test. I do have other analysers with more input channels, and I am glad 
of them sometimes. But I don't use them that much.

Similarly with the 'scope, actually, I have a little Solartron 'scope 
that I use for most work. It's only 15MHz, but it'll find PSU ripple, 
look at chopper waveforms, etc. I have the good Tekky 555 that I use when 
it's needed, but most of the time it's easier to use the smaller 'scope.

-tony