[sdiy] Logic Analyzer Advice

[Michael E Caloroso]

About 30 years ago, the major engineering companies in town were replacing
their bench measurement systems.  A lot of their Tektronix stuff appeared
in a surplus store so I grabbed a Tek 7834 scope chassis (now replaced with
a 7904) and a bunch of plugins.  Among the plugins is a 7D01 logic analyzer
which I had experience with.  It is a high level logic analyzer.  I also
grabbed the companion DF1 data formatter, P6451 pods, probes, and clips.
Everything works, still have them.

The 7D01 is only 16 bits wide (inadequate for today's embedded system
development), but years later I would uncover the power of a 7D01 in an
analog scope chassis.  My 7904 chassis has four plugin bays with the
capability of two independent time bases.  If I use the 7D01 as one time
base. I can use a vertical plus a horizontal plugin for the other time base
to form an analog scope function, giving me a mixed domain diagnostic
system.  This is a powerful tool for diagnosing a multiplexed analog stream
in a malfunctioning polysynth or audio processor.

The 7D01 has a word recognizer that generates a trigger when its condition
is met.  It can also accept an external clock.  So if I probe the logic of
the address and control lines of a polysynth, I can configure the word
recognizer (WR) to a specific analog signal of interest, route the WR
trigger output to the external trigger input of the horizontal plugin, and
now my analog scope can get a steady display of a signal of interest in a
multiplexed stream.  And I have a spare vertical input for probing other
related signals.

I cannot stress enough the value of a system like this.  It has solved
malfunctions with my Memorymoog, OB-X, OB-SX, and Four Voice.  If you run a
repair service and know your way around embedded systems, this is a pretty
powerful tool to have.  Today you can find a system like that for $1000 and
under.

The 7D01 displays a timing diagram of 4, 8, or 16 logic lines at a time at
digital TTL/CMOS/variable threshold levels with a variable highlight cursor
and position/magnifier for vertical and horizontal axis.  Since it is
always acquiring data, the data can be aligned post/pretrigger, or centered
and can be synchronous or asynchronous of the internal sample clock.
Sample interval is adjustable in discrete 5-2-1 intervals, or an external
clock can be used.  The DF1 formatter converts the digital display
in binary, octal, or hex formats and has mapping and two tables of 17 lines
of 16 bit words that can be used for reference and comparison.  Not bad for
a system introduced in the mid 1970s.

The other thing I like about the 7D01/DF1 - no menu system.  All the
controls are on the front panel.  I never have to worry about an LCD or
graphical display to replace.

MC

On Fri, May 16, 2025 at 10:31 PM Adam (synthDIY) <synthdiy at adambaby.com>
wrote:

>
>
> On 17 May 2025, at 10:44, Phillip L Harbison <alvitar at xavax.com> wrote:
>
> "If the only tool you have is a hammer, every problem looks like a nail."
> -- I think my professor for Differential Equations said that. It's so old
> I've started taking credit for it myself. ;)
>
>
>
> My old man has a lot of great old sayings - that's always been a
> favourite.
> The dawning look of understanding when you say it, in some appropriate
> situation, to someone who has never heard it before... just gold!
> A
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