My Grand Tektronix Adventure

A fine spring Sunday morning a few years back found me down at the Adelaide Show Grounds Market hunting for fresh fruit, vegetables and seedlings, as is my wont. Behind that market and around a corner I stumbled upon another market – this one for second-hand goods – and my life was changed completely: on a shelf among the China dogs and knitted teapot cosies stood a Tektronix 564 analog storage oscilloscope in fine condition. I didn’t even stop to haggle – I put up the $75 asking price in cash and lugged it out of there before they realized they’d been suckered!
And so my grand Tektronix adventure began.
Back in the early 1970’s – in the old SAIT electronic engineering school on North Terrace – these top-of-the-line scopes were kept well away from bumbling undergraduates such as myself and reserved instead for senior academics. I never did get to lay a finger on one, although I do recall peering through the lab window at these in awe. Built between 1962 and 1968, these tube-based scopes were a masterpiece of exquisite engineering, marrying form and function and built for a lifetime.
This Tektronix 564 scope – at 10 MHz bandwidth – isn’t fast. But because the scope is completely analog what you see on the screen is what is really on the bench in front of you. The high persistence phosphor allows one to store waveforms for up to an hour on the top half of the display while running new traces on the bottom half for comparison.
But what this 560-series of scopes does have are two plug-in slots, the left-hand slot for the vertical beam drive and the right-hand slot for time-bases or horizontal beam drive. This ‘pluggable mainframe’ arrangement means you can drive the large sharp display with whatever signals you can come up with. Thus began my hunt on eBay for 2- or 3-series Tektronix plug-ins that would allow me to do all sorts of clever stuff.
I’m embarrassed to admit that I’ve probably cornered the world market for these plug-ins; they are now so cheap as to be irresistible, though getting them posted to Australia from the USA triples their price. Beyond the ordinary single, dual and quad vertical-axis amplifiers and the regular and delayed-sweep time-bases lies a wonderland of specialty modules that allow me to deploy such functions as differential comparators, differential amplifiers with 10uV/div resolution, sampling sweeps with 350ps resolution and a carrier amplifier for strain-gauge bridge monitoring. I’ve even got a plug-in spectrum analyser with a massive 1MHz bandwidth! Caught up in the fever of playing with all this old stuff, I paid US$220 for a massive 31 kg 600 W true dual-beam 565 Tektronix CRO that had to come by sea. Essentially two 560-series oscilloscopes in the one cabinet, it accepts the same series of vertical plug-ins. The Tektronix 565 has two completely separate time-bases built into it, and so is useful when working on circuits where some signals are completely asynchronous to one another.
I’ve got a few magnificent modern oscilloscopes, but what I really won from these old tube-based models is an education. Both scopes and plug-ins are eminently repairable using published circuits and manuals to be found for free on the BAMA Manual archive. Studying the schematics and the explanatory text teaches one the fundamentals of electronics, and it is only a deep grasp of fundamentals that allows one to come up with something truly new in the modern era.
Not bad for $75 in seed money.