Ode to the Oscilloscope

-March 27, 2015

Having been a teenager in the 1960s, and with popular tunes of that decade still in my head, I offer a lyrical rewrite of one of them, with apologies to the author of the ‘60s hit tune, "Hotrod Lincoln". (“You’ve heard the story of the great car race, where Fords and Lincolns were settin’ the pace ¼) This ode has gone through some refinement, and here is the latest version.

 


You've heard the story of the bandwidth race,

Where ‘scopes and counters were setting the pace;

Well that story is true, I'm here to say;

I was using a 555A.

 

It's got a graticule, all lit up,

That front-panel claptrap makes it look tough.

It's got plug-ins, uses ‘em all;

Has snappy risetime, and also fall.

 

With a dual-beam display at reasonable cost,

And forty-eleven knobs, you can really get lost;

It's got a dual-delayed timebase, but I ain't scared,

The trace is sharp; the probes are fair.

 

Pulled out a new project late one night,

The test equipment was burning bright,

I started driving a wideband amp,

To see which stage I needed to damp.

 

When all of a sudden in the blink of an eye

A jumble of waveforms passed me by,

And I said, "Wow, that's a marvel to me!"

Pretty soon a square-wave was all I could see.

 

Now the waveform time-scale made no sense;

The scope display looked like a picket fence.

I slowed it down and was glad to know

That it wouldn't alias like a DSO.

 

Now the boss was ribbing me for being behind,

So I thought I'd make the probes unwind;

Took the volts per div knob, and man alive!

I cranked it up to a setting of five.

 

Powered the wideband amp again,

And drove it with a function gen,

Set the amplitude knob to three or four,

The levels were hitting the ceiling and floor.

 

Smoke was coming from out of the load

When I set the trigger to hf mode;

The power bandwidth was looking right;

Nearly approaching the speed of light.

 

 

I tweaked the circuit here and there,

Replaced a cap and transistor pair;

Got the speed I needed with room to go;

Manufacturing would be glad to know.

 

The task was finished, the specs first-rate,

The customers called, said the amp worked great;

I got a promotion, moved out of L.A.,

And I credit success to that '55A!

 

Notes:

 

The Tektronix 555A was a dual-beam (not merely dual-trace) oscilloscope, made with electron tubes. It was such a large and power-hungry ‘scope that the power supply was in a separate enclosure. With two beams, the CRT was essentially two CRTs in one and the 555 was nearly two ‘scopes in one. Whether there ever was an “A” version or not, it was invoked here by poetic license to achieve rhyming.

 

In the ‘60s, there really was a bandwidth race. The performance of some test instruments depends on speed, mostly oscilloscopes and counters. For a while (extending into the 1970s) H-P pulled ahead of Tektronix, until the Tek 7904 (500 MHz) and 7104 (1 GHz) ‘scopes were introduced. After that, ‘scopes went digital and a new kind of race has put H-P (by whatever name) back in the running.

 

In the electron-tube days of ‘scopes, a different trigger generator scheme was used than in later transistor ‘scopes which were based on a comparator with hysteresis and RS flip-flops. Trigger generators synchronize the start of a CRT sweep with a particular point in the cycle of a repetitive waveform. The older scheme was more like the phase-locking synchronization of television, and the high-frequency (hf) mode enhanced it at faster sweep speeds.

 

The original hit tune was kind of a “rap” song before its time and was not about electronics but was about high-performance automobile technology admired by teenage youth in southern California. They would increase the capabilities of their commercially-available vehicles through custom modification, sometimes paying insufficient attention to the undesirable consequences, as expressed in the original lyrics of this song. Adults nowadays do the same, though with the entire ecosphere, and are not limited merely to automobiles.

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