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Tektronix Scopes
A lot of firms, big names too, offered oscilloscopes claiming some exceptional features. But if one
was looking for uncompromising performances, the right choice was Tektronix or simply Tek.
Every model, from the small 3” service type to the large high-speed mainframe, was the best in its
segment, with its sharp and bright trace and its stable trigger. Tektronix took care of every detail,
from the look of the front panel, to the circuit design and to the top quality of components. The use
of distinctive ceramic strips, with a small reel of silver-loaded solder, somewhere inside the cabinet
to replace soldered parts, is part of the Tek legend.
B time base chassis of a 547 oscilloscope.
In this small overview, I show some oscilloscopes equipment of the legendary tube age, plus one
clone from Lavoie Labs.
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310A, 3” service oscilloscope
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502A, dual beam oscilloscope
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519, 1GHz bandwidth oscilloscope
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535, 5” single time base mainframe
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585/585A, 85MHz bandwidth mainframe
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LA-265, Lavoie mainframe equivalent to 545
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130LC, LC meter
310A – 3 inches service oscilloscope, 1958
This model was introduced in 1959 to replace the former model 310. DC to 4 MHz vertical
response, 0.1 to 50 V/division in 9 calibrated steps, plus 3 AC only high-sensitivity steps, down to
0.01 V/div, 2Hz to 3.5MHz. 90 ns risetime. 0.5 µs/div to 0.2 sec/div sweep range in 18 calibrated
steps, plus 5x magnifier, down to 0.1 µs/div, and variable control, uncal up to 0.6 s/div. Automatic,
internal, external or line trigger, AC or DC coupled. Internal voltage calibrator, 1 KHz square wave,
from 0.05V to 100V peak-to-peak in 11 steps.
AC power supply from 105 to 250V, 50 to 800Hz line frequency. DC supplies electronically
regulated. 1850V accelerating potential.
30 tubes, including CRT, plus 2 germanium and 12 silicon diodes; type 310 used selenium rectifiers
in the power supply. Tube list: 6DJ8, 6DJ8, 6DJ8, 6AU6, 12AT7, 6AL5, 6AN8, 6DJ8, 6DJ8,
6AU6, 6BH6, 6AU6, 6AU6, 6DJ8, 6CL6, 6CL6, 6BH6, 12AU7, 6AU6, 6BH6, 12B4, 5651, 6BH6,
12B4, 6BH6, 12B4, 12AU7, 6AQ5, 5642, 5642, 3WP1.
Tektronix Type 502A, Dual Beam Oscilloscope
The 502A oscilloscope was introduced in 1964 to replace the previous 502. Its characteristics can
be summarized as follows:
Dual-beam CRT
Differential or single-ended input.
Sensitivity down to 0.1 mV/cm at 100KHz bandwidth; from 5 mV/cm to 20 V/cm bandwidth is
greater than 1 MHz.
Sweep from 1 µs/cm to 5 s/cm in 21 calibrated steps; variable uncal up to 12.5 s/cm. Up to x20
magnifier.
Trigger sensitivity 2 mm deflection up to 200 KHz.
X-Y curve tracing capability, single beam hi-sensitivity or dual beam low-sensitivity
0.5 mV to 50 V in 6 steps internal calibrator
Type 502A uses 40 tubes, including the T5021-2 CRT, 23 transistors and 12 solid-state diodes.
Tektronix 519 – DC to 1 GHz oscilloscope
Introduced in 1961, 519 can well be considered a monument to the ingenuity of its designers. At the
time, no conventional amplifier could operate over such a wide band. Tektronix found the solution
of the problem, moving the vertical amplifier into the distributed deflection CRT. The T519 tube
has 27 vertical deflection plate pairs driven through the 27 taps along the built-in 125 ohm
transmission line. The signal propagates through the vertical deflection system, toward the screen,
at the same velocity of the electron beam, so that electrons are successively more and more
deflected before striking on the screen. The standard tube uses P11 high speed phosphor and 24 KV
accelerating voltage to make possible the photographic recording of single-shot events even at the
fastest sweep rate, 2 nanoseconds per centimeter. Remarkable and unique is the passive trigger take-
off, based upon eight 1:1 single turn transformers: primary windings are parallel connected all
around a cut section of the input line shield, while secondaries are series connected to give the
trigger signal, large about 10% of the input signal with only 0.7% attenuation of the same. Also
remarkable are the coiled 45 ns internal low-loss delay line, the sweep generator using a VHF
power tetrode, the countdown trigger oscillator, the avalanche rate generator and the vibrating reed
switch step generator.
Due to the GR coaxial connectors on the neck, for the input and the resistive termination, the CRT
was supplied with factory installed mu-metal shield and also with the serialized front bezel.
Characteristics:
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Vertical bandwidth: dc to 1000 MHz minimum at 3 dB. Risetime: less than 0.35 ns. Each tube is
individually calibrated and the actual risetime and deflection factor are engraved on the front
bezel.
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Time base: nine ranges from 2 ns/cm to 1000 ns/cm
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Rate generator pulses: rise time lower than 0.8 ns (0.5 ns typical)
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Calibrator: rise time 0.1 ns
Power supply: 110 or 220 VAC, 50 or 60 Hz, 650 W typical
Each oscilloscope mounts 47 tubes, 17 transistors, 51 diodes and 7 neon bulbs. T5191-11 CRT,
6688, 6DJ8, 12HG7, 6AU6, 6CW5/EL86, 12AL5, 4CX250F, 6AF3, 12AU6, 12BY7, 6080, 7734,
6AU5, 1X2B, 5642, 6AQ5. Some tubes may differ with the serial number or the revision level.
- Here the front bezels of the two 519 scopes available. The CRT on the left has 0.30 ns risetime and 9.3
V/cm deflection factor. The one on the right has 0.28 ns risetime and 8.1 V/cm sensitivity.
Tektronix Type 531A, about mid 1959
This was one of the simplest mainframe oscilloscopes from Tektronix. It was introduced in July
1959 to replace the previous 531, vertical bandwidth having been raised from 11 to 15 MHz.
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Vertical bandwidth from DC to 15 MHz; 23 ns risetime.
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Single time base; 100 ns/cm to 5 s/cm in 24 calibrated steps
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10 KV accelerating potential
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Accepts letter series plug-ins
Tek 585 / 585A, fast-rise mainframes
Here two of the fastest mainframe oscilloscopes from the late ‘950s up to the ‘960s. 585, left, was
introduced in 1959. Its characteristics were exceptional. DC to approximately 100 MHz vertical
bandwidth, 3.5 ns risetime; dual time-base, from 50 ns/cm (10 ns/cm with the 5x magnifier);
internal trigger was operated by any signal producing 2 mm deflection on the screen. The 585 was
first introduced with a special plug-in unit, type 80 with P80 probe. Later the type 81 adapter was
introduced, to accommodate letter-series plug-ins: the 585 mainframe in the picture mounts a 81
adapter and a CA plug-in.
The 585A, introduced in 1964, used a tunnel diode trigger, capable of operation to beyond 150
MHz. The 585A in the right picture accommodates a 82 plug-in, 4 ns rise-time, dual trace. The
performances of these oscilloscopes were obtained by an extensive use of distributed amplifiers and
by the proprietary CRT, with its distributed vertical deflection along 6 pairs of platelets, driven by
helix-wound transmission lines.
Lavoie LA-265A mainframe with LA-265-CA plug-in amplifier
The LA-265A is the equivalent of the Tektronix 545A mainframe, produced on a Lavoie design as
second source the 545A, probably in response to some Government’s needs. Characteristics are:
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DC to 30MHz bandwidth, 12 ns risetime
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Dual time base. Base A: 0.1 µs/cm to 5 s/cm in 24 steps, up to 12 s/cm uncal; 5x magnifier
allows 20 ns/cm sweep speed. Base B goes from 2 µs/cm to 1 s/cm in 18 calibrated steps
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Sweep delay variable from 1 µs to 10 s
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1 KHz internal calibrator, 0.2 to 100 V p-p, in 18 steps
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10 KV CRT accelerating voltage; 4 by 10 cm viewing window
Here are some pictures of this huge and fascinating oscilloscope. Bottom left, along the upper angle
brace and the back-panel, the balanced delay line, with its 50 trimming capacitors; close to the
bottom angle brace it is visible the vertical balanced distributed amplifier, with 12 6DK6, which is
also shown in the top right picture. Right center and bottom, the LA-265-CA plug-in amplifier.
As said, this oscilloscope looks like a well-done copy of Tek 545A. The size, the disposition of the
control knobs on the panel, the same characteristics, all recalls the Tek scope. The circuit, although
functionally identical, had been marginally redesigned. Lavoie used ceramic strips, which differed
from the Tek ones for having metal elastic clips inserted into the notches, rather than silver alloy
metallized notches in the ceramic body. Quite unusual are the impressive delay line, with 50
capacitive trimmers (I would like to see its adjust procedure!) and the CRT brightness stabilizing
device, a group of 31 neon bulbs potted in clear silicone rubber, which lights all the chassis inside.
So evident was the copy, to originate in 1971 a dispute for patent infringement: unfortunately, at the
date, Lavoie had already gone bankrupt.
Nevertheless, looking at the complexity of such an equipment and even if it was just a remake of an
already existing one, Lavoie Laboratories should well deserve a due memory. Unfortunately today
the sole trace of this manufacturer I found on the web is a picture of an old brick building,
surrounded by wild bushes, with a faded sign on the front.
Tektronix Type 130 L-C Meter and S-30 Delta Standards
This instrument has nothing in common with oscilloscopes but its manufacturer. It was intended for
small values of capacity or inductance. 5 ranges of capacitance, from 3 to 300pF full scale, and 5
ranges of inductance, from 3 to 300 µH full scale.
It came with the S-30 Delta Standards, a box with a set of reference values.