511

Manuals – Specifications – Links – Pictures

The 511 was Tektronix' first oscilloscope, introduced in June 1947 but only the second product released by the young company – the first was the Type 101 Video Calibrator.

According to TekWeek March 23, 1984, "511" stood for 5-inch tube, 1 channel, 1st model. It sold for $795^{[Note 1]}, compared to $1,800 for a two-piece Dumont scope that was mostly pre-war technology.

An improved version, the 511A, was introduced in November 1948. Major improvements included a regulated power supply for CRT and calibrator (s.b.)

Howard Vollum was directly involved with the design of the 511.

Key Specifications

Bandwidth	5 Hz to 10 MHz (8 MHz with 2-stage amplifier); no DC coupling
Rise time	40 ns (50 ns with 2-stage amplifier)
Deflection	Without amplifier, 27 V per cm maximum, 200 V/cm minimum, DC or peak to peak AC. 1-stage amplifier, 2.7 V/cm maximum, 40 V/cm minimum. 2-stage amplifier, 0.27 V/cm maximum, 4 V/cm minimum.
Input	1 MΩ // 40 pF; 600 V max. DC+peak AC
Sweep	100 ns/cm to 10 ms/cm + variable; ×5 magnifier
Trigger	0.5 to 50 V (Peak) sine or pulse ≥50 ns
X input	DC coupled via 100 K potentiometer and sweep amplifier; 1.5 V/cm or less; DC to 800 kHz
CRT	5CP, 3 kV acceleration
Calibrator	Clipped sine wave of power line frequency, ranges 0-0.3, 0-1, 0-3, 0-10, 0-30, 0-100 Vp-p
Outputs	Sweep sawtooth, 20 Vp-p; Positive and negative gate, 40 Vp-p
Weight	511 – 29 kg (65 lb); 511A – 23 kg (50 lb);
Dimensions	15½" high, 12½" wide, 21 ½" deep
Power	511 – 180 W; 511A – 105-125 or 210-250 V, 50-60 Hz, 230 W

(511A unless noted otherwise)

There is also a 511AD, where the "D" in the model number indicates that it has an L-C delay line.

Prices

• $795 in 1948 (~$9,700 in 2023 dollars)

Internals

The 511 and 511A were normally furnished with P1 phosphor. P7 and P11 were optional, at no extra charge.

The 511/511A uses a standard CRT, the 5CP1A (P1), 5CP7A (P7) or 5CP11A (P11) below S/N 5100, the 5ABP from 5100 up. The vertical output of the 511A is a pair of 6AG7 tubes, AC-coupled to the vertical deflection plates.

Neither the 511 nor the 511A has a thermal cutoff. The 511AD was available through 1953.

The 511 was produced with serial numbers 101 to 454. The 511A has serial numbers 455 and up. The main difference between the 511 and the 511A is the power supply. In the 511 there are two power transformers, T1 and T2, both operating on 60 Hz mains power with their primaries in parallel. T1 produces the CRT anode and cathode voltages, as well as various other regulated and unregulated voltages. The CRT cathode and anode voltages in the 511 are simply rectified voltages from the secondary of T1. The lack of regulation means that variations in mains voltage results in variation of deflection sensitivity.

In the 511A, the CRT cathode and anode voltages are produced by a 2 kHz oscillator that is powered by the 511A's +225 V_DC regulated supply. This results in vertical deflection calibration that is independent of mains voltage.

The 511 and 511A use a 6AL5 tube (V3) as the disconnect diode for the sweep.

There was an option that added a 1 μs marker generator.

Delay

The Tektronix Type 1-AD-25 delay was available as a factory option for the 511. With the delay, the scope is a 511-AD. The delay is composed of 24 L-C sections. Even when ordered without the delay, the 511's chassis was pre-drilled for the delay so that it could be added later, in the field, without drilling. The delay could be switched in and out of the signal path, presumably to avoid the slight signal degradation the delay causes.

History

• See also https://vintagetek.org/tektronix-first-products/

Tektronix engineer Frank Hood recollects:

My first assignment was to build or modify some special instruments for Bonneville Power. They wanted a device that would detect and record any lightning strikes or arc-overs on the high voltage power lines running between Vancouver, Wash. and other cities such as Longview, Spokane, etc. They wanted to detect each event, in a fraction of a millionth of a second, then to send a pulse of energy down the defective line and measure the time it took to return, (this was an application much like radar). They wanted markers displayed at each mile and fraction of a mile so that they could determine the exact location of the fault. They needed to record a photographic image for latter study. Two or more such instruments were built. We called these Type 511B. They worked very well and were used for several years.

John Addis says:

The 511 was indeed somewhat crude. The vaunted calibrator which Vollum introduced to give people the sense that you could make real measurements is actually just a 60 Hz sine wave off the power transformer, not even a square wave, so it is completely unregulated. Fortunately for Vollum, both the calibrator and the CRT HV are unregulated. When the line voltage goes down, the scope sensitivity goes up (reduced HV makes beam converge less after plates). So the displayed calibrator amplitude is not very sensitive to line voltage.

Links

• Detailed article on 511A
• [Note 1] TekWeek March 23, 1984 says $595 but the advertised price was $795 (see below).

Pictures

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  Vollum scope - Electronics Magazine, April 1948

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  511 ad from September 1948

511A

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  511A ad from Electronics Magazine, November 1948, p.239

511AD

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  511AD

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  511AD

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  511AD

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  511AD

Some Parts Used in the 511

Page	Class	Description	Used in
0C3	Gas Discharge Tube (Voltage regulator)	105 V voltage reference	511
0D3	Gas Discharge Tube (Voltage regulator)	153 V voltage reference	511 • 511A • 513 • 514
2X2	Vacuum Tube (Dual Rectifier)	dual rectifier	511
5CP	CRT	Series of 5" CRTs with post-deflection acceleration	511 • 511A
5U4	Vacuum Tube (Dual Rectifier)	dual rectifier	511
5V4	Vacuum Tube (Dual Rectifier)	dual rectifier	511 • 160
6AC7	Vacuum Tube (Pentode)	RF pentode	511 • 511A
6AG7	Vacuum Tube (Pentode)	9 Watt power pentode	104 • 104A • 105 • 112 • 511 • 511A • 512 • 513 • 514 • 517 • 517A • 524
6AL5	Vacuum Tube (Dual Diode)	high-perveance dual diode	163 • 181 • 190 • 1M1 • 310 • 310A • 315 • 316 • 317 • 502 • 502A • 503 • 511 • 511A • 512 • 516 • 517 • 517A • 524 • 526 • 535 • 535A • 545 • 545A • 549 • 581 • 581A • 585 • 585A • 551 • C • T • Telequipment S52
6C4	Vacuum Tube (Triode)	VHF triode	190 • 511 • 511A • 517 • 517A
6J6	Vacuum Tube (Dual Triode)	high-frequency dual triode	104 • 104A • 161 • 511 • 511A • 512 • 517 • 517A
6L6	Vacuum Tube (Pentode)	beam power pentode	511
6V6	Vacuum Tube (Pentode)	12-watt beam power pentode	511