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Tektronix 315
"Portable" tube scope
Tektronix 315

Produced from 1952 to (?)

Manuals – Specifications – Links – Pictures

The Tektronix Type 315 and 315D are single-channel oscilloscopes introduced in September 1952. They use 3WP2 3-inch CRTs. Later instruments use the Tek-made T3100-xx CRT.

Historic Context

Tektronix engineer Frank Hood recollects:

We started to move into the new Sunset plant in June of 1951. In the same year I started the design work on our first compact scope, the Type 315. This instrument had several innovative features. One was a sweep circuit designed by Dick Ropiequet which was several times more stable and accurate then any other then in use. With this circuit, the actual time of the sweep could be calibrated with such accuracy that we decided to start calling it a “TIME BASE”. The vertical amplifier was also more stable and accurate. A man in our test department, John Kobbe, suggested a direct coupled unblanking circuit. Another employee, Ted Goodfellow, a musician with ceramics as a hobby, suggested making a ceramic strip with silvered notches to act as insulator and support for the components. This smaller scope had less space on the front panel for the necessary controls. A Machinist, Jim Morrow, suggested combining some of the controls, by making them co-axial (that is, a shaft within a shaft and separate knobs.) We tried to purchase such controls but could find no one interesting in making them, so Jim machined sample controls. He even machined the dies to produce our own plastic knobs. All these suggestions were incorporated in the 315. Several patents were granted, which later led to a patent infringement suit which we brought against the Government (we eventually won the lawsuit)."

Key Specifications

Bandwidth DC to 5 MHz


Case Design

The 315 is mechanically similar to early 500-series monolithic scopes such as the 511A. The scope slides out of the case instead of having removable side covers as were used in the later 53x and 54x, and the 55x, 56x, 57x, and 58x designs.

3" CRT

The move to use a 3” CRT rather than a 5” was to produce a “portable” oscilloscope, which the 315-D was promoted as. With dimensions considerably smaller than the 5” models and only weighing a modest 36 pounds, it offers a lot of performance in a small package. In 1956, Tek introduced a rack mount version, the 315R. One has to wonder what the benefit of a 3" screen is when it was packaged as a rack sized instrument. Instruments originally used a purchased 3WP_ CRT. A mod was published in 1964 substituting the Tek-made T3100 CRT, part numbers 154-0362-00 through 154-0366-00, depending on the phosphor.

Delay Line

As with earlier 5” Tektronix scopes, the “D” suffix indicates the inclusion of a delay line in the vertical signal path. The delay line resides between the pre-amplifier, where the trigger signal is picked off and the final vertical amplifier. The delay line allows time for the sweep to start and the unblanking to turn the trace on slightly before the trace is deflected, so the user can see all of the rising edge of the signal which triggered the scope. The original 511, Tek’s first scope sold, did not have a delay line. It was added with a few other circuit enhancements to become the 511-AD model.


The delay line was offered as a “delete” option on early scopes, with the version without the delay line selling for $50 less. Apparently most customers ordered the delay line versions, and the 315 was the last scope introduced with the D suffix. Even so, the 1953 catalog, which was the first the 315-D appeared in, did not list the version without the delay line. It is quite possible that no plain 315 models were ever sold.



315 D

315 R


Some Parts Used in the 315

Part Part Number(s) Class Description Used in
12AT7 154-0039-00 Vacuum Tube (Dual Triode) dual high-gain triode 161 180 310 310A 315 316 360 502 502A 511A 512 513 513D 514 514AD 514D 516 524 529 RM529 544 546 547 556 565 570 3A2 75 3A75 1M1 A B C G H K L ML M N K R S Z
3WP 154-0059-00 CRT series of flat-faced 3" mono-accelerator CRTs 315 310 360 Telequipment S31
6AK6 154-0015-00 Vacuum Tube (Pentode) power pentode 315
6AL5 154-016 154-0016-00 154-0038-00 Vacuum Tube (Dual Diode) high-perveance dual diode 163 181 190 1M1 310 310A 315 316 317 3B1 3B1S 3B2 3B3 3B5 502 502A 503 511 511A 512 516 517 517A 524 526 535 535A 545 545A 549 551 565 570 581 581A 585 585A C T Telequipment D56 Telequipment S52
6BQ7 Vacuum Tube (Dual Triode) dual triode 315
6BQ7A 154-028 154-0028-00 157-0022-00 157-0003-00 Vacuum Tube (Dual Triode) dual triode 107 163 181 310 315 316 360 524 531 532 535 536 541 545 570 T
6U8 154-0033-00 Vacuum Tube (Triode/Pentode) triode-pentode combo 130 160 163 310 315 316 524 535 545 T
T3100 154-0362-00 154-0363-00 154-0364-00 154-0365-00 154-0366-00 154-0058-01 154-0059-01 154-0060-01 154-0061-01 CRT 3" CRT 310 310A 315 360