310

The Tektronix 310 is a compact portable oscilloscope, designed by Frank Hood and John Kobbe, that was introduced in 1955.

Manuals – Specifications – Links – Pictures

It is a 4 MHz single-trace, single-timebase scope with a 3" (7.5 cm) round CRT.

A revised version, the 310A, was introduced in 1959. While the 310 used printed-circuit boards, the 310A returned to ceramic strip construction in the interest of reliability. Is this the only time that a Tek design was moved from PCB back to ceramic strip?

The Hickok company produced a clone of the 310A under a US military contract as the AN/USM89B.

Key Specifications

Bandwidth	4 MHz (3.5 MHz below 0.1 V/Div, AC coupled)
Rise time	90 ns (100 ns below 0.1 V/Div, AC coupled)
Sweep	0.5 μs/Div to 0.2 s/Div 1–2–5
Deflection	10 mV/Div to 50 V/Div, 1–2–5 (below 0.1 V/Div only AC coupled)
Input impedance	1 MΩ // 40 pF
X input	1.5 V/Div, 500 kHz, 100 kΩ
Z input	20 Vp-p at rear "CRT Cathode" binding post
Calibrator	0.5 Vp-p to 100 Vp-p, 1–2–5; 1 kHz
Calibrator	1 kHz output, up to 100 V
Power	175 W

P2 phosphor was standard. P1, P7 and P11 were also available.

Internals

The scope cabinet was hinged to allow it to be opened like a book and operated for access to the circuitry for service purposes.

Cooling

The 310 is a tube scope and consumes 175 watts, but it does not have a fan. It therefore tends to run hot, particularly when used in a hot environment with still air. It has a 165 °F (74 °C) thermal cutoff switch in series with the primary of the power transformer.

For extended use in one place, a tilted fan base, the FB310 (part number 016-012) was available. The fan base blows air upward through the perforated bottom panel of the 310. While the scope had universal primary wiring options, the fan base did not. Separate models were available for 115 V_AC or 230 V_AC operation.

The scope has feet on the rear panel to allow it to be operated on the floor with the front panel facing up, but the manual warns against prolonged operation in this orientation.

Components

The 310 is a nearly true pure vacuum-tube scope, but in the power supply there are some silicon rectifiers, and there is one germanium point contact diode in the circuit.

Early examples of the Tektronix Type 310A used commodity 3WPx CRTs. At some point in production, they switched to the Tek-made T3100 CRT, which is compatible with the 3WP2.

310A changes

Unlike later Tek instruments, where the incremental model designated by an “A” suffix only occurred with a significant specification or performance enhancement, the original 310 and 310A were essentially identical. They even shared the same manual and schematics. The main difference was the wiring construction. needs to be checked - different tubes used according to the manuals

The original 310 pioneered the use of circuit board construction, rather than the trusted ceramic strip point to point wiring. The circuit boards were two-sided, however, Tektronix did not use through-hole plating although this had been introduced in 1947. Rather, all of the holes for component mounting and interconnect contained a rivet which was expanded in a press before the components were installed in the board. The rivets themselves were not soldered to the copper foil traces, and relied on the pressure from the crimp to make contact. This proved to be extremely unreliable, with many intermittent connections resulting in high warranty- and after-warranty failure.

The 310A model essentially used the identical circuit design, but returned to the trusted ceramic strip construction method.

The 310A also replaced the selenium plate rectifiers in the power supply with silicon diodes. Tek offered a retrofit kit, to be installed in the service centers, to upgrade older scopes with selenium rectifiers.

Other changes during production

During the lifespan of the 310, Tek evolved its color scheme. The original 310 scopes had a case painted with a blue metallic hammer tone color. Later units moved to the crinkled “Tek Blue” color still in use today.

Like most old Tektronix devices the mains transformer holds an indefinite(!) warranty.

Links

• Richard Sears: Tektronix 310 and 310A
• A Tek 310 restoration @ YouTube: Part 1 / Part 2

Pictures

310

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  Right front

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  Front

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  Rear

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  Model

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  Right rear

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  made for IBM

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  top inside

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  left inside

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  right internal

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  rear

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  bottom

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  right external

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  left external

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  310 on fan base

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  Carrying bag for 310, left

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  Carrying bag for 310, top

310A

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  Front view

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  Right internal

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  Folded off internal

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  Left internal

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  Top internal

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  Bottom special slot to access sweep trigger tubes

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  Bottom special slot to access sweep trigger tubes

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  Rear view

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  310A

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  310A

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  310A Left Internal

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  310A Right Internal

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  310A Right Internal, operating

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  310A top

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  310A rear

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  310A right internal

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  310A with silicon rectifiers

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  Case for 310A

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  310A in case

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  Tek 310A with case

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  310A inside carrying bag, exposed cushion

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  indefinite warranty to the Tektronix manufactured transformer

Hickok AN/USM89B

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  Front view

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  Side view

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  Type plate