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Tektronix 551
27 MHz scope
Tektronix 551

Produced from 1958 to 1972

Manuals – Specifications – Links – Pictures

The Tektronix Type 551, introduced in 1958, is a 27 MHz dual-beam scope that takes two letter-series and 1-series plug-ins. '

Unlike the 555, it has only one set of horizontal deflection plates and the trigger and sweep circuitry are built in to the mainframe. Like the 555, the 551 has an external power supply unit. The external power supplies of the 555 and 551 are not interchangeable. The vertical amplifiers of the 545A, 551, and 555 are identical.

The 551 uses an L-C delay line for each vertical channel.

A factory modification, MOD 108A, was available for increasing the CRT acceleration voltage from 10 kV to 12 kV. This improved trace visibility at high sweep rates.

Early 551 units used UHF connectors. Many were converted in the field to use BNC connectors.


CRT T57 (T551) in early, T5511 in later (SN 2032+) models
Comparison of 551 with 555
551 555
Rise time with Type K 14 ns 12 ns
Acceleration Voltage 10 kV 10 kV
Filament Regulation none saturable core reactor
Price in 1965
(2015 equiv.)
Indicator Weight 52 lb (23.6 kg) 68 lb (30.8 kg)
Power Supply Weight 42 lb (19 kg) 45 lb (20.4 kg)
Power Consumption 850 W 1050 W



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