551

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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. The vertical amplifiers of the 545A, 551, and 555 are identical. The 551 uses an L-C delay line for each vertical channel.

Like the 555, the 551 has two parts, the "indicator unit" containing the signal path electronics and CRT, and an external power supply unit. The external power supplies of the 555 and 551 are not interchangeable, however, the cable that connects the power supply to the indicator unit (part number 012-032) is the same for the 551 and the 555.

The filament current for the tubes in the indicator unit is produced by a transformer in the indicator unit, T750 (part number 120-235), that has seven isolated secondaries, each supplying 6.3 VAC. The indicator unit also contains the CRT circuit, which uses 5642 tubes and produces the +8650 V CRT anode voltage and the −1350 V voltage for the CRT cathode. The external power supply unit produces regulated DC voltages of −150 V, +100 V, +225 V, +350 V, and +500 V.

A factory modification, MOD 108A, was available for increasing the CRT acceleration voltage from 10 kV to 12 kV to improve trace visibility at high sweep rates, at the cost of reducing deflection sensitivity to 0.85 cm/Div. A graticule with 0.85 cm units was supplied.

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

Specifications

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.)
$1,850
($14,000)
$2,650
($20,100)
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

Links

Pictures


Some Parts used in the 551

Page Class Description Used in
5642 Vacuum Tube (Diode) directly-heated high-voltage rectifier 360 453 504 506 513 515 516 533 533A 535 543 543A 543B 545 545A 545B 547 551 555 567 575 647
6AL5 Vacuum Tube (Double Diode) high-perveance dual diode 181 535A 545A 581A 585A 551 316 317 502A 516
6DK6 Vacuum Tube (Pentode) high-frequency miniature pentode 180 503 513 514 541 543 545 551 555
T5511 CRT dual-beam CRT 551
T57 CRT dual-beam CRT 551