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.
|CRT||T57 (T551) in early, T5511 in later (SN 2032+) models|
|Rise time with Type K||14 ns||12 ns|
|Acceleration Voltage||10 kV||10 kV|
|Filament Regulation||none||saturable core reactor|
| Price in 1965
| $2,650 |
|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|