551: Difference between revisions

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


Unlike the [[555]], it has only one set of horizontal deflection plates and  
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 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 [[545|545A]], 551, and 555 are identical.
The vertical amplifiers of the [[545|545A]], 551, and 555 are identical.
The 551 uses an L-C [[delay line]] for each vertical channel.


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 filament current for the tubes in the indicator unit is produced by a transformer in the indicator unit,
T750, Tektronix part number [[120-235]].
T750 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.
The external power supplies of the 555 and 551 are not interchangeable.
However, the cable that connects the power supply to the indicator unit is the same for the 551 and the 555.
It is Tektronix part number [[012-032]].


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.
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.

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