585: Difference between revisions

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The main difference is the impedance of the signal that passes
The main difference is the impedance of the signal that passes
through the interface from the plug-in to the mainframe.
through the interface from the plug-in to the mainframe.
In 530/540/550-series scopes, the plug-in expects the mainframe to be a high impedance load.
In 530/540/550-series scopes, the plug-in expects the mainframe to be a high impedance load,
Indeed, in those scopes, the plug-in is directly driving tube grids in the mainframe.
driving tube grids in the mainframe.
In 580-series scopes, the plug-in expects the mainframe to have a controlled impedance of 93 Ω per side (differential signal).
The [[580 Series plug-in interface]], on the other hand, presents a differential transmission line
input with an impedance of 93 Ω per side, going into the first distributed amplifier stage.  The
other end of this transmission line is returned to the plug-in for termination and biasing.
The [[580 Series plug-in interface|pin-out of the interface connector]] is also different,
The [[580 Series plug-in interface|pin-out of the interface connector]] is also different,
the 580-series pin-out being essentially flipped 180° from its  
the 580-series pin-out being essentially flipped 180° from its 530/540/550 series counterparts
530/540/550 series counterparts (''Signal Out'' is between pins 14 and 16 as opposed to between pins 1 and 3, etc.)  
(''Signal Out'' is between pins 14 and 16 as opposed to between pins 1 and 3, etc.)  


The [[81|Type 81]] adapter allows the use of letter-series and 1-series plug-ins in a 585.
The [[81|Type 81]] adapter allows the use of letter-series and 1-series plug-ins in a 585.
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made of a pair of miniature dual triode tubes.   
made of a pair of miniature dual triode tubes.   


Starting at serial number 1071, the miniature dual triode Schmitt trigger was replaced by a  
Starting at serial number 1071 (and sometimes retrofitted to earlier instruments), the dual-triode  
10 mA [[tunnel diodes|tunnel diode]] and a pulse amplifier made with an [[OC171]] Germanium PNP
Schmitt trigger circuit was replaced by a 10 mA [[tunnel diodes|tunnel diode]] AC-coupled to the
transistor.  The tunnel diode is AC-coupled to the base-emitter junction of the transistor.
base-emitter junction of an [[OC171]] germanium PNP transistor as a pulse amplifier.   
 
The slower "B" timebase uses a Schmitt trigger circuit.


=== Vertical Signal Path ===
=== Vertical Signal Path ===
Like the [[545]], [[551]], and [[555]], the 585 uses two [[distributed amplifier]]s in the vertical  
Like the [[545]], [[551]], and [[555]], the 585 uses two [[distributed amplifier]]s in the vertical signal path,  
signal path, one with seven differential [[6DJ8]] stages driving a helically-wound, differential [[delay line]],
one with seven differential [[6DJ8]] stages driving a helically-wound, differential [[delay line]], followed by  
followed by a five-stage differential distributed driver amplifier and a [[7699]] power stage driving the CRT.
a five-stage differential distributed driver amplifier and a [[7699]] dual tetrode power stage driving the CRT.


Unlike the other 500-series scopes, the 585 uses a CRT with [[distributed vertical deflection plates]],  
Unlike the other 500-series scopes, the 585 uses a CRT with [[distributed vertical deflection plates]],  
the [[T581]], enabling it to have both high sensitivity and fast risetime. Total acceleration voltage is 10 kV.
the [[T581]], enabling it to have both high sensitivity (~5 V/cm vertically) and fast risetime,
however, limiting vertical deflection to slightly over 4 cm. Total acceleration voltage is 10 kV.


Several improvements were published for the 585 circuitry, including the enhanced trigger circuit.  
Several improvements were published for the 585 circuitry, including the enhanced trigger circuit.  
If all of those changes are applied to a 585, it is essentially a 585A.
If all of those changes are applied to a 585, it is essentially a 585A.
After serial number 2585, the back termination of the final distributed amplifier output was made adjustable.
The manual says this (field-installable) modification is "required for proper operation of plug-ins with numbers above
[[81|Type 81]]".


===Power Supply===
===Power Supply===

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