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The Tektronix 647A is a 100MHz scope that is designed to operate in a wide range of temperatures.  It takes two plug-ins, one for vertical, one for horizontal/sweep.  It uses 10-series and 11-series plug-ins.  The plug-ins
{{Oscilloscope Sidebar
resemble those that go in a 560-series scope, like the 3A3 and 3B2 plug-ins, but they are quite different
|manufacturer=Tektronix
are not at all compatible.  The 647A contains vertical and horizontal amplifiers, whereas in the 560-series,
|model=647
the plug-ins drive the deflection plates directly.  The 647A followed the Type 647, which is similar
|series=647
but has 60MHz bandwidth. There is also an RM647A.
|summary=50 MHz scope
|image=647a_1.jpg
|caption=647A front view
|introduced=1963
|discontinued=1967
|designers=Oz Svehaug;Oliver Dalton;Jim Knapton;
|manuals=
* [[Media:070-370.pdf|Tektronix 647 Manual]]
* [[Media:Tektronix RM647 schematics.pdf|Tektronix RM647 schematics]] (large format)
* [[Media:Tektronix 647 tentative specifications.pdf|tentative specifications.pdf]]
* [[Media:120_0332.pdf|Tektronix 647 HV transformer winding data]]
* [[Media:Tek 647 notes.pdf|Type 647 Notes]]
* [[Media:Tek 647a cal outline.pdf|Tektronix Type 647 and 647A Calibration Outline]] (OCR)
<small>
'''Alternate copies'''
* [https://bama.edebris.com/download/tek/647a/tek%20647a.djvu Tektronix 647A Manual] (DjVu @ BAMA)
}}
The '''Tektronix 647''' is a 50 MHz oscilloscope with plug-ins for both vertical and horizontal deflection.   
It was introduced in late 1963, along with a minimal set of plug-ins, and replaced by the higher bandwidth [[647A]] in 1967.
Except for the CRT and the rectifiers in the HV power supply, the 647 is all solid state.


The vertical amplifier contained in the 647A indicator unit (mainframe) is made of
The original 647 project leader was [[Oz Svehaug]] in 1962. From 1963 onward, [[Oliver Dalton]] took over.
NPN and PNP bipolar transistors. The output transistors, Q484 and Q494,  
are selected 2N3866 NPN transistors.
The datasheet for the 2N3866 lists Ft as 800MHz and specifies an absolute maximum value of Vceo
of 30V. The quiescent value of Vce on Q484 and Q494 is about 30V.  So it seems likely that the
selection process for these transistors involved testing their performance at the high end
of their specified voltage range, and probably beyond.


The power supply of the 647A is all solid state, with a zener voltage reference and NPN pass transistors
The intent was to offer a higher performance scope in a small form factor, roughly the size and weight of the [[560-series_scopes|560 series]]. 
at the outputs.
It was promoted as “ruggedized” with an extended operating temperature range, and higher shock and vibration ratings than previous lab grade instruments.


The horizontal amplifier in the 647A uses selected 2N3119 NPN bipolar transistors for the output.   
The 647 uses 10 series vertical and 11 series time base plug-ins. 
These are specified as having and Ft of 250MHz and a Vceo max of 80V.   
At introduction, the [[10A2]] a dual channel 50 MHz vertical, [[11B1]] single time base, and [[11B2]] dual time base were offered.   
The [[10A1]] 45 MHz differential comparator was introduced in 1965, the [[10A2A]] amplifier in 1967.
The 10 and 11 series plug-ins are unique to the 647 and 647A.   


The interface between the vertical plug-in and the indicator unit is a 93-ohm controlled-impedance
{{BeginSpecs}}
connection. This is in contrast to the 500-series scopes, which appear to
{{Spec | Bandwidth            | DC to 50 MHz with [[10A2|10A2 plug-in]], 45 MHz with [[10A1]] (35 MHz at <5 mV/div) }}
the plug-in as a high impedance. For example, there is a cathode follower immediately after the
{{Spec | Rise time            | 5.8 ns with 10A2, 7.8 ns with 10A1 (10 ns at <5 mV/div)}}
plug-in connector in a 547.  Notable exceptions are the 585 and 585A, which interface the signal
{{Spec | CRT                  | [[T6470]], P31 std / P11 opt., 6 cm × 10 cm, 14 kV acceleration }}
from plug-in to the scope at a 93-ohm impedance, like the the 647A.
{{Spec | Power                | 108/115/122/216/235/244 V<sub>AC</sub> ±10%,selected via primary voltage selector and voltage range selector switches, 50 Hz to 60 Hz; 185W with [[10A2]] & [[11B2]]  plug-in }}
{{Spec | Operating Temperature | –30 C° to +65 C°}}
{{Spec | Cooling              | AC Fan (only in rack variant) }}
{{Spec | Thermal Protection    | Automatic resetting thermal cutout, in case internal temperature exceeds safe operating level }}
{{Spec | Weight                | 18.4 kg (40.5 lbs) }}
{{EndSpecs}}


Is it the only scope to use those plug-ins? It is unusual to see only one scope in what appears to be the beginning of a series. Was it discontinued because of lack of demand?  What replaced it?
==Internals==
Unlike the threaded knob used for retaining the [[letter-series and 1-series plug-ins|530/540 series plug-ins]], the 647 uses a lever-actuated cam mechanism.  
The single lever both engages and disengages the plug-in with a quick, smooth motion. 
Many users considered it to be the best plug-in retaining system Tek had ever offered.


The 647 is similar to the 647A, but the bandwidth is 50MHz.
Unlike the [[560-series_scopes|560 series]] where the plug-ins directly drive the CRT deflection plates, the 647 has amplifiers for both the vertical and horizontal signals in the mainframe. 
In addition to supporting the higher bandwidth, the amplifiers provide a normalized gain at the plug-in interface, eliminating the need to adjust the gain or sweep cal every time a plug-in was swapped.


* [http://w140.com/kurt/647.pdf Tektronix 647 manual]
The 647 has a 140 ns [[delay line]] between the vertical plug-in connector and the input of the vertical amplifier. 
The interface between the vertical plug-in and the mainframe is a 93 Ω controlled-impedance connection. 
This is in contrast to the [[500-series scopes]], which appear to the plug-in as a high impedance.
 
The horizontal and vertical plug-ins are not electrically interchangeable. 
Only a 10 series plug-in will work in the vertical compartment, and only a 11 series time base will work in the horizontal compartment. 
X-Y mode requires the use of the external horizontal input in an 11 series time base.
 
The 647 uses the [[T6470]] CRT with electromagnetic [[trace rotation]] and 14 kV total accelerating voltage.
The HV power supply contains five [[5642]] rectifier tubes: three for the +11.2 kV CRT anode supply, one for the -2.2 kV CRT cathode, and one for the -2.2 kV CRT grid/blanking. 
 
The calibrator in the 647 is based on a 4 kHz crystal, which is divided down to 1 kHz ±1 Hz.
 
The solid extender for 647 plug-ins is the [[013-077]].
 
==Pictures==
===647===
<gallery>
Tek 647 10a1 11b2.jpg | 647 with [[10A1]] and [[11B2]]
Tek 647 right.jpg    | 647 Right Side
647 MOD165K.JPG      | 647 with MOD165K
</gallery>
 
===647A===
<gallery>
647a_1.jpg  | 647A Front View
647a_2.jpg  | 647A Left View
647a_4.jpg  | 647A Right View
647a_3.jpg  | 647A Rear View
Tek 647a front.jpg | 647A with [[10A1]] and [[11B2|11B2A]]
Tek 647a left.jpg  | 647A
Tek 647a rear.jpg  | 647A
Tek 647a rear connections.jpg | 647A rear connections
Tek 10a2a 11b2a.jpg | [[10A2 | 10A2A]] and [[11B2 | 11B2A]] in 647A
Tek 647a rear2.jpg  | 647A
Tek 647a right internal.jpg | 647A
Tek 647a left internal.jpg  | 647A
Tek 647a rear ps.jpg | 647A
Tek 647a trace6.jpg  | 647A
Tek 647a trace5.jpg  | 647A
Tek 647a trace4.jpg  | 647A
Tek 647a trace3.jpg  | 647A
Tek 647a trace2.jpg  | 647A
Tek 647a trace1.jpg  | 647A
</gallery>
 
===RM647===
<gallery>
RM647_1.JPG  | RM647 Front View
Tek rm647.jpg | RM647
</gallery>
 
==Components==
{{Parts|647}}
{{Parts|RM647}}
 
[[Category:Introduced in 1963]]
[[Category:647 series scopes]]
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