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The Tektronix 661 is a [[sampling oscilloscope]] that was [[introduced in 1961]].   
{{Oscilloscope Sidebar |
It accepts two plug-ins: a sampling unit and a timing unit.   
title=Tektronix 661 |
Four different sampling units were made:  
summary=Sampling scope |
image=661_5T1A_4S1_front.JPG |
caption=Tektronix 661 |
introduced=1961 |
discontinued=(?) |
manuals=
* [http://bama.edebris.com/manuals/tek/661 Tektronix 661 Manual (PDF)]
* [http://w140.com/tek_661_late.pdf Late Issue Tektronix 661 Manual (PDF)]
* [http://w140.com/kurt/4s1.pdf 4S1 manual without schematics]
* [http://w140.com/kurt/4s1/ 4S1 schematics]
* [http://w140.com/kurt/tek_4s2_schematics.pdf 4S2 schematics]
* [http://w140.com/kurt/tektronix_4s2.pdf 4S2 complete manual]
* [http://w140.com/kurt/tektronix_5t1a.pdf 5T1A manual]
* [http://w140.com/kurt/tektronix_5t3.pdf 5T3 manual]
* [http://w140.com/tek_661_4s1_5t1_preliminary.pdf Tek 661 4S1 5T1 Preliminary Manual (PDF)]
* [http://w140.com/tek_661_factory_cal_proc.pdf Tektronix 661 Factory Calibration Procedure (PDF)]
* [http://w140.com/Nucl_Instrum_Methods_TD_Induct_effects_1968.pdf Inductance Effects on Capacitive Loading of a Tunnel Diode]
* [http://w140.com/ragsdale_661_1963.pdf Self-Sampling System for Measurement of Picosecond Pulse Characteristics], R.Ragsdale, 1963
}}
The '''Tektronix 661''' is a [[sampling oscilloscope]] that was [[introduced in 1961]].   
It accepts two plug-ins, a sampling unit and a timing unit.   
 
Four sampling units were made:  
* [[4S1]] (0.35 ns rise time)
* [[4S1]] (0.35 ns rise time)
* [[4S2|4S2 and 4S2A]] (0.1 ns rise time)
* [[4S2|4S2 and 4S2A]] (0.1 ns rise time)
Line 11: Line 33:
* [[5T3]]
* [[5T3]]


== Inter-module signals ==
The timing units use [[tunnel diodes|tunnel diode]] triggering.   
The timing units use [[tunnel diodes|tunnel diode]] triggering.   
Two 50-ohm coaxial cables in the scope connect the sampling unit to the timing unit.   
Two 50 Ω coaxial cables in the scope connect the sampling unit to the timing unit.   
One of these cables sends the trigger pickoff signal (if available)
One of these cables sends the "internal trigger signal" from the sampling unit to the timing unit.  
from the sampling unit to the timing unit.
The other cable sends the "start sample signal" from the timing unit to the sampling unit, telling it when to sample.
The other cable sends the timing signal  
from the timing unit to the sampling unit,  
telling it when to sample.


The connectors used for the inter-module coaxial connections were made by Gremar.
The connector on the plug-in side is a [[Gremar connector|Gremar 8212A]].
The connector on the scope side is a Gremar 8205A.
When operating one or both of the plug-ins outside of the 661,
the timing unit can be fed an external trigger signal via the timing unit's front panel.
However, the sampling unit still needs the start sample signal from the timing unit.
The Gremar extension cable, part number 012-070 (shown below) enables that.
== Triggering modes ==
A 661 can be triggered in at least four distinct modes:
* The 4S1 uses a trigger pickoff transformer to produce the internal trigger signal that can trigger the timing unit. The 4S1 is the only 661 sampling unit that produces an internal trigger signal.
* An external trigger signal can be fed to the timing unit via its front panel. 
* The timing unit can be operated in in free-running mode and the resulting pulse signal can be the stimulus for the device under test.  This mode is similar to a TDR.
* The calibration signal generator in the 661 can be used as trigger source, as described below.
== Subsystems of the 661 ==
Other than the two plug-ins, the 661 mainframe essentially consists of four subsystems:
Other than the two plug-ins, the 661 mainframe essentially consists of four subsystems:
* power supply
* power supply
Line 25: Line 61:
* delayed pulse generator
* delayed pulse generator


The power supply is typical of  
=== Power Supply ===
Tektronix scopes of early 1960s.
The power supply is typical of Tektronix scopes of early 1960s.
An [[OG3]] tube is used as a
It is linear.
voltage reference for the +300V supply.
All power rectifiers are silicon diodes.
The other supply voltages use the +300V
An [[OG3]] tube is used as a voltage reference for the +300 V supply.
supply as their reference. The +19V and -19V supplies
The other supply voltages use the +300 V supply as their reference.
use BJT-based regulators.  The other regulators are tube-based.
The +19 V and -19 V supplies use BJT-based regulators.   
The other regulators are tube-based.
A 45 second delay tube is used so that plate voltage isn't applied to any tube in the 661
until the cathodes are hot.
The 661 has a 137°F/58 °C [[thermal cutoff]].
In practice, it doesn't run hot.


The indicator is a conventional X-Y indicator.
=== Indicator ===
The total CRT accelerating voltage is 3kV and
The indicator is a conventional X-Y indicator.
the vertical and horizontal amplifiers are  
The total CRT accelerating voltage is 3 kV.
relatively mild differential amplifiers made of [[6DJ8]] tubes.
The 661 uses a [[T5030]] CRT with P2 [[phosphor]].
The vertical amplifier has a feedback loop around it
The vertical and horizontal amplifiers are essentially the same,
that determines the gain.
each consisting of a two-stage differential amplifier.
The first differential stage is made of a pair of [[OC170]] germanium PNP bipolar junction transistors
driven single-endedly with emitters connected directly together (maximum voltage gain).
The second differential stage is made of both triodes of a [[6DJ8]] tube with cathodes connected directly together (maximum voltage gain).  
The vertical and horizontal amplifiers have feedback loops around them that determine their gain.


The amplitude/time calibrator is a Colpitts oscillator that uses a [[7119]]
=== Calibrator ===
tube. It produces clippped sine waves at frequencies from 100kHz to 100MHz and
The amplitude/time calibrator is a Colpitts oscillator that uses a [[7119]] tube.
amplitudes from 1mV to 1000mV. The output is 50-ohm [[Connectors#GR-874|GR-874]].
It produces clippped sine waves at frequencies
The signal from the calibration generator is available on the front panel and  
from 100 kHz to 100 MHz and amplitudes from 1 mV to 1 V.
is also sent to the timing generator through the multi-pin plug-in connector.   
The output is 50 Ω [[GR-874 connector]].
The signal from the calibration generator is available on the front panel
and is also sent to the timing generator through the multi-pin plug-in connector.   
This allows the timing plug-ins to select "CAL" as a trigger source.   
This allows the timing plug-ins to select "CAL" as a trigger source.   
In this mode, the calibration generator can be used as the stimulus for the device under test.   
In this mode, the calibration generator can be used as the stimulus for the device under test.   
In many situations, this eliminates the need for external triggering.
In many situations, this eliminates the need for external triggering.


The delayed pulse generator is a [[tunnel diodes|tunnel diode]] circuit  
=== Delayed Pulse Generator ===
that produces a negative-going 250mV pulse with a risetime of about 150 ps  
The delayed pulse generator is a [[tunnel diodes|tunnel diode]] circuit that produces a negative-going 250 mV pulse
and a pulse width of about 400 ns.
with a risetime of about 150 ps and a pulse width of about 400 ns.
The output is 50-ohm GR-874.
The output is a 50 Ω [[GR-874 connector]].
When a timing unit (e.g., a 5T1) triggers,  
When a timing unit (e.g., a 5T1) triggers, it sends a pulse through pin 10 of the J4 interconnect
it sends a pulse through pin 10 of the J4 interconnect
to the delayed pulse generator, which regenerates the pulse.
to the delayed pulse generator, which regenerates the pulse.
There are three versions of the 661 delayed pulse generator.
There are three versions of the 661 delayed pulse generator (serial numbers 101 through 2829, 2830 through 3459, 3460 and up).
The first is in serial numbers 101 through 2829.  
All three versions use a 50 mA, 6 pF germanium tunnel diode to generate the actual output pulse.
The second version is in serial numbers 2830 through 3459.
In early 661 production, a [[1N3130]] tunnel diode was usedThen it was replaced by a [[TD1081]].
The third version is in serial numbers 3460 and up.
The circuit versions also differ in how they bias and trip the output tunnel diode.
All three versions use a 50mA tunnel diode to generate the
actual output pulse.  The circuit versions differ in how they
bias and trip the output tunnel diode.


Based on the available schematics, the 661 appears to have been designed in 1961.   
Based on the available schematics, the 661 appears to have been designed in 1961.   
During what years was it manufactured?
:''During what years was it manufactured?''
Why is it that the 661 has a dedicated high-speed coaxial interface between  
:''Why is it that the 661 has a dedicated high-speed coaxial interface between the sampling unit the timing unit
the sampling unit the timing unit while later 560-series sampling systems ([[3S2]], [[3T77A]], etc.)  
while later 560-series sampling systems ([[3S2]], [[3T77A]], etc.) simply use the regular plug-in connector
are able to simply use the regular plug-in connector and mainframe wiring harness  
and mainframe wiring harness for routing trigger and timing signals between the two units?''
for routing trigger and timing signals between the two units?


Some 661s have a multipin connector on the rear panel,  
Some 661s have a 41 pin [[Bendix connector]], J5, on the rear panel,
perhaps to allow the 661 to be interfaced to low speed data acquisition equipment
perhaps to allow the 661 to be interfaced to low speed data acquisition equipment or a computer.
or a computer.
This is essentially a pass-through from J2 & J3, the secondary multi-pin connectors on the vertical & horizontal plug-ins.
These connectors carry switch position information (number, magnitude & units) and clock & gate pulses.
Not all plug-ins had this 2nd connector; the [[5T1A]] does, while the [[5T3]] does not. 


The 661 has a 137 degree Fahrenheit [[thermal cutoff]].   
The Tektronix [[012-064]] is a plug-in extension cable for the 661.
In practice, it doesn't run hot.
 
{{MissingSpecs}}
 
== Mechanical ==
The 661 is constructed similarly to late-model [[500-series scopes]].
The chassis is made of sheet aluminum.
Most wiring is on [[Ceramic_Strips|ceramic strips]].
The side panels come off like those of a [[545|545B]] or [[547]].
The plug-ins of a 661 are incompatible with any other Tek scope,
but the construction style is similar.
The 661, like the 500-series scopes, uses Amphenol 26-series connectors
for the electrical interface between plug-in and mainframe.
The sides and rear of the 661 painted identically to late-model
500-series scopes, i.e., Tek-blue wrinkle.
   
==Links==
 
* [http://readingjimwilliams.blogspot.com/2013/06/scope-sunday-45.html Reading Jim Williams: Scope Sunday #45]
* A 661 can be seen in the [https://www.youtube.com/watch?v=I9m2w4DgeVk Tektronix film on Transmission Lines].


* [http://bama.edebris.com/manuals/tek/661 Tektronix 661 Manual (PDF)]
==Pictures==
* [http://w140.com/tek_661_late.pdf Late Issue Tektronix 661 Manual (PDF)]
* [http://w140.com/kurt/4s1.pdf 4S1 manual without schematics]
* [http://w140.com/kurt/4s1/ 4S1 schematics]
* [http://w140.com/kurt/tek_4s2_schematics.pdf 4S2 schematics]
* [http://w140.com/kurt/tektronix_4s2.pdf 4S2 complete manual]
* [http://w140.com/kurt/tektronix_5t1a.pdf 5T1A manual]
* [http://w140.com/kurt/tektronix_5t3.pdf 5T3 manual]
* [http://w140.com/tek_661_4s1_5t1_preliminary.pdf Tek 661 4S1 5T1 Preliminary Manual (PDF)]
* [http://w140.com/tek_661_factory_cal_proc.pdf Tektronix 661 Factory Calibration Procedure (PDF)]
* http://w140.com/Nucl_Instrum_Methods_TD_Induct_effects_1968.pdf


<gallery>
<gallery>
Image:661_top_int.jpg|top internal view
661 5T1A 4S1 front.JPG  | front view
Image:661_front.jpg|front view
661_front.jpg | front view
Image:661_trace.jpg|trace with 10 samples/cm and 2x horizontal expansion
661_top_int.jpg | top internal view
Image:661_left_int.jpg|left internal view
Tek 661 block.png|Block Diagram
Image:661_rt_int.jpg|right internal view
661_trace.jpg | trace with 10 samples/cm and horizontal expansion
Image:4s1_top.jpg|top view of 4S1
661_left_int.jpg | lleft internal view
Image:4s1_timing_pulse_connection.jpg|Coaxial interconnect from timing plug-in goes through the mainframe, into the 4S1, and ends here, at the sampler.
661_rt_int.jpg | right internal view
Image:4s1_sampling_bridge.jpg|This is the sampler.  The GaAs sampling diodes are arranged in a diamond shape and are directly connected to the socket from the delay line.
Tek_661_rear.jpg | rear view (fan removed)
Image:4s1_delay_connection.jpg|The delay line is a coil of coax going from the trigger pickoff to the sampler.
Tek_661_solder.jpg | close-up of solder & inspection markings
Image:661_timing_interconnect.jpg|The 661 mainframe has two pieces of 50-ohm coax that connect the sampling unit bay to the timing unit bay.  The plug-ins engage with these interconnects when inserted.
4s1_top.jpg|top view of 4S1
Image:4s2_4.jpg|4S2 top view
4s1_timing_pulse_connection.jpg | Coaxial interconnect from timing plug-in goes through the mainframe, into the 4S1, and ends here, at the sampler.
Image:4s2_3.jpg|4S2 front view
4s1_sampling_bridge.jpg | This is the sampler.  The GaAs sampling diodes are arranged in a diamond shape and are directly connected to the socket from the delay line.
4s1_delay_connection.jpg | The delay line is a coil of coax going from the trigger pickoff to the sampler.
661_timing_interconnect.jpg | The 661 mainframe has two pieces of 50 Ω coax that connect the sampling unit bay to the timing unit bay.  The plug-ins engage with these interconnects when inserted.
4s2_4.jpg | 4S2 top view
4s2_3.jpg | 4S2 front view
Tek 661 extension.JPG | [[012-064]] plug-in extension cable for 661
Tek_gremar_extension_012-070.jpg | [[012-070]] Gremar Extension Cable
Tek 661 d992 mod.png | Mod described in June 1963 Service Scope regarding the delayed pulse generator
Tek 661 rear2.jpg|Rear panel of 661. J5 connector is on the upper left
Tek 661 rear J5 connector.jpg|J5 connector on rear panel of 661
Tek 661 late sn delayed pulse2.png|Delayed pulse generator, final circuit version
</gallery>
</gallery>
[[Category:Sampling scopes]]
[[Category:661 series scopes]]

Revision as of 18:28, 16 December 2018

Manuals – Specifications – Links – Pictures

The Tektronix 661 is a sampling oscilloscope that was introduced in 1961. It accepts two plug-ins, a sampling unit and a timing unit.

Four sampling units were made:

Three timing units were made:

Inter-module signals

The timing units use tunnel diode triggering. Two 50 Ω coaxial cables in the scope connect the sampling unit to the timing unit. One of these cables sends the "internal trigger signal" from the sampling unit to the timing unit. The other cable sends the "start sample signal" from the timing unit to the sampling unit, telling it when to sample.

The connectors used for the inter-module coaxial connections were made by Gremar. The connector on the plug-in side is a Gremar 8212A. The connector on the scope side is a Gremar 8205A. When operating one or both of the plug-ins outside of the 661, the timing unit can be fed an external trigger signal via the timing unit's front panel. However, the sampling unit still needs the start sample signal from the timing unit. The Gremar extension cable, part number 012-070 (shown below) enables that.

Triggering modes

A 661 can be triggered in at least four distinct modes:

  • The 4S1 uses a trigger pickoff transformer to produce the internal trigger signal that can trigger the timing unit. The 4S1 is the only 661 sampling unit that produces an internal trigger signal.
  • An external trigger signal can be fed to the timing unit via its front panel.
  • The timing unit can be operated in in free-running mode and the resulting pulse signal can be the stimulus for the device under test. This mode is similar to a TDR.
  • The calibration signal generator in the 661 can be used as trigger source, as described below.

Subsystems of the 661

Other than the two plug-ins, the 661 mainframe essentially consists of four subsystems:

  • power supply
  • indicator
  • amplitude/time calibration signal generator
  • delayed pulse generator

Power Supply

The power supply is typical of Tektronix scopes of early 1960s. It is linear. All power rectifiers are silicon diodes. An OG3 tube is used as a voltage reference for the +300 V supply. The other supply voltages use the +300 V supply as their reference. The +19 V and -19 V supplies use BJT-based regulators. The other regulators are tube-based. A 45 second delay tube is used so that plate voltage isn't applied to any tube in the 661 until the cathodes are hot. The 661 has a 137°F/58 °C thermal cutoff. In practice, it doesn't run hot.

Indicator

The indicator is a conventional X-Y indicator. The total CRT accelerating voltage is 3 kV. The 661 uses a T5030 CRT with P2 phosphor. The vertical and horizontal amplifiers are essentially the same, each consisting of a two-stage differential amplifier. The first differential stage is made of a pair of OC170 germanium PNP bipolar junction transistors driven single-endedly with emitters connected directly together (maximum voltage gain). The second differential stage is made of both triodes of a 6DJ8 tube with cathodes connected directly together (maximum voltage gain). The vertical and horizontal amplifiers have feedback loops around them that determine their gain.

Calibrator

The amplitude/time calibrator is a Colpitts oscillator that uses a 7119 tube. It produces clippped sine waves at frequencies from 100 kHz to 100 MHz and amplitudes from 1 mV to 1 V. The output is 50 Ω GR-874 connector. The signal from the calibration generator is available on the front panel and is also sent to the timing generator through the multi-pin plug-in connector. This allows the timing plug-ins to select "CAL" as a trigger source. In this mode, the calibration generator can be used as the stimulus for the device under test. In many situations, this eliminates the need for external triggering.

Delayed Pulse Generator

The delayed pulse generator is a tunnel diode circuit that produces a negative-going 250 mV pulse with a risetime of about 150 ps and a pulse width of about 400 ns. The output is a 50 Ω GR-874 connector. When a timing unit (e.g., a 5T1) triggers, it sends a pulse through pin 10 of the J4 interconnect to the delayed pulse generator, which regenerates the pulse. There are three versions of the 661 delayed pulse generator (serial numbers 101 through 2829, 2830 through 3459, 3460 and up). All three versions use a 50 mA, 6 pF germanium tunnel diode to generate the actual output pulse. In early 661 production, a 1N3130 tunnel diode was used. Then it was replaced by a TD1081. The circuit versions also differ in how they bias and trip the output tunnel diode.

Based on the available schematics, the 661 appears to have been designed in 1961.

During what years was it manufactured?
Why is it that the 661 has a dedicated high-speed coaxial interface between the sampling unit the timing unit

while later 560-series sampling systems (3S2, 3T77A, etc.) simply use the regular plug-in connector and mainframe wiring harness for routing trigger and timing signals between the two units?

Some 661s have a 41 pin Bendix connector, J5, on the rear panel, perhaps to allow the 661 to be interfaced to low speed data acquisition equipment or a computer. This is essentially a pass-through from J2 & J3, the secondary multi-pin connectors on the vertical & horizontal plug-ins. These connectors carry switch position information (number, magnitude & units) and clock & gate pulses. Not all plug-ins had this 2nd connector; the 5T1A does, while the 5T3 does not.

The Tektronix 012-064 is a plug-in extension cable for the 661.

Key Specifications

  • please add

Mechanical

The 661 is constructed similarly to late-model 500-series scopes. The chassis is made of sheet aluminum. Most wiring is on ceramic strips. The side panels come off like those of a 545B or 547. The plug-ins of a 661 are incompatible with any other Tek scope, but the construction style is similar. The 661, like the 500-series scopes, uses Amphenol 26-series connectors for the electrical interface between plug-in and mainframe. The sides and rear of the 661 painted identically to late-model 500-series scopes, i.e., Tek-blue wrinkle.

Links

Pictures