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{{Oscilloscope Sidebar | |||
|manufacturer=Tektronix | |||
|series= | |||
|model=661 | |||
|summary=Sampling scope | |||
|image=661_5T1A_4S1_front.JPG | |||
|caption=Tektronix 661 | |||
|introduced=1961 | |||
|discontinued=(?) | |||
|designers=Norm Winningstad,Chuck Edgar,George Frye | |||
|manuals= | |||
* [[Media:070-324.pdf|Tektronix 661 Manual 070-324]] (early) | |||
* [[Media:070-0324-01.pdf|Tektronix 661 Manual 070-0324-01]] (late) | |||
* [[Media:tek_661_4s1_5t1_preliminary.pdf|Tek 661 4S1 5T1 Preliminary Manual]] | |||
<small> | |||
'''Alternate copies''' | |||
* [http://bama.edebris.com/manuals/tek/661 Tektronix 661 @ BAMA] | |||
'''Calibration''' | |||
* [[Media:tek_661_factory_cal_proc.pdf|Tektronix 661 Factory Calibration Procedure]] | |||
* [[Media:Tek 661 cal outline.pdf|Tektronix 661 Calibration Outline]] (PDF, OCR)]] | |||
'''Other''' | |||
* [ | * [[Media:Nucl_Instrum_Methods_TD_Induct_effects_1968.pdf|Inductance Effects on Capacitive Loading of a Tunnel Diode]] | ||
* [http:// | * [[Media:Ragsdale_661_1963.pdf|Self-Sampling System for Measurement of Picosecond Pulse Characteristics]], R.Ragsdale, 1963 | ||
* [ | </small> | ||
}} | |||
The '''Tektronix 661''' is a [[sampling oscilloscope]] that was [[introduced in 1961]]. | |||
It accepts two plug-ins, a sampling unit and a timing unit. | |||
{{MissingSpecs}} | |||
==History== | |||
The 661 project was led by [[Norm Winningstad]]. | |||
In "Winning with People: The First 40 Years of Tektronix", Marshall Lee writes: | |||
<blockquote> | |||
During the early stages of the transition from tubes to transistors, | |||
however, computer research focused on emitter-coupled logic circuits, or ECL circuits, | |||
which proved much faster than conventional circuits, but also demanded higher-speed measuring instruments, | |||
which meant a much wider bandwidth. | |||
In response to ECL research, by 1962 Winningstad's group had produced the Type 661 sampling oscilloscope, | |||
which provided the answer to high speed and screen resolution. | |||
</blockquote> | |||
In addition to Winningstad, [[Chuck Edgar]] and [[George Frye]] worked on the 661 design. | |||
==Plug-ins== | |||
Four sampling units were made: | |||
* [[4S1]] (0.35 ns rise time) | |||
* [[4S2]] (0.1 ns rise time) | |||
* [[4S2A]] (90 ps rise time) | |||
* [[4S3]] (uses [[P6038]] sampling probes) | |||
Three timing units were made: | |||
* [[5T1]] | |||
* [[5T1A]] | |||
* [[5T3]] | |||
There is also a set of calibration fixtures, [[067-0066-00]], consisting of one Vertical Test Load Unit and one Sweep Test Load Unit plug-in, but these were likely internal-only products for use in production and service as the 067-0066-00 manual says that ''067-0066-00 Test Load Units are not required for calibration of 661s in the field''. | |||
== Inter-module signals == | |||
The timing units use [[tunnel diodes|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 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: | |||
* 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 diodes|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, Tek part number 131-212, 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. | |||
== 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, but the | |||
661 uses a 24-pin version whereas the 500-series uses a 16-pin version | |||
of the connector. | |||
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]. | |||
==Pictures== | |||
<gallery> | <gallery> | ||
Tek 661 s-52 rise.jpg|661 with [[4S1]] and [[5T3]] fed by [[S-52]]. 2 ns/div with 10x horizontal expansion gives 200 ps/div. | |||
661 5T1A 4S1 front.JPG | front view | |||
661_front.jpg | front view | |||
661_top_int.jpg | top internal view | |||
Tek 661 block.png|Block Diagram | |||
661_trace.jpg | trace with 10 samples/cm and 2× horizontal expansion | |||
661_left_int.jpg | lleft internal view | |||
661_rt_int.jpg | right internal view | |||
Tek_661_rear.jpg | rear view (fan removed) | |||
Tek_661_solder.jpg | close-up of solder & inspection markings | |||
4s1_top.jpg|top view of 4S1 | |||
4s1_timing_pulse_connection.jpg | Coaxial interconnect from timing plug-in goes through the mainframe, into the 4S1, and ends here, at the sampler. | |||
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 | |||
Tek 661 ad 1963.png|Ad from 1963 | |||
</gallery> | </gallery> | ||
{{Plugins|661}} | |||
==Components== | |||
{{Parts|661}} | |||
[[Category:Sampling scopes]] | |||
[[Category:661 series scopes]] |