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4S1: Difference between revisions
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{{Plugin Sidebar | {{Plugin Sidebar | ||
|manufacturer=Tektronix | |||
summary=Dual trace sampling unit| | |series=661 | ||
image=4S1 front.jpg | | |type=4S1 | ||
caption=4S1 front view image | | |summary=Dual trace sampling unit | ||
introduced=1962 |discontinued=(?) | | |image=4S1 front.jpg | ||
|caption=4S1 front view image | |||
manuals= | |introduced=1962 | ||
|discontinued=(?) | |||
|designers= | |||
|manuals= | |||
* [http://w140.com/kurt/4s1.pdf 4S1 manual without schematics] | * [http://w140.com/kurt/4s1.pdf 4S1 manual without schematics] | ||
* [http://w140.com/kurt/4s1/ 4S1 schematics] | * [http://w140.com/kurt/4s1/ 4S1 schematics] | ||
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=== Sampling Bridge === | === Sampling Bridge === | ||
The sampling pulses are fed to a sampling bridge made of four [[sampling diodes|GaAs diodes]]. | The sampling pulses are fed to a sampling bridge made of four [[sampling diodes|GaAs diodes]]. | ||
These diodes are fragile and exact replacements are hard to find. They have however been | These diodes are fragile and exact replacements are hard to find. | ||
successfully [[Sampling diodes|replaced by modern Schottky diodes]], e.g. Agilent HSMS-28x series. | They have however been successfully [[Sampling diodes|replaced by modern Schottky diodes]], e.g. Agilent HSMS-28x series. | ||
=== Dual-trace and X-Y Modes === | === Dual-trace and X-Y Modes === | ||
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=== Trigger Amplifier === | === Trigger Amplifier === | ||
The 4S1 uses an unusual trigger amplifier with two trigger signal paths. One path is for low frequencies, | The 4S1 uses an unusual trigger amplifier with two trigger signal paths. | ||
the other for high frequencies. (A similar approach was also used in the main vertical signal path of the | One path is for low frequencies, the other for high frequencies. | ||
[[7A29]] several years later.) | (A similar approach was also used in the main vertical signal path of the [[7A29]] several years later.) | ||
From serial number 101 to 1349, the low frequency path starts with a 25 kΩ resistor that DC-couples | From serial number 101 to 1349, the low frequency path starts with a 25 kΩ resistor that DC-couples the input signal to a [[2N1429]] PNP emitter-follower stage. | ||
the input signal to a [[2N1429]] PNP emitter-follower stage. | |||
After that is a [[151-103]] NPN common-emitter. The high frequency path starts with a trigger pick-off | After that is a [[151-103]] NPN common-emitter. The high frequency path starts with a trigger pick-off | ||
transformer on the input. The pick-off signal feeds a common-base amplifier that uses a [[2N700]] PNP transistor. | transformer on the input. The pick-off signal feeds a common-base amplifier that uses a [[2N700]] PNP transistor. | ||
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From there, the trigger signal passes through the 661, and into a [[5T1]] or [[5T3]]. | From there, the trigger signal passes through the 661, and into a [[5T1]] or [[5T3]]. | ||
4S1 units with serial number 1350 and up use a slightly less complex trigger amplifier circuit, | 4S1 units with serial number 1350 and up use a slightly less complex trigger amplifier circuit, with a [[TA2333]] silicon NPN transistor amplifying the entire frequency range. | ||
with a [[TA2333]] silicon NPN transistor amplifying the entire frequency range. | |||
=== Comparison with S-1 Sampling Heads === | === Comparison with S-1 Sampling Heads === | ||
The sampler board in the 4S1 is roughly equivalent to a pair of [[S-1|S-1 sampling heads]]. | The sampler board in the 4S1 is roughly equivalent to a pair of [[S-1|S-1 sampling heads]]. | ||
A short piece of RG-174 coax connects the 661 timing pulse coaxial connector to the | A short piece of RG-174 coax connects the 661 timing pulse coaxial connector to the [[SMB connector]] timing pulse input on the 4S1 sampler board. | ||
[[SMB connector]] timing pulse input on the 4S1 sampler board. This signal triggers | This signal triggers a blocking oscillator which drives a [[snap-off diode]], D2004, which generates the fast falling edge for the channel A and B sampling bridges. | ||
a blocking oscillator which drives a [[snap-off diode]], D2004, which generates the fast | The 4S1 uses [[7586|7586 nuvistor triodes]] as high-impedance buffers between the sampling bridge and the amplification that follows. | ||
falling edge for the channel A and B sampling bridges. The 4S1 uses [[7586|7586 nuvistor triodes]] | |||
as high-impedance buffers between the sampling bridge and the amplification that follows. | |||
The 4S1 has a main chassis and sub-chassis that plug into it. | The 4S1 has a main chassis and sub-chassis that plug into it. | ||