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{{Instrument Sidebar
|manufacturer=Tektronix
|model=122
|class=Amplifier
|series=
|summary=low-level preamplifier
|image=Tek 122 x.jpg
|caption=Tek 122 early model
|introduced=1950
|discontinued=(?)
|designers=
|manuals=
* [[Media:070-246.pdf|Tektronix 122 and 125 Manual]]
* [https://w140.com/brophy_122_mod.pdf Low Noise Modifications of the 122]
}}
The '''Tektronix 122''' is an external low-frequency low-level preamplifier.   
The '''Tektronix 122''' is an external low-frequency low-level preamplifier.   


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The input is differential, using an [[XLR connector]].  The output is through a [[UHF connector|UHF (SO-239) connector]], single-ended.   
The input is differential, using an [[XLR connector]].  The output is through a [[UHF connector|UHF (SO-239) connector]], single-ended.   
The amplifier electronics are on a plastic board with metal studs where components are soldered in place.   
The amplifier electronics are on a plastic board with metal studs where components are soldered in place.   
The board is mechanically isolated from the case by four rubber bushings.
The board is mechanically isolated from the case by four rubber bushings. The 122 is the only Tektronix product ever made that has a rotary two position power switch.


The 122 has four stages of amplification.   
The 122 has four stages of amplification.   
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The second stage is a [[12AU7]] differential amplifier, differentially driven by the first stage.   
The second stage is a [[12AU7]] differential amplifier, differentially driven by the first stage.   
There are DC blocking capacitors between plates of the first stage and the grids of the second stage.   
There are DC blocking capacitors between plates of the first stage and the grids of the second stage.   
The second stage is coupled to the third stage by capacitors,  
The second stage is coupled to the third stage by capacitors, which can be switched to select the low-frequency cutoff frequency.  
which can be switched to select the low-frequency cutoff frequency.  
The third stage is a common-cathode amplifier formed from one half of a 12AU7 dual triode tube.   
The third stage is a common-cathode amplifier formed from one half of a 12AU7 dual triode tube.   
The plate load resistors of the third stage amplifier are shunted by switchable capacitors,  
The plate load resistors of the third stage amplifier are shunted by switchable capacitors, allowing the high-frequency cutoff to be selected.   
allowing the high-frequency cutoff to be selected.   
The resulting signal is buffered by a cathode-follower stage formed from the other triode in the third stage's 12AU7 tube, biased at 1.8 mA plate current.   
The resulting signal is buffered by a cathode-follower stage formed from the other triode in the third stage's 12AU7 tube,  
biased at 1.8 mA plate current.   
The output impedance is rated to be about 1000 Ω.   
The output impedance is rated to be about 1000 Ω.   


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The power requirements of the 122 are:
The power requirements of the 122 are:
* +135V at 5ma
* +135 V at 5 mA
* -90V at 4ma
* -90 V at 4 mA
* 6.3V at 0.9A
* 6.3 V at 900 mA


The 122 appears in three form factors:
The 122 appears in three form factors:
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* RM122 (rack mount, horizontal orientation, with wide front panel for mounting mounting in a standard 19" rack, later called "R122")
* RM122 (rack mount, horizontal orientation, with wide front panel for mounting mounting in a standard 19" rack, later called "R122")
* FM122 (frame mount, vertical orientation, for use in the [[014-002]] mounting frame, later called "F122")
* FM122 (frame mount, vertical orientation, for use in the [[014-002]] mounting frame, later called "F122")
==Manuals==
* [http://bama.edebris.com/download/tek/122_125/Tek%20122_125.pdf Tektronix 122 and 125 Manual]
* [http://w140.com/brophy_122_mod.pdf Low Noise Modifications of the 122 (PDF)]


==Pictures==
==Pictures==
<gallery>
<gallery>
Image:Tek 122 x.jpg|early model
Tek 122 x.jpg|early model
Image:Tek 122 x2.jpg|early model
Tek 122 x2.jpg|early model
Image:Tek 122 front.jpg|early model
Tek 122 front.jpg|early model
Image:Tek 122 power.jpg|early model
Tek 122 power.jpg|early model
Image:Tek 122 front close.jpg|early model
Tek 122 front close.jpg|early model
Image:Tek 122 bottom inside.jpg|early model
Tek 122 bottom inside.jpg|early model
Image:Tek 122 top inside.jpg|early model
Tek 122 top inside.jpg|early model
Image:Tek 122 schem.png
Tek 122 schem.png | schematic
Image:Tek 122 int right.jpg|late model
Tek 122 int right.jpg|late model
Image:Tek 122 int panel.jpg|late model
Tek 122 int panel.jpg|late model
Image:Tek 122 late int left.jpg|late model
Tek 122 late int left.jpg|late model
Image:Tek 122 late front.jpg|late model
Tek 122 late front.jpg|late model
Image:Tek 122 system rs 1.jpg
Tek 122 system rs 1.jpg
Image:Tek 122 system rs 2.jpg
Tek 122 system rs 2.jpg
Tek fm122 front.jpg|Tek FM122 front
Tek fm122 top connector.jpg|Tek FM122 top power connector
</gallery>
</gallery>


[[Category:Introduced in 1950]]
==Components==
{{Parts|122}}
 
[[Category:Amplifiers]]
[[Category:Amplifiers]]
Retrieved from "https://w140.com/tekwiki/wiki/Special:MobileDiff/19769...85391"