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The Tektronix 112 is a DC-coupled differential amplifier [[introduced in 1955]].
{{Instrument Sidebar
The voltage gain can be set from 0.5 to 5000 V/V. 
|manufacturer=Tektronix
The frequency response is DC to 2MHz when the gain is set
|model=112
below 166, and DC to 1MHz for gain settings greater than that.
|class=Amplifier
The 121 is intended for use with the
|series=
[[511]], [[512]], [[514]], and [[524]] oscilloscopes.
|summary=Differential amplifier
The input impedance is 1 megohm in parallel with 47 pF.
|image=Tek 112 front.jpg
The output impedance is 8000 ohms.  The amplifier's
|caption=Tek 112 front
response is identical to that of a Tek 512.
|introduced=1949
|discontinued=(?)
|designers=
|manuals=
* [[Media:070-053.pdf|Tektronix 112 Manual]]
}}
The '''Tektronix 112''' is a DC-coupled differential amplifier [[introduced in 1949]].


* [http://w140.com/tek_112.pdf Tektronix 112 Manual (PDF)]
The 112 is intended for use with the [[511]], [[512]], [[514]], and [[524]] oscilloscopes.


Photos needed.
{{BeginSpecs}}
{{Spec | Amplification    | 0.5 to 5000 V/V }}
{{Spec | Bandwidth        | DC to 2 MHz @ gain < 166; DC to 1 MHz above }}
{{Spec | Input impedance  | 1 MΩ // 47 pF }}
{{Spec | Output impedance | 8 kΩ }}
{{EndSpecs}}


==Internals==
The amplifier's schematic and response are identical to that of a [[512|Tek 512]].
The first stage is a differential amplifier using a pair of [[5879]] pentodes. 
Next is a differential amplifier using a pair of [[12AU6]] pentodes. 
The 112 has a differential output intended for directly driving the vertical deflection plates of a CRT.
The output terminals of the 112 are on the right side in the rear, so the 112 can sit to the left of an oscilloscope and short wires can connect the 112 to the oscilloscope's CRT.
A two-position switch on the rear panel of the Type 112 controls the common-mode output voltage.
In one position, the common-mode output voltage is +150 V, which is the plate voltage of the [[6AG7]] tubes of the output amplifier.
In the other position, the common-mode output voltage is 0 V.
The shifting of the common-mode output voltage 150 V downward is accomplished by enabling a pair of 680 μA DC current sinks that cause a voltage drop on 220 kΩ series output resistors.
[[6CB6]] pentodes form the current sinks, with their cathodes tied to -150 V.
The 220 kΩ output resistors also provide short circuit protection.
The Type 112 manual recommends 0 V for driving the CRT of the [[511]], and +150 V for driving the CRT of the [[512]], [[513]], or [[514]].
==See Also==
* [[121]]
==Prices==
* 1949: $495  (~ $6,300 in 2023 dollars)
==Pictures==
<gallery>
<gallery>
Image:Tek 112.jpg|1955 Catalog photo
tek_112_18.jpg
Image:Tek 112 front.jpg|Manual photo
Tek 112.jpg|1955 Catalog photo
Tek 112 front.jpg|Manual photo
Tek 112 main schematic.png|Main schematic
Tek_112.power_supply.png|Power Supply Schematic
Tek 112 calibrator schematic.png|Calibrator Schematic
tek_112_10.jpg|Bottom deck. Fan is missing; fan yoke still present.
tek_112_11.jpg
tek_112_13.jpg|Underside of bottom deck, front.
tek_112_14.jpg|Underside of bottom deck, rear.
tek_112_15.jpg|Underside of top deck.
tek_112_16.jpg|Vibration-isolated front-end amplifier
tek_112_20.jpg|Deflection sensitivity switch.
tek_112_3.jpg|Top internal
tek_112_4.jpg|Top front internal
tek_112_5.jpg|Top rear internal
tek_112_6.jpg
tek_112_7.jpg
tek_112_8.jpg|Left rear. Power supply tubes on the left: three [[5V4G]] rectifiers (one missing) and one [[6AS7]] triode series pass tube.
tek_112_9.jpg|Rear of front panel has sockets for holding spare tubes.
tek_112_2.jpg
tek_112_1.jpg
Tek 112 ad - Electronics-1949-12.jpg | Tek 112 ad from Electronics, Dec 1949
</gallery>
</gallery>
==Components==
{{Parts|112}}
[[Category:Differential amplifiers]]

Latest revision as of 11:39, 9 February 2024

Tektronix 112
Differential amplifier
Tek 112 front

Produced from 1949 to (?)

Manuals
(All manuals in PDF format unless noted otherwise)
Manuals – Specifications – Links – Pictures

The Tektronix 112 is a DC-coupled differential amplifier introduced in 1949.

The 112 is intended for use with the 511, 512, 514, and 524 oscilloscopes.

Key Specifications

Amplification 0.5 to 5000 V/V
Bandwidth DC to 2 MHz @ gain < 166; DC to 1 MHz above
Input impedance 1 MΩ // 47 pF
Output impedance 8 kΩ

Internals

The amplifier's schematic and response are identical to that of a Tek 512.

The first stage is a differential amplifier using a pair of 5879 pentodes. Next is a differential amplifier using a pair of 12AU6 pentodes.

The 112 has a differential output intended for directly driving the vertical deflection plates of a CRT. The output terminals of the 112 are on the right side in the rear, so the 112 can sit to the left of an oscilloscope and short wires can connect the 112 to the oscilloscope's CRT.

A two-position switch on the rear panel of the Type 112 controls the common-mode output voltage. In one position, the common-mode output voltage is +150 V, which is the plate voltage of the 6AG7 tubes of the output amplifier. In the other position, the common-mode output voltage is 0 V.

The shifting of the common-mode output voltage 150 V downward is accomplished by enabling a pair of 680 μA DC current sinks that cause a voltage drop on 220 kΩ series output resistors. 6CB6 pentodes form the current sinks, with their cathodes tied to -150 V. The 220 kΩ output resistors also provide short circuit protection.

The Type 112 manual recommends 0 V for driving the CRT of the 511, and +150 V for driving the CRT of the 512, 513, or 514.

See Also

Prices

  • 1949: $495 (~ $6,300 in 2023 dollars)

Pictures

  • 1955 Catalog photo

    1955 Catalog photo

  • Manual photo

    Manual photo

  • Main schematic

    Main schematic

  • Power Supply Schematic

    Power Supply Schematic

  • Calibrator Schematic

    Calibrator Schematic

  • Bottom deck. Fan is missing; fan yoke still present.

    Bottom deck. Fan is missing; fan yoke still present.

  • Underside of bottom deck, front.

    Underside of bottom deck, front.

  • Underside of bottom deck, rear.

    Underside of bottom deck, rear.

  • Underside of top deck.

    Underside of top deck.

  • Vibration-isolated front-end amplifier

    Vibration-isolated front-end amplifier

  • Deflection sensitivity switch.

    Deflection sensitivity switch.

  • Top internal

    Top internal

  • Top front internal

    Top front internal

  • Top rear internal

    Top rear internal

  • Left rear. Power supply tubes on the left: three 5V4G rectifiers (one missing) and one 6AS7 triode series pass tube.

    Left rear. Power supply tubes on the left: three 5V4G rectifiers (one missing) and one 6AS7 triode series pass tube.

  • Rear of front panel has sockets for holding spare tubes.

    Rear of front panel has sockets for holding spare tubes.

  • Tek 112 ad from Electronics, Dec 1949

    Tek 112 ad from Electronics, Dec 1949

Components

Some Parts Used in the 112

Part Part Number(s) Class Description Used in
12AU6 154-0040-00 Vacuum Tube (Pentode) RF pentode 81 • 112 • 1L10 • 1L20 • 1L60 • 3L10 • 512 • 556 • 575 • 545 • 547 • 549 • 581 • 585 • A • B • C • G • K • H • L • ML • M • N • O • R • S • Z
5879 154-0055-00 Vacuum Tube (Pentode) sharp-cutoff pentode 112 • 512 • D • E • Hickok 1825
6AG7 154-012 • 154-0012-00 Vacuum Tube (Pentode) 9 Watt power pentode 104 • 104A • 105 • 112 • 511 • 511A • 512 • 513 • 514 • 517 • 517A • 524
6CB6A 154-0030-00 Vacuum Tube (Pentode) pentode 105 • 112 • 316 • 317 • 503 • 504 • 513 • 517 • 517A • 541 • 535 • 545 • 63 • 2A63
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