112
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 |
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| 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
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1955 Catalog photo
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Manual photo
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Main schematic
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Power Supply Schematic
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Calibrator Schematic
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Bottom deck. Fan is missing; fan yoke still present.
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Underside of bottom deck, front.
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Underside of bottom deck, rear.
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Underside of top deck.
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Vibration-isolated front-end amplifier
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Deflection sensitivity switch.
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Top internal
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Top front internal
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Top rear internal
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Rear of front panel has sockets for holding spare tubes.
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Tek 112 ad from Electronics, Dec 1949
Components
Some Parts Used in the 112
| Part | Part Number(s) | Class | Description | Used in |
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| 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 |