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Tektronix 190
Constant-Amplitude Signal Generator
Tek 190B front

Produced from 1954 to (?)

Manuals – Specifications – Links – Pictures

The Tektronix Type 190A and 190B Constant-Amplitude Signal Generator is a sine wave source that uses feedback to provide a signal whose amplitude does not vary with frequency or with the impedance of the load, within stated limits.

The frequency range is 350 kHz to 50 MHz. The amplitude measurement is made using a peak-to-peak (envelope) detector in an external attenuator head that is connected to the main unit by a special cable. The 190A uses a 6110 double diode tube for the detector. The 190B uses two 1N87A germanium diodes for the detector.

The 190 is useful for measuring the frequency response of a device whose input impedance varies with frequency. If a standard 50-ohm signal generator is used for this purpose, the frequency-domain variations of the input impedance of the device under test will result in frequency-domain variations in the actual signal voltage that is applied to the input. This interaction between is input impedance and gain measurements is often undesirable. Having a constant-amplitude source simplifies the measurement.

The oscillation frequency of the 190B is controlled by a rotary variable capacitor. The variable capacitor rotates together with a drum that serves as the frequency readout dial. The drum is made of cream colored plastic and has a diameter of 5" (12.5 cm) and a height of 4" (10 cm). The frequency knob on the front panel of the 190B turns a rubber wheel which, by friction, turns the drum. The relatively large diameter of the drum provides for precise frequency control, long effective length of the readout dial, and ensures that the friction coupling between the frequency knob and the drum provides sufficient torque to turn the drum and rotary capacitor without any slippage.

The 067-0041-00 modification kit extends the low-frequency range of the 190A.


Some Parts Used in the 190

Page Class Description Used in
12AU7 Vacuum Tube (Dual Triode) dual medium-μ triode 122 160 161 162 181 190 310 316 317 502 502A 512 516 517 517A 526 535 536 545 545A 545B 547 549 555 575 581 581A 585 585A C D E N Q
5Y3 Vacuum Tube (Diode) rectifier 190
6110 Vacuum Tube (Dual Diode) small-signal dual diode 190
6AL5 Vacuum Tube (Dual Diode) high-perveance dual diode 163 181 190 310 310A 315 316 317 502 502A 503 511 511A 512 516 517 517A 526 535 535A 545 545A 549 581 581A 585 585A 551 C T Telequipment S52
6AU6 Vacuum Tube (Pentode) RF pentode 2A60 80 107 160 181 190 310 310A 316 317 360 502 502A 512 513 516 517 517A 526 529 RM529 531 531A 535 536 545 545A 546 547 549 555 575 581 581A 585 585A C CA Q
6C4 Vacuum Tube (Triode) VHF triode 190 517 517A