422

Manuals – Specifications – Links – Pictures

The Tektronix Type 422 is a 15 MHz portable dual-trace oscilloscope introduced in 1966. It was available with an optional battery back for operation without mains power.

Key Specifications

Bandwidth	DC to 15 MHz
Risetime	< 23 ns
Sweep	500 ns/div to 0.5 s/div
Input impedance	1 MΩ ±2% // 30 pF
Delay line	150 ns, internal delay line
Input voltage	Max. 300 V combined DC and peak AC
Trigger source	CH1 & CH2, CH1, External
Channel isolation	100:1 at 40 KHz
Calibrator	~1 kHz ±20%, 2 V ext jack, 0.2 V internal, square wave
CRT	T4220 tube, P31 phosphor, 6 kV acceleration (Post-def 4.9 kV), 8 × 10  graticule, 0.8 cm/div
Operating temperature	–15 °C to +55 °C
Power	AC PS, 110/115/125 or 210/230/250 VAC ±10%, 45 Hz to 440 Hz, 40 W AC-DC PS, 92–137 or 184–274 VAC, 45 Hz to 440 Hz, 11.5–35 V DC, 30 W
Dimensions	AC PS (H/W/D) 6.75/10.0/17.8 inches, AC-DC PS (H/W/D) 6.75/10.0/20.7 inches

Internals

Early versions use an 8056 Nuvistor tube for the front-end cathode follower. Later versions use a FET front end. The 8056 Nuvistor used in the input amplifier of the 422 can be replaced by a MPF102 JFET.

The trigger circuit in the 422 has a trigger amplifier driving a 1N3719 tunnel diode, D375, which acts as a Schmitt trigger. The trigger amplifier has a nonlinear deadband diode circuit in the negative feedback path. What results is high gain for small signals (little or no negative feedback) and low gain for large signals (strong negative feedback). Thus, the signal at the base of Q364 has a limited swing over a wide range of input amplitudes. The collector current of Q364 varies between 0 and 9 mA. Depending on the position of the trigger slope control, higher collector current in Q364 either switches D375 from the low-voltage state to the high-voltage state or from the high-voltage state to the low-voltage state. When D375 transitions from the low-voltage state to the high-voltage state, it produces a current pulse in the primary of transformer T401, which produces a current pulse in the secondary of T401. The secondary of T401 feeds another tunnel diode, D405, and the current pulse switches D405 to the high-voltage state, which starts a sweep.

The 422 uses the T4220 CRT.

Links

• LazyElectrons Video on 422

Pictures

External

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  R422, compartment closed

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  R422, compartment open

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  Black 422, panel mount

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  422 trace is sharp

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  422 in ALT

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  AC Power Cord with UK Plug

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  DC Power Cord

Internal

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  Tek 422 Internal LHS

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  Tek 422 Internal RHS

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  Tek 422 Internal Top

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  Tek 422 Internal Rear

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  Tek 422 Internal Underside

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  Tek 422 Internal V-Amp

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  Tek 422 H-Amp Board

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  Tek 422 Trigger Board

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  Tek 422 Input Board#1

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  Tek 422 Input Board#1

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  Tek 422 Indicator unit - Regulator

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  Tek 422 HV Case

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  MPF102 replacing 8056

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  Tek422 AC Power Supply Module

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  Tek 422 AC Power supply Internal

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  Tek 422 AC Power supply Internal

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  Tek 422 AC Power supply Internal

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  Tek 422 AC Power supply Internal

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  Tek 422 AC Power supply Internal

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  Tek 422 Indicator unit, Power supply Test points

Schematic

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  Trigger circuit

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  Sweep circuit

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  Vertical amplifier circuit

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  Input amplifier circuit

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  Horizontal amplifier circuit

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  CRT circuit

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  ac-dc power supply

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  ac power supply

Some Parts Used in the 422

Part	Part Number(s)	Class	Description	Used in
1N3714	152-0081-00	Discrete component	2.2 mA, 25 pF germanium tunnel diode	546 • 547 • 556 • 21A • 22A • 3B1 • 3B2 • 3B3 • 422 • 491 • 283
1N3719	152-0182-00	Discrete component	10 mA, 50 pF germanium tunnel diode	422 • 661 • 7B92 • 7B92A
8056	154-0417-00	Vacuum Tube (Triode)	low-voltage Nuvistor triode	422 • 502 • W • 1S1 • 3A7 • 3S3 • 3T4 • 5T3 • 10A1
STD933	152-0181-00	Discrete component	1 mA, 5 pF germanium tunnel diode	1S2 • 221 • 422
T4220	154-0466-00 • 154-0466-05	CRT	rectangular 3⅜ × 3⅞ flat-faced CRT	422
TD714	152-0402-00	Discrete component	2.2 mA, 25 pF tunnel diode	1401 • 1401A • 283 • R283 • 3B2 • 3B3 • 422 • 491 • 546 • RM546 • 547 • RM547 • 556 • RM556 • SPG11 • SPG12
ZZ1000	154-370 • 154-0370-00	Gas Discharge Tube (Voltage regulator)	81 V voltage reference	129 • 3B1 • 3B1S • 3B2 • 3B3 • 3S76 • 422 • S-311