422

Tektronix 422

15 MHz portable dual-trace scope

Produced from 1965 to 1975

Manuals

(All manuals in PDF format and OCRed unless noted otherwise)

Manuals – Specifications – Links – Pictures

The Tektronix Type 422 is a 15 MHz portable dual-trace oscilloscope introduced in 1966. There was also a rack-mount version, the R422.

The 422's power supply is designed to be detachable, with a 24-pin Amphenol Micro Ribbon connector (same as later used for GPIB) used for the interconnect. The PSU side connector is fixed, the indicator unit side is at the end of a short cable and can be detached to operate with the PSU separated for maintenance.

Two PSU models were available, an AC-only version (016-0072-00) with a traditional line-frequency transformer, and an AC/DC version (016-0073-00) that can also charge an optional internal battery pack for operation without mains power. The AC/DC PSU is probably the earliest implementation of a switch-mode PSU in Tektronix equipment, albeit not operated directly off the AC line.

Key Specifications

Bandwidth	DC to 15 MHz
Risetime	< 23 ns
Sweep	500 ns/div to 0.5 s/div
Delay line	150 ns
Inputs	1 MΩ ±2% // 30 pF, max. 300 V DC+peak AC
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
Power	AC PS, 110/115/125 or 210/230/250 V_AC ±10%, 45 Hz to 440 Hz, 40 W; AC-DC PS, 92–137 or 184–274 V_AC, 45 Hz to 440 Hz, or 11.5–35 V DC, 30 W
Dimensions	AC PS 6.75"×10.0"×17.8", AC-DC PS 6.75"×10.0"×20.7" (H×W×D)

Links

Documents Referencing 422

Document	Class	Title	Authors	Year	Links
Tek 422 lecture notes.pdf	Article	Type 422 Lecture Notes	Chuck Miller	1965	422
Tekscope 1969 V1 N4 Aug 1969.pdf	Article	Nickel-Cadmium Battery Review		1969	321A • 323 • 410 • 422

Internals

Early versions use an 8056 Nuvistor tube for the front-end cathode follower, later versions use a FET. The 8056 Nuvistor can be replaced directly by a MPF102 JFET plugged into its socket.

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, Tektronix' first CRT with a scan expansion mesh, which allowed a four-inch diagonal screen size in a package depth comparable to the 300 series. The HV supply to the CRT is from a single 700 V_p-p winding with two multiplier circuits using semiconductor diodes, a ×7 multiplier producing +4.9 kV, and a ×3 multiplier producing –2.1 kV that feeds a regulator based on a GV4S-1400 "Corotron" HV regulator tube to set the grid potential at –1.4 kV. The tube has dedicated blanking electrodes (pins 7, 12).

Pictures

External

Rear face of 422 without DC battery option
R422, compartment closed
R422, compartment open
Black 422, panel mount
422 trace is sharp
422 in ALT
AC Power Cord with UK Plug
DC Power Cord
422 MOD 246D for Burroughs

Internal

Tek 422 Internal LHS
Tek 422 Internal RHS
Tek 422 Internal Top
Tek 422 Internal Rear
Tek 422 Internal Underside
Tek 422 Internal V-Amp
Tek 422 H-Amp Board
Tek 422 Trigger Board
Tek 422 Input Board#1
Tek 422 Input Board#1
Tek 422 Indicator unit - Regulator
Tek 422 HV Case
MPF102 replacing 8056
Tek422 AC Power Supply Module
Tek 422 AC Power supply Internal
Tek 422 AC Power supply Internal
Tek 422 AC Power supply Internal
Tek 422 AC Power supply Internal
Tek 422 AC Power supply Internal
Tek 422 Indicator unit, Power supply Test points

Schematic

Trigger circuit
Sweep circuit
Vertical amplifier circuit
Input amplifier circuit
Horizontal amplifier circuit
CRT circuit
ac-dc power supply
ac power supply

Components

Some Parts Used in the 422

Part	Part Number(s)	Class	Description	Used in
1N3713	152-0125-00	Discrete component	1 mA, 5 pF germanium tunnel diode	422
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
8393	154-0461-00	Vacuum Tube (Triode)	Nuvistor triode	422 • 453 • 454 • 1A6 • 1A7 • 503
GV4S-1400	154-0432-00	Gas Discharge Tube (Voltage regulator)	"Corotron" high-voltage regulator tube	422
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

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