W

Tektronix Type W

8-23 MHz differential comparator

Compatible with 500-series scopes

Produced from 1965 to 1974

Manuals

(Manuals are OCRed PDF files unless noted otherwise)

Manuals – Specifications – Links – Pictures

The Tektronix Type W is a differential comparator plug-in amplifier for 500-series scopes, designed by John Horn.

Type W is faster (bandwidth 23 MHz to 8 MHz depending on gain) than its Type Z predecessor, and it extends performance in terms of sensitivity, reaching 1 mV/div. It achieves 20,000 to 1 common-mode rejection at DC and low frequencies.

Key Specifications

Deflection	1 mV/div to 50 V/div, 1–2–5 (6-position) and 4-position decade attenuator
Input impedance	1 MΩ // 20 pF (either input)
Bandwidth	26 MHz (23 MHz below S/N 7000) @ 50 mV/div; 8 MHz @ 1 mV/div
Common Mode Range	±15 V after INPUT ATTEN
CMRR	DC Coupled: 20000:1 DC to 20 kHz, 500:1 at 500 kHz; AC Coupled: 1000:1 at 60 Hz
Signal ranges

Maximum Input Voltage (S/N 7000-up)
DC Coupled	350 V
AC Coupled	500 V
Maximum Input Voltage (S/N 101-6999)
INPUT ATTEN = 1	15 V
INPUT ATTEN = 10	150 V
INPUT ATTEN = 100	±350 V (DC Coupled); 500 V (AC Coupled)
INPUT ATTEN = 1000	±350 V (DC Coupled); 500 V (AC Coupled)

Links

067-0503-00 Calibration Fixture – Precision DC Divider, 10× and 100×

Documents referencing W

Document	Class	Title	Authors	Year	Links
Tekscope 1970 V2 N5 Oct 1970.pdf	Article	Amplitude Measurement to Better Than 1%		1970	1S1 • 7503 • 7A13 • 1A5 • W • 3A7
Tekscope 1972 V4 N5 Sep 1972.pdf	Article	A Practical Approach to Differential Amplifiers and Measurements (Part 1)	Fred Beckett	1972	112 • 11A33 • 1A5 • 1A6 • 1A7 • 1A7A • 26A2 • 3A9 • 5A22N • 7A13 • 7A22 • AM502 • D • E • G • P6055 • P6046 • W • Z
Tekscope 1972 V4 N6 Nov 1972.pdf	Article	A Practical Approach to Differential Amplifiers and Measurements (Part 2)	Fred Beckett	1972	112 • 11A33 • 1A5 • 1A6 • 1A7 • 1A7A • 26A2 • 3A9 • 5A22N • 7A13 • 7A22 • AM502 • D • E • G • P6055 • P6046 • W • Z

Operation

Type W has two signal inputs, "A" and "B", and a built in precision variable voltage supply, "V_C", which is controlled by a ten-turn pot and can vary from either −1.1 V to +1.1 V or −11 V to +11 V. A mode switch selects between displaying A−V_C, A−B, or V_C−B. The "A−B" mode is particularly useful for displaying the current in a sense resistor, while the other modes provide "slideback" measurements of small variations superimposed on a large constant. An output of V_C is provided on the front panel for precision measurements.

Unlike the Type Z, Type W has two gain axes: a decade attenuator and a 1−2−5−10−20−50 selector, reminiscent of Type D from ten years before.

Type W is the only letter-series plug-in with an "infinite resistance" input mode selectable at the front panel. (Types 1A5 and 1A7 have an internal jumper that can be cut.)

Early production Type W in a 556 mainframe won't meet spec for overdrive recovery time, because an overdriven W passes enough common-mode to the mainframe vertical amp to saturate it. At S/N 3270, this was fixed, by adding another stage to attenuate CM. The new "output amp" circuit board clips onto the rear bulkhead; significant hand mods are required on the chassis. This was also offered as Modification kit 040-0447-00 to retrofit existing instruments.

Type W was created with a pair of type 8056 Nuvistors in the front end. In 1971 (S/N 7000), following the lead of Type 1A7, the Nuvistors were replaced by JFETs to reduce drift. Mod kit 040-0590-00 was offered for existing instruments.

In the letter-series timeline of differential comparators, Type W, introduced in 1965, follows Type Z and precedes Type 1A5.

Type W uses three type 8416 tubes, the 12 V version of the 6DJ8.

Pictures

Front View
Right View
Left View
Top View
Bottom View
Block Diagram
Front view.
Top-left view.
Bottom view.
Differential Comparator, initial version
Input Attenuators
Switching Diagram
A-phase (prototype) Type W
A-phase (prototype) Type W
A-phase (prototype) Type W
A-phase (prototype) Type W
A-phase (prototype) Type W

Components

Some Parts Used in the W

Part	Part Number(s)	Class	Description	Used in
8056	154-0417-00	Vacuum Tube (Triode)	low-voltage Nuvistor triode	422 • 502 • W • 1S1 • 3A7 • 3S3 • 3T4 • 5T3 • 10A1
8416	154-0413-00 • 157-0116-00	Vacuum Tube (Dual Triode)	dual triode	1S1 • 2A61 • 3A8 • 3L5 • W

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