W
The Tektronix Type W is a differential comparator plug-in amplifier for 500-series scopes, designed by John Horn.
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/cm; 8 MHz @ 1 mV/cm |
| 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) |
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.
Links
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 | 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 | 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 |
Calibration Fixture
- 067-0503-00 Precision DC Divider, 10x & 100x
Operation
Type W has two signal inputs, "A" and "B", and a built in precision variable voltage supply, "VC", 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−VC, A−B, or VC−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 VC 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 12V version of the 6DJ8.
Pictures
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Front View
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Right View
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Left View
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Top View
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Bottom View
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Block Diagram
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Front view.
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Top-left view.
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Bottom view.
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Differential Comparator, initial version
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Input Attenuators
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Switching Diagram
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A-phase (prototype) Type W
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A-phase (prototype) Type W
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A-phase (prototype) Type W
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A-phase (prototype) Type W
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A-phase (prototype) Type W
