7854
The Tektronix 7854 Waveform Processing Oscilloscope, introduced in 1980, is a 400 MHz combined analog / digital mainframe in the 7000 series that takes two vertical and two horizontal 7000-series plug-ins. In addition to a conventional analog (real time) scope, it contains an equivalent-time sampling 10-bit digitizer and a programmable waveform processor with GPIB interface. Single-shot, pretrigger acquisition is possible with special 7B87 time base using real-time sampling. The project manager for the 7854 was Tom Rousseau.
The waveform processor can be programmed using a detachable calculator-style keyboard, using postfix operators ("reverse Polish notation" like HP calculators) that operate on entire waveforms, not just individual numbers.
Key Specifications
| Bandwidth | (analog) 400 MHz |
|---|---|
| Fastest cal. sweep | 500 ps |
| Sample rate | 500 kHz (stores repetitive waveforms up to 400 MHz) |
| Resolution | 10 bit |
| Acquisition depth | 128, 256, 512 or 1024 points |
| Memory capacity | 2048 waveform points in up to 16 waveforms (optional expansion to 5120 points and 40 waveforms) |
| Single shot | events and pretrigger up to 50 µs/div ("2.5 µs/point") with the 7B87 Time Base |
| CRT | 154-0644-05 (P-31) or 154-0893-09 (P-11); cathode −3 kV, anode +21 kV, distributed vertical deflection plates |
| Features |
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Internals
The acquisition system uses what Tektronix termed a "display-oriented random sampling digitizing technique". It simultaneously digitizes a pair of X and Y signal values at a rate of 3.5 µs/point, using Schottky diode bridge based sample/hold circuits and a single 10-bit successive-approximation ADC. The Y sample value is then written into the memory location addressed by the X value, using DMA.
The CPU in the 7854 is a Texas Instruments TMS9900 16-bit microprocessor, known from the infamous TI-99/4 home computer of the late 70s, with 32+6KByte ROM and 8KByte RAM.
The firmware consists of mask ROMs, an FPLA, and patch EPROMs. These ROMs (particularly the early ones from Mostek) are a common point-of-failure. Several remedies exist, outlined here.
Software
Prices
| Year | 1981 | 1990 |
|---|---|---|
| Catalog price | $10,500 | $17,000 |
| 2019 value | $29,360 | $33,060 |
Diagnostic Test Interfaces
- 067-0911-00 Diagnostic Test Interface
- 067-0912-00 Analog Test Card for 7854
- 067-0961-00 Diagnostic Memory Board
Extender Boards
- 067-0913-00 Extender Board 44-Pin (used with the A30-GPIB and A31-ROM Boards)
- 067-0914-00 Extender Board 80-Pin (used with the A27-MPU and A28-RAM Boards)
- 067-0915-00 Extender Board 124-Pin (used with the A26-Control Logic and A29-Display Boards)
Links
- Tek 7854 Design Team
- Tek 7854 @ amplifier.cd
- Tek 7854 @ barrytech.com
- Mostek ROM Repairs @ vintagetek.org
- overview of ROM repair options @ paulcarbone.com
Pictures
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7854 Rear
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7854 Rear with combined RAM and ROM boards
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Waveform Calculator Keyboard
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Waveform Calculator Keyboard
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Digital section in the 7854
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A2 Mode Switch
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A2 Mode Switch
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A7 Aux Reg
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A11 Main Interface
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A15 Signal Output
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A15 Signal Output
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A15 Signal Out Board
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A17 Horizontal Amp Board
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A18 Vertical Amp Board
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A19 Vertical Channel Switch
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A19 Vertical Channel Switch
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A20 High Voltage
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A21 Z-Axis
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A25 Digitizer
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A26 Control Logic Board
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A26 Control Logic Board
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A27 MPU
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A28 RAM Board
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A28 RAM Board with option 2D (RAM Expansion)
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A29 Display Board
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A30 GPIB
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A31 ROM Board
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A32 Rear Panel Connector
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7854 Top
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7854 Left
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7854 Right
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7854 Rear
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7854 Rear with combined RAM and ROM boards
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Picture of 7854 during development. Note the different measurement keyboard layout. Picture might date from late 1978
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Picture of designing the 7854 waveform calculator keyboard. note the different Keyboard layout.
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Alignment Pattern
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Program for generating Alignment Pattern
