7A18
The Tektronix 7A18 is a general-purpose 75 MHz dual-trace vertical plug-in for 7000-series scopes. Model 7A18N is identical except it omits the readout circuits.
Option 06 (first offered in 1975 catalog) adds offset voltage controls giving ±200 Div offset range. This option replaces the IDENTIFY buttons with DC offset controls, and adds a fourth "DC offset" position to the input coupling switch.
The 200 MHz 7A26 and 400 MHz 7A24 share the same front panel layout and operation.
The 7A18 uses a discrete front-end followed by M36 channel switch ICs for the vertical and trigger signals.
Key Specifications
Input impedance | 1 MΩ // 20 pF |
---|---|
Deflection | 5 mV/div to 5 V/div in 1–2–5 sequence, 2% |
Bandwidth | 0 – 75 MHz (DC), 10 Hz – 75 MHz (AC) |
Noise | < 300 μV in 5 mV/Div |
Option 06 offset range | ±200 Div equiv. from ±1 V in 5 mV/Div range up to ±200 V in 1 V/Div range (above that limited by maximum input voltage) |
Features |
|
Weight | 1.4 kg |
Links
- Tektronix 7A18 II Repair and Alignment (With a Deeper Look at the High Frequency Compensation) @ Zenwizard Studios YouTube
- Tektronix 7A18 Repair and Function Generator Alignment @ Zenwizard Studios YouTube
Documents Referencing 7A18
Document | Class | Title | Authors | Year | Links |
---|---|---|---|---|---|
7000 series brochure March 1973.pdf | Brochure | 7000 series brochure, March 1973 | 1973 | 7A11 • 7A12 • 7A13 • 7A14 • 7A15A • 7A16A • 7A17 • 7A18 • 7A19 • 7A21N • 7A22 • 7B50 • 7B53A • 7B70 • 7B71 • 7B92 • 7CT1N • 7D11 • 7D13 • 7D14 • 7D15 • 7M11 • 7L12 • 7S11 • 7S12 • 7T11 • 7704A • R7704 • 7904 • R7903 • 7603 • R7603 • 7403N • R7403N • 7313 • R7313 • 7613 • R7613 • 7623 • R7623 • P7001 | |
Tekscope 1977 V9 N1.pdf | Article | Counter and Oscilloscope Combination Makes Difficult Measurements | Emory Harry | 1977 | DC505A • 7B53A • 7A18 • 7603 |
Prices
Year | 1971 | 1976 | 1980 | 1984 | 1990 |
---|---|---|---|---|---|
Catalog Price | $535 | $615 | $915 | $1,250 | $1,790 |
In 2023 Dollars | $4,100 | $3,300 | $3,400 | $3,700 | $4,200 |
Repair issues
Attenuator solder joints
The pins of the attenuator modules are connected to conductive traces on the ceramic substrate inside by low-temperature soldering, which can go bad. Re-seating the module can temporarily restore the internal contact but will usually not fix the problem permanently. Repair is possible by opening the click-locked lid and carefully resoldering.
Variable gain pots
These pots (R237A,B and R437A,B 315-0241-00) are bonded together - that bond can break which stops the gain push from working. Looking at a few 7A18s, I see that the design was changed at least once.
Pictures
-
7A18 Front
-
7A18 attenuator opened. One of the attenuation R/C modules has been unplugged to reveal the switch contacts.
-
7A18 attenuator, bottom (switch) side
-
A 7603 with two 7A18s
-
7A18 in 7613 mainframe
-
7A18 and 7A18N from service manual 070-1126-01
-
7A18N with "Identify" seen on an auction site - probably cobbled parts
-
7A18N Front
-
7A18N RHS switch cover removed
-
7A18N LHS switch cover removed
-
Broken bond between ganged gain pots
-
Intact epoxy between ganged gain pots
Development Prototypes
-
First prototype of 7A18
-
First prototype of 7A18
-
Second prototype of 7A18
-
Second prototype of 7A18
-
Third prototype of 7A18
-
Third prototype of 7A18
-
Third prototype of 7A18
7A18A
-
7A18A Front
-
7A18A left side. The step attenuators can be seen on the left, the amplifier board on the right.
-
7A18A right side. The circuit boards on top carry the readout circuitry.
Option 06
-
7A18A Opt.06 Front. AC/GND/DC switches have an extra rightmost "DC Offset" position enabling the offset controls.
-
7A18A Opt.06 left side (rear). Note the two blue 10T-potentiometers for offset voltage adjustment.
-
7A18A Opt.06 - offset controls take the place of the Identify buttons on the standard model.
Components
Some Parts Used in the 7A18
Part | Part Number(s) | Class | Description | Used in |
---|---|---|---|---|
155-0022-00 | 155-0022-00 • 155-0022-01 | Monolithic integrated circuit | analog multiplexer | 147 • 148 • 149 • 335 • 468 • 1430 • 1441 • 1461 • 1900 • 1910 • 2220 • 2221 • 2230 • 5223 • 5403 • 5440 • 5441 • 5443 • 5444 • 5A38 • 7313 • 7403N • 7503 • 7504 • 7514 • 7603 • AN/USM-281C • 7613 • 7623 • 7623A • 7633 • 7704 • R7704 • 7704A • 7834 • 7844 • 7854 • R7912 • 7912AD • 7912HB • 7904 • R7903 • 7904A • 7934 • 7A12 • 7A18 • 7A18A • 7A18N • 7B52 • 7B53N • 7D10 • 7D11 • 7D12 • NT-7000 • P7001 |
Some Parts Used in the 7A18A
Part | Part Number(s) | Class | Description | Used in |
---|---|---|---|---|
155-0022-00 | 155-0022-00 • 155-0022-01 | Monolithic integrated circuit | analog multiplexer | 147 • 148 • 149 • 335 • 468 • 1430 • 1441 • 1461 • 1900 • 1910 • 2220 • 2221 • 2230 • 5223 • 5403 • 5440 • 5441 • 5443 • 5444 • 5A38 • 7313 • 7403N • 7503 • 7504 • 7514 • 7603 • AN/USM-281C • 7613 • 7623 • 7623A • 7633 • 7704 • R7704 • 7704A • 7834 • 7844 • 7854 • R7912 • 7912AD • 7912HB • 7904 • R7903 • 7904A • 7934 • 7A12 • 7A18 • 7A18A • 7A18N • 7B52 • 7B53N • 7D10 • 7D11 • 7D12 • NT-7000 • P7001 |