7A18: Difference between revisions
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==Repair issues== | ==Repair issues== | ||
The pins of the attenuator modules are connected to | The pins of the attenuator modules are connected to conductive traces on a 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. | 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. | Repair is possible by opening the click-locked lid and carefully resoldering. | ||
Revision as of 12:48, 5 October 2020
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.
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 |
Prices
| Year | 1971 | 1976 | 1980 | 1984 | 1990 |
|---|---|---|---|---|---|
| Catalog price | $535 | $615 | $915 | $1,250 | $1,790 |
| 2018 value | $3,300 | $2,700 | $2,770 | $3,000 | $3,420 |
Repair issues
The pins of the attenuator modules are connected to conductive traces on a 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.
Pictures
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7A18 Front
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7A18A Front
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7A18A left side. The step attenuators can be seen on the left, the amplifier board on the right.
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7A18A right side. The circuit boards on top carry the readout circuitry.
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7A18 attenuator opened. One of the attenuation R/C modules has been unplugged to reveal the switch contacts.
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A 7603 with two 7A18s
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7A18 in 7613 mainframe
Option 06
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7A18A Opt.06 Front. AC/GND/DC switches have an extra rightmost "DC Offset" position enabling the offset controls.
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7A18A Opt.06 left side (rear). Note the two blue 10T-potentiometers for offset voltage adjustment.
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7A18A Opt.06 - offset controls take the place of the Identify buttons on the standard model.
