7A18: Difference between revisions
m (→Repair issues) |
No edit summary |
||
(24 intermediate revisions by 5 users not shown) | |||
Line 1: | Line 1: | ||
{{Plugin Sidebar | {{Plugin Sidebar | | ||
manufacturer=Tektronix | type=7A18| | |||
summary=75 MHz dual channel amplifier| | summary=75 MHz dual channel amplifier| | ||
image=Tek-7a18a-front.jpg | | image=Tek-7a18a-front.jpg | | ||
Line 6: | Line 6: | ||
introduced=1971 | | introduced=1971 | | ||
discontinued=1992 | | discontinued=1992 | | ||
series= | series=7000-series scopes| | ||
designers=Tom Rousseau| | |||
manuals= | manuals= | ||
* [ | * [[Media:070-1126-01.pdf|Tektronix 7A18+7A18N Instruction Manual]] (OCR) | ||
* [ | * [[Media:070-4329-00.pdf|Tektronix 7A18A Instruction Manual]] (OCR) | ||
* [http:// | <small> | ||
* [http:// | '''Alternates''' | ||
* [http://bama.edebris.com/download/tek/7a18/Tektronix_7A18_Service_June1974.pdf Tektronix 7A18 Manual] @ BAMA | |||
* [http://bama.edebris.com/download/tek/7a18a/tek-7a18a.pdf Tektronix 7A18A Manual] @ BAMA | |||
</small> | |||
}} | }} | ||
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 [[7000 series readout system|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 '''7A18A''' is mostly identical to the 7A18 predecessor, but replaces the custom low inductance potentiometers for gain and variable gain setting with a FET attenuator and regular potentiometers. | |||
The 7A18(A) uses a discrete front-end followed by [[M036|M36]] channel switch ICs for the vertical and trigger signals. | |||
The 200 MHz [[7A26]] and 400 MHz [[7A24]] share the same front panel layout and operation. | The 200 MHz [[7A26]] and 400 MHz [[7A24]] share the same front panel layout and operation. | ||
Line 33: | Line 42: | ||
{{Spec | Weight | 1.4 kg }} | {{Spec | Weight | 1.4 kg }} | ||
{{EndSpecs}} | {{EndSpecs}} | ||
==Links== | |||
* [https://www.youtube.com/watch?v=JZ76egcWH_4 Tektronix 7A18 II Repair and Alignment (With a Deeper Look at the High Frequency Compensation)] @ Zenwizard Studios YouTube | |||
* [https://youtu.be/Cz9kxXKlWUw Tektronix 7A18 Repair and Function Generator Alignment] @ Zenwizard Studios YouTube | |||
{{Documents|Link=7A18}} | |||
==Prices== | ==Prices== | ||
Line 44: | Line 58: | ||
! 1990 | ! 1990 | ||
|- | |- | ||
! Catalog | ! Catalog Price | ||
|align=right| $535 | |align=right| $535 | ||
|align=right| $615 | |align=right| $615 | ||
Line 51: | Line 65: | ||
|align=right| $1,790 | |align=right| $1,790 | ||
|- | |- | ||
! | ! In 2023 Dollars | ||
|align=right| $ | |align=right| $4,100 | ||
|align=right| $ | |align=right| $3,300 | ||
|align=right| $ | |align=right| $3,400 | ||
|align=right| $3, | |align=right| $3,700 | ||
|align=right| $ | |align=right| $4,200 | ||
|- | |- | ||
|} | |} | ||
==Repair issues== | ==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. | 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. | 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. | ||
===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== | ==Pictures== | ||
<gallery> | <gallery> | ||
Tek_7a18.jpg | Tek_7a18.jpg | 7A18 Front | ||
7a18-attenuator.jpg | 7A18 attenuator opened. One of the attenuation R/C modules has been unplugged to reveal the switch contacts. | |||
Tek 7A18 attenuator bottom.jpg | 7A18 attenuator, bottom (switch) side | |||
Tek-7603-front.jpg | A [[7603]] with two 7A18s | |||
Tek 7a17 7a18 7b50a model3 cart.jpg | 7A18 in [[7613]] mainframe | |||
7A18 and 7A18N from 070-1126-01.png | 7A18 and 7A18N from service manual 070-1126-01 | |||
Tek 7a18n.jpeg | 7A18N with "Identify" seen on an auction site - probably cobbled parts | |||
7A18N front.jpg | 7A18N Front | |||
7A18N RHS.jpg | 7A18N RHS switch cover removed | |||
7A18N LHS.jpg | 7A18N LHS switch cover removed | |||
7A18 R237A and B broken bond.jpg | Broken bond between ganged gain pots | |||
7A18N split ganged gain epoxy bond split zoom.png | Broken bond between ganged gain pots zoomed | |||
7A18 intact epoxy bond between ganged gain pots.jpg | Intact epoxy between ganged gain pots | |||
</gallery> | |||
===Development Prototypes=== | |||
<gallery> | |||
Tek 7a18 first prototype 1.jpg | First prototype of 7A18 | |||
Tek 7a18 first prototype 2.jpg | First prototype of 7A18 | |||
Tek 7a18 second prototype 1.jpg | Second prototype of 7A18 | |||
Tek 7a18 second prototype 2.jpg | Second prototype of 7A18 | |||
Third prototype of 7a18 1.jpg | Third prototype of 7A18 | |||
Third prototype of 7a18 2.jpg | Third prototype of 7A18 | |||
Third prototype of 7a18 3.jpg | Third prototype of 7A18 | |||
</gallery> | |||
===7A18A=== | |||
<gallery> | |||
Tek-7a18a-front.jpg | 7A18A Front | Tek-7a18a-front.jpg | 7A18A Front | ||
7a18a-left.jpg | 7A18A left side. The step attenuators can be seen on the left, the amplifier board on the right. | 7a18a-left.jpg | 7A18A left side. The step attenuators can be seen on the left, the amplifier board on the right. | ||
7a18a-right.jpg | 7A18A right side. The circuit boards on top carry the readout circuitry. | 7a18a-right.jpg | 7A18A right side. The circuit boards on top carry the readout circuitry. | ||
</gallery> | </gallery> | ||
'''Option 06''' | |||
<gallery> | <gallery> | ||
Tek-7a18a-opt06-front.jpg | 7A18A Opt.06 Front. AC/GND/DC switches have an extra rightmost "DC Offset" position enabling the offset controls. | Tek-7a18a-opt06-front.jpg | 7A18A Opt.06 Front. AC/GND/DC switches have an extra rightmost "DC Offset" position enabling the offset controls. | ||
Line 83: | Line 123: | ||
Tek-7a18a-opt06-offset.jpg | 7A18A Opt.06 - offset controls take the place of the Identify buttons on the standard model. | Tek-7a18a-opt06-offset.jpg | 7A18A Opt.06 - offset controls take the place of the Identify buttons on the standard model. | ||
</gallery> | </gallery> | ||
==Components== | |||
{{Parts|7A18}} | |||
{{Parts|7A18A}} | |||
[[Category:7000 series vertical plugins]] | [[Category:7000 series vertical plugins]] |
Latest revision as of 05:22, 8 January 2024
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 7A18A is mostly identical to the 7A18 predecessor, but replaces the custom low inductance potentiometers for gain and variable gain setting with a FET attenuator and regular potentiometers.
The 7A18(A) uses a discrete front-end followed by M36 channel switch ICs for the vertical and trigger signals.
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 |
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 |
---|---|---|---|---|---|
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
-
Broken bond between ganged gain pots zoomed
-
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 |