7A18: Difference between revisions

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{{Plugin Sidebar 2|
{{Plugin Sidebar |
title=Tektronix 7A18|
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=[[7000-series scopes]]|
series=7000-series scopes|
designers=Tom Rousseau|
manuals=
manuals=
* [http://bama.edebris.com/download/tek/7a18/Tektronix_7A18_Service_June1974.pdf Tektronix 7A18 Manual (PDF)]
* [[Media:070-1126-01.pdf|Tektronix 7A18+7A18N Instruction Manual]] (OCR)
* [http://bama.edebris.com/download/tek/7a18a/tek-7a18a.pdf Tektronix 7A18A Manual (PDF)]
* [[Media:070-4329-00.pdf|Tektronix 7A18A Instruction Manual]] (OCR)
* [http://w140.com/smb/7a18_7a18n_sm.pdf Tektronix 7A18+7A18N Manual (OCR, PDF)]
<small>
* [http://w140.com/smb/7a18a_sm.pdf Tektronix 7A18A Manual (OCR, PDF)]
'''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]].


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.


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 price
! 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
|-
|-
! 2018 value
! In 2023 Dollars
|align=right| $3,300
|align=right| $4,100
|align=right| $2,700
|align=right| $3,300
|align=right| $2,770
|align=right| $3,400
|align=right| $3,000
|align=right| $3,700
|align=right| $3,420
|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                       | 7A18 Front
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.
7a18-attenuator.jpg                | 7A18 attenuator opened.  One of the attenuation R/C modules has been unplugged to reveal the switch contacts.
Tek-7603-front.jpg                  | A [[7603]] with two 7A18s
Tek 7a17 7a18 7b50a model3 cart.jpg | 7A18 in [[7613]] mainframe
</gallery>
</gallery>


===Option 06===
'''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

Tektronix 7A18
75 MHz dual channel amplifier
7A18 front view

Compatible with 7000-series scopes

Produced from 1971 to 1992

Manuals

Alternates

(All manuals in PDF format unless noted otherwise)
Manuals – Specifications – Links – Pictures

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
  • Mode: CH1 only, CH2 only, Add CH1+CH2, Alternating, Chopped. CH2 can be inverted.
  • Input sockets with contact ring for probe ×10 / identify information
  • No bandwidth limiter switch
Weight 1.4 kg

Links

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

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

Development Prototypes

7A18A

Option 06

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