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{{Oscilloscope Sidebar|
{{Oscilloscope Sidebar  
title=Tektronix 7844|
|manufacturer=Tektronix
image=Tektronix 7844.JPG|
|series=7000-series scopes
caption=Tektronix 7844, front view<br/>with [[7A26]], [[7A19]](?), [[7B80]] and [[7B85]] |
|model=7844
introduced=1975 |
|summary=400 MHz dual-beam non-storage mainframe
discontinued=1988 |
|image=Tek7844-front.jpg
summary=
|caption=Tektronix 7844 Opt.78 (P11 phosphor)
400MHz dual-beam non-storage mainframe|
|introduced=1974
manuals=
|discontinued=1988  
* [http://bama.edebris.com/manuals/tek/7844/ Tek 7844 Service Manual] at BAMA
|designers=Murlan Kaufman;Chuck Scott;Dick Anderson;Keith Taylor;Bob White
|manuals=
* [[Media:070-1675-00.pdf|7844 Operator Manual]] (OCR)
* [[Media:070-1676-02.pdf|7844 Service Manual]] (OCR)
}}
}}
The '''Tektronix 7844''' is a 400 MHz [[dual-beam scopes|dual-beam CRT oscilloscope]]
The '''Tektronix 7844''' is a 400 MHz [[dual-beam scopes|dual-beam CRT oscilloscope]] that takes two 7000-series vertical plug-ins and two 7000-series horizontal plug-ins.
that takes two 7000-series vertical plug-ins and two 7000-series horizontal plug-ins.


Versions include the 7844 bench-top lab scope and R7844 rack-mount model.
Versions include the 7844 bench-top lab scope and R7844 rack-mount model.


A typical configuration might have included [[7A24]] or [[7A19]] amplifiers, a [[7B80]] and a [[7B85]] timebase.
Circuit design for the 7844 was done by [[Chuck Scott]], [[Dick Anderson]], [[Keith Taylor]], and [[Bob White]]. Project manager for the 7844 was [[Murlan Kaufman]]. 
The [[T7840|7844's CRT]] was designed by [[Conrad Odenthal]] and [[Ken Hawken]].


==Specifications==
A typical configuration might have included [[7A19]] or [[7A24]] amplifiers, [[7B80]]/[[7B85]] or [[7B92A]] timebases.
 
{{BeginSpecs}}
{{Spec | Bandwidth | 400 MHz with [[7A19]], [[7A29]] (eq. 0.9 ns rise time), 300 MHz with [[7A24]] }}
{{Spec | Fastest calibrated sweep | 1 ns/Div (with [[7B80]], [[7B85]], [[7B92A]]) }}
{{Spec | Beam isolation | > 100:1 from DC to 150 MHz, > 30:1 from 150 MHz to 400 MHz }}
{{Spec | X-Y Phase Shift | < 2° from DC to min. 50 kHz }}
{{Spec | Horizontal bandwidth | DC to at least 1 MHz }}
{{Spec | Z axis input | 2 V<sub>p-p</sub> for full intensity range (positive decreases), input impedance 500 Ω, rise time 15  ns, max. 1 MHz }}
{{Spec | CRT | [[T7840]], p/n [[154-0713-00]] with P31 phosphor, or [[154-0713-04]] with P11 phosphor (Opt. 78), acceleration 24 kV (−3/+21) }}
{{Spec | Calibrator | 4 mV, 40 mV, 400 mV or 4 V into >100 kΩ, 0.4 mV, 4 mV, 40 mV or 400 mV into 50 Ω; 1 kHz }}
{{Spec | Power | 90-132 V or 180-264 V, 48 to 440 Hz, max. 235 W }}
{{Spec | Weight | 16.3 kg (36 lbs) / R7844: 15 kg (33 lbs)}}
{{Spec | Options |
* Opt.03 – EMI shielding
* Opt.21 – Dedicated vertical deflection system (eliminates vertical mode switch and crossover board)
* Opt.22 – Enhancer (generates raster scan to illuminate the entire CRT at the end of beam 2 sweep)
* Opt.78 – P11 phosphor
}}
{{EndSpecs}}
 
==Links==
* [https://amplifier.cd/Test_Equipment/Tektronix/Tektronix_7000_series_mainframe/7844.html Tek 7844 page at amplifier.cd] and a [http://www.amplifier.cd/Test_Equipment/Tektronix/Tektronix_7000_series_mainframe/rep-und-kal/7844_reparatur_engl.html repair report (switch-mode PSU)]
* [http://www.barrytech.com/tektronix/tek7000/tek7844.html Tek 7844 @ barrytech.com]
* [http://www.firstpr.com.au/tequip/R7844/ R7844 page with frequency response measurements]
* [http://www.jvgavila.com/tek7844.htm Tek R7844 page @ EB5AGV], lots of internal photos
{{Documents|Link=7844}}


==Internals==
==Internals==
The 7844's CRT has distributed vertical deflection plates.
The [[T7840|7844's CRT]] has [[distributed vertical deflection plates]].  It uses a number of custom ICs, such as [[155-0064-00]], [[155-0065-00]] and [[155-0059-00]] in the vertical amplifiers, [[155-0095-00]] in the vertical interface, [[155-0078-00]] in the  trigger selector, and [[155-0022-00]] in the horizontal interface. The horizontal and Z axis amplifiers are discrete.


The power supply is a resonant switch-mode inverter with linear post-regulation, similar to the one in the [[7904]], unlike which the 7844 does have a fan.
The 7844 is more complex than all other 7000 mainframes except the [[7854]] because vertical and horizontal amplifiers as well as the Z axis control boards exist twice, and there is an extra switching logic board.  As a consequence, verifying correct operation requires testing many possible combinations of settings – for example, a defect on the vertical switching board could cause a problem only in the case of both beam 1 and 2 using horizontal bay B, but not if beam 1 used A and beam 2 used B.
Moreover, calibration and adjustment is significantly more work than in a single-beam scope, e.g. CRT geometry trimpots need to be adjusted for matching both beams, not only for best geometry, and these adjustments even interact slightly.


==Links==
The power supply is a resonant switch-mode inverter with linear post-regulation, similar to the one in the [[7904]].  It uses the [[155-0067-02]] controller.  Despite having an SMPS, the 7844 is fairly heavy behause of the duplicate internal components, especially the second vertical delay line.  The delay lines need extra space and are located vertically to the right of the CRT instead of below the CRT as in other 7xx4s.
 
Unlike some other 7000 series mainframes with switchmode PSUs, the 7844 does have a fan.
 
Early 7844 (SN B109999 and earlier) have issues with horizontal aberrations for sweep rates of 1 ns/Div. After discovery of the issue modification kits (040-0804-00) that replace the horizontal amplifier were offered. For more information see the [[Media:Tek 067-0657-00 with schematics.pdf|manual]] of the [[067-0657-00|067-0657-00 Normalized Ramp Generator]] that was use to investigate this issue.


* [http://amplifier.cd/Test_Equipment/Tektronix/Tektronix_7000_series_mainframe/7844.html Tek 7844 page at amplifier.cd] and a [http://www.amplifier.cd/Test_Equipment/Tektronix/Tektronix_7000_series_mainframe/rep-und-kal/7844_reparatur_engl.html repair report (switch-mode PSU)]
==Prices==
* [http://www.barrytech.com/tektronix/tek7000/tek7844.html Tek 7844 @ barrytech.com]
{| class="wikitable"
|-
! &nbsp;
! Year
! 1976
! 1980
! 1984
! 1990<br />(R7844)
|-
!rowspan=2| Mainframe only
! Catalog price
|align=right|  $6,100
|align=right|  $9,125
|align=right| $13,435
|align=right| $19,500
|-
! In 2023 dollars
|align=right| $32,600
|align=right| $33,700
|align=right| $39,300
|align=right| $45,400
|-
!rowspan=2| Mainframe with 2 × [[7A19]],<br />[[7B85]], [[7B80]]
! Catalog price
|align=right|  $9,500
|align=right| $14,275
|align=right| $21,520
|align=right| $30,660
|-
! In 2023 dollars
|align=right| $50,800
|align=right| $52,700
|align=right| $63,000
|align=right| $71,300
|}


==Pictures==
==Pictures==


<gallery>
<gallery>
File:7844-3.jpg | Simultaneous time and frequency domain display using a [[7A26]] amplifier, [[7B92A]] time base, and [[7L5]] Spectrum Analyzer
Tek7844-front.jpg              | Tektronix 7844 front view
File:Tektronix 7844.JPG|Tektronix 7844
Tek7844-rear.jpg              | Tektronix 7844 rear view
File:Tektronix r7844.jpg|Tektronix R7844
Tek 7844 with 7d15.JPG
File:Wellenkino 7844.jpg
7844-3.jpg                     | Simultaneous time and frequency domain display using a [[7A26]] amplifier, [[7B92A]] time base, and [[7L5]] Spectrum Analyzer
Tektronix 7844.JPG             | Tektronix 7844 front view (with [[7A26]], [[7A19]], [[7B80]] and [[7B85]], Opt.03 CRT EMI screen)
R7844-2.jpg                    | Tektronix R7844
R7844-rear.jpg                 | Tektronix R7844, rear view
Wellenkino 7844.jpg           | 7844 with options 78 (blue P11 phosphor) and 21 (dedicated vertical slots, i.e. no vertical mode switch)
Tek 7844 top.jpg              |
Tek 7844 rear connections.jpg  |
Tek 7844 left.jpg              |
Tek 7844 right.jpg            |
</gallery>
</gallery>
==Interior==
<gallery>
Tek7844-right.jpg              | Right interior.  Top row: Calibrator board (l), [[7000 series readout system|readout board]] (c), beam 2 vertical amplifier (r), fan.
Tek7844-right-above.jpg        | Right/above interior.  The dual delay lines can be seen behind the readout board.  Horizontally mounted boards in the center are: Crossover mode switch (l), trigger selector (c), power supply (r).
Tek7844-v-b2.jpg              | Beam 2 vertical amplifier, CRT and termination detail (right side)
Tek7844-left.jpg              | Left interior.  Beam 1 vertical amplifier (l), crossover vertical interface (r).
Tek7844-left-above.jpg        | Left/above interior.  Top row: Beam 1 Z axis (l), Beam 1 / Beam 2 horizontal amplifiers (c/r).
Tek-7844-vmode-back.jpg        | Vertical mode switch board, back side
Tek-7844-vmode-back-detail.jpg | Vertical mode switch board, back side (detail)
</gallery>
===Option 22===
<gallery>
Tek 7844 with Opt 22.jpg      | An 7844 with option 22 (board right of the readout).
Tek 7844 Opt 22 board 1.jpg    | Opt. 22 board
Tek 7844 Opt 22 board 2.jpg    | Readout board (l), Opt. 22 board (r)
Tek 7844 Opt 22 board 3.jpg    | Opt. 22 board
</gallery>
==Components==
{{Parts|7844}}
{{Custom ICs|7000 series readout system}}


[[Category:7000 series non-storage mainframes]]
[[Category:7000 series non-storage mainframes]]
[[Category:Dual beam scopes]]
[[Category:Dual beam scopes]]
[[Category:Specifications needed]]
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