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{{Oscilloscope Sidebar|
{{Oscilloscope Sidebar  
title=Tektronix 7844|
|manufacturer=Tektronix
image=Tek7844-front.jpg|
|series=7000-series scopes
caption= |
|model=7844
introduced=1975 |
|summary=400 MHz dual-beam non-storage mainframe
discontinued=1988 |
|image=Tek7844-front.jpg
summary=
|caption=  
400 MHz 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=
* [http://w140.com/mmm/tek-7844.pdf Tektronix 7844 Service Manual (October 1981 Revision, 070-1676-02 265MB, PDF)]
* [http://exodus.poly.edu/~kurt/manuals/manuals/Tektronix/TEK%207844%20R7844%20Instruction.pdf 7844/R7844 Operator's Manual] (Rev. 11/1981, PDF, 3 MB)
* [http://bama.edebris.com/manuals/tek/7844/ Tek 7844 Service Manual] at BAMA (Rev. 02/Oct 1981, 070-1676-02 PDF, 109 MB)
}}
}}
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.
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]].


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.
A typical configuration might have included [[7A19]] or [[7A24]] amplifiers, [[7B80]]/[[7B85]] or [[7B92A]] timebases.


{{BeginSpecs}}
{{BeginSpecs}}
{{Spec | Bandwidth | 400 MHz (with [[7A19]], [[7A29]]) eq. 0.9 ns rise time }}
{{Spec | Bandwidth | 400 MHz with [[7A19]], [[7A29]] (eq. 0.9 ns rise time), 300 MHz with [[7A24]] }}
{{Spec | Fastest calibrated sweep | 1 ns (with [[7B80]], [[7B85]]) }}
{{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 | 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 | Weight | 16.3 kg (36 lbs) / R7844: 15 kg (33 lbs)}}
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==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]].  Despite this, the 7844 is fairly heavy, which is mostly due to 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.
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.


Unlike other 7000 series mainframes with switch mode PSUs, the 7844 does have a fan.   
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.


The 7844 is more complex than all other 7000 mainframes because vertical and horizontal amplifiers as well as the Z axis control boards exist twice, and there is an extra switching logic board.
Unlike some other 7000 series mainframes with switch mode PSUs, the 7844 does have a fan.


==Links==
==Links==


* [[Media:Tekscope_1974_V6_N4.pdf | A 400 MHz dual-beam oscilloscope. Tekscope Vol.6 No.4, Sept/Oct 1974]]
* [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)]
* [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)]
* [http://www.barrytech.com/tektronix/tek7000/tek7844.html Tek 7844 @ barrytech.com]
* [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.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
* [http://www.jvgavila.com/tek7844.htm Tek R7844 page @ EB5AGV], lots of internal photos
==Prices==
==Prices==
{| class="wikitable"
{| class="wikitable"
Line 56: Line 71:
|align=right| $19,500
|align=right| $19,500
|-
|-
! 2014 value
! 2018 value
|align=right| $25,320
|align=right| $26,690
|align=right| $26,150
|align=right| $27,570
|align=right| $30,540
|align=right| $32,200
|align=right| $35,230
|align=right| $37,150
|-
|-
!rowspan=2| Mainframe with 2 × [[7A19]],<br />[[7B85]], [[7B80]]
!rowspan=2| Mainframe with 2 × [[7A19]],<br />[[7B85]], [[7B80]]
Line 69: Line 84:
|align=right| $30,660
|align=right| $30,660
|-
|-
! 2014 value
! 2019 value
|align=right| $39,430
|align=right| $41,570
|align=right| $40,910
|align=right| $43,140
|align=right| $48,910
|align=right| $51,570
|align=right| $55,400
|align=right| $58,410
|}
|}
==Pictures==
==Pictures==


<gallery>
<gallery>
File:Tek7844-front.jpg   | Tektronix 7844 front view
Tek7844-front.jpg             | Tektronix 7844 front view
File:Tek7844-rear.jpg   | Tektronix 7844 rear view
Tek7844-rear.jpg               | Tektronix 7844 rear view
File:7844-3.jpg         | Simultaneous time and frequency domain display using a [[7A26]] amplifier, [[7B92A]] time base, and [[7L5]] Spectrum Analyzer
Tek 7844 with 7d15.JPG
File:Tektronix 7844.JPG |Tektronix 7844 front view (with [[7A26]], [[7A19]](?), [[7B80]] and [[7B85]])
7844-3.jpg                     | Simultaneous time and frequency domain display using a [[7A26]] amplifier, [[7B92A]] time base, and [[7L5]] Spectrum Analyzer
File:Tektronix r7844.jpg |Tektronix R7844
Tektronix 7844.JPG             | Tektronix 7844 front view (with [[7A26]], [[7A19]](?), [[7B80]] and [[7B85]])
File:Wellenkino 7844.jpg | 7844 with options 78 (blue P11 phosphor) and 21 (dedicated vertical slots, i.e. no vertical mode switch)
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==
==Interior==
<gallery>
<gallery>
File:Tek7844-right.jpg         | Right interior.  Top row: Calibrator board (l), [[7000 series readout system|readout board]] (c), beam 2 horizontal amplifier (r), fan.  
Tek7844-right.jpg             | Right interior.  Top row: Calibrator board (l), [[7000 series readout system|readout board]] (c), beam 2 vertical amplifier (r), fan.  
File: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-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).
File:Tek7844-v-b2.jpg         | Beam 2 vertical amplifier, CRT and termination detail (right side)
Tek7844-v-b2.jpg               | Beam 2 vertical amplifier, CRT and termination detail (right side)
File:Tek7844-left.jpg         | Left interior.  Beam 1 vertical amplifier (l), crossover vertical interface (r).
Tek7844-left.jpg               | Left interior.  Beam 1 vertical amplifier (l), crossover vertical interface (r).
File:Tek7844-left-above.jpg   | Left/above interior.  Top row: Beam 1 Z axis (l), Beam 1 / Beam 2 horizontal amplifiers (c/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.jpg        | Vertical mode switch board, back side
Tek-7844-vmode-back-detail.jpg | Vertical mode switch board, back side (detail)
Tek-7844-vmode-back-detail.jpg | Vertical mode switch board, back side (detail)
</gallery>
</gallery>
{{Custom ICs|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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