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{{Oscilloscope Sidebar|
{{Oscilloscope Sidebar  
title=Tektronix 7904|
|manufacturer=Tektronix
image=Tek-7904-front.jpg |
|series=7000-series scopes
caption=Tektronix 7904 (with [[7A19]], [[7A11]], [[7D11]], [[7B85]]) |
|model=7904
introduced=1971 |
|designers=Val Garuts;Thor Hallen;John McCormick;Les Larson;Bill DeVey;Bill Peek;Hans Springer;Joe Burger;Joel Swanno;Ken Hawken
discontinued=1990 |
|image=Tek-7904-front.jpg
summary=500 MHz non-storage mainframe|
|caption=Tektronix 7904 (with [[7A19]], [[7A11]], [[7D11]], [[7B85]])  
manuals=
|introduced=1971  
* [http://bama.edebris.com/download/tek/7904/Tektronix_7904_Service_May1983.pdf Tektronix 7904 Manual (PDF)]
|discontinued=1984
* [http://www.ko4bb.com/getsimple/index.php?id=manuals&dir=Tektronix/Tektronix_-_7904A Tektronix 7904A Manual (DjVu)]
|summary=500 MHz non-storage mainframe
* [http://w140.com/Tektronix_7904A_OCRed_by_Tabalabs.pdf Tektronix 7904A Manual (Shannon Hill PDF with OCR)]
|manuals=
* [http://w140.com/Tek_7904_OCRed_by_Tabalabs.pdf Tektronix 7904 Manual (Shannon Hill PDF with OCR)]
'''7904'''
* [http://w140.com/Tek_7904_Power_Supply.pdf Servicing the 7904 High-Efficiency Power Supply (PDF)]
* [[Media:070-1399-00.pdf|Tektronix 7904 Operators Manual]]
* [[Media:070-2390-00.pdf|Tektronix 7904 Instruction Manual with PSU Schematics]] SN B260000+ (OCR)
* [[Media:070-2390-02.pdf|Tektronix 7904 Instruction Manual with complete schematics]] Below SNB260000 (Needs OCR)
* [[Media:Servicing the Tek 7904 Power Supply.pdf|Servicing the 7904 High-Efficiency Power Supply]]
* [[Media:Tektronix - 7904 - Horizontal Amplifier B010100 - B079999.pdf|Horizontal Amplifier SN B010100 - B079999]]
<small>
'''Modifications'''
* [https://hakanh.com/dl/docs/kitinstructions/050-0650-00.pdf 050-0650-00 (1980) Vertical amplifier IC replacement]
* [https://hakanh.com/dl/docs/kitinstructions/050-0651-01.pdf 050-0651-01 (1975) Vertical output IC replacement (155-0065-00)]
* [https://hakanh.com/dl/docs/kitinstructions/050-0706-01.pdf 050-0706-01 (1980) Vertical output IC replacement (155-0065-00)]
* [https://hakanh.com/dl/docs/kitinstructions/050-0729-06.pdf 050-0729-06 (1980) A Trigger selector circuit board replacement]
* [https://hakanh.com/dl/docs/kitinstructions/050-0730-06.pdf 050-0730-06 (1980) B Trigger selector circuit board replacement]
* [https://hakanh.com/dl/docs/kitinstructions/050-0763-03.pdf 050-0763-03 (1981) Vertical interface circuit board replacement]
* [https://hakanh.com/dl/docs/kitinstructions/050-1014-00.pdf 050-1014-00 (1980) Vertical output IC replacement] ([[155-0064-00]])
* [https://hakanh.com/dl/docs/kitinstructions/050-1723-01.pdf 050-1723-01 (1983) P31 CRT replacement]
* [https://hakanh.com/dl/docs/custommods/7904mod721K.pdf Custom Mod 721K (1972) Single shot readout and/or grat illumination]
</small>
}}
}}
The '''Tektronix 7904''' is a 500 MHz, non-storage 7000-series oscilloscope mainframe with four bays. It accepts two [[7000-series_plug-ins#Vertical plug-ins|7000-series vertical plug-ins]] and two [[7000-series_plug-ins#Horizontal plug-ins|7000-series horizontal plug-ins]]. It was introduced in late 1971/early 1972 (Note 1).  The successor model 7904A was introduced in 1984. There is also a rack-mount version, the [[R7903]], albeit with only one horizontal bay.
The '''Tektronix 7904''' is a 500 MHz, non-storage 7000-series oscilloscope mainframe with four bays.
It accepts two [[7000-series_plug-ins#Vertical plug-ins|7000-series vertical plug-ins]] and two [[7000-series_plug-ins#Horizontal plug-ins|7000-series horizontal plug-ins]].
There is also a rack-mount version, the [[R7903]], albeit with only one horizontal bay.


Performance is largely determined by the plug-ins. The [[7A19]] vertical amplifier and [[7B92]] time base were introduced along with the 7904 to match the 500 MHz system bandwidth.   
The 7904 was introduced in late 1971/early 1972 (Note 1). In 1984, it was replaced by the redesigned [[7904A]].
 
Performance is largely determined by the plug-ins.
The [[7A19]] vertical amplifier and [[7B92]] time base were introduced along with the 7904 to match the 500 MHz system bandwidth.   
 
Design Staff of 7904 Project (from July 1971 Tekscope):
<blockquote>[[Val Garuts]] was project manager and developed the large signal amplifier circuit used in the horizontal and Z-axis amplifiers. [[Thor Hallen]] did the [[7A19]] plug-in and the vertical amplifier, and [[John McCormick]] the horizontal. The trigger and time base ([[7B92]] plug-in) were done by [[Les Larson]] and [[Bill DeVey]]. [[Bill Peek]] worked on the Z-axis amplifier and auto-focus, with [[Hans Springer]] doing the mainframe interface and channel switching. [[Joe Burger]]'s work on the power supply, coupled with [[Joel Swanno]]’s efforts in mechanical design, reduced the weight to only 30 pounds. [[Ken Hawken]] did the fine job on the CRT. </blockquote>


{{BeginSpecs}}
{{BeginSpecs}}
{{Spec | Bandwidth | 500 MHz }}
{{Spec | Bandwidth | 500 MHz (with [[7A19]] or [[7A29]] amplifier) }}
{{Spec | Fastest calibrated sweep | 500 ps/Div (with [[7B92A]], other time bases "uncalibrated for first 60 ns") }}
{{Spec | Fastest calibrated sweep | 500 ps/Div (with [[7B92A]], other time bases "uncalibrated for first 60 ns") }}
{{Spec | Acceleration voltage | 24 kV (+21 / -3 kV) }}
{{Spec | Outputs | Vertical Signal Out (25 mV/Div into 50 Ω, 0.5 V/Div into 1 MΩ); +Sawtooth; +Gate; camera power; probe power }}
{{Spec | Calibrator (7904) | 4 mV, 40 mV, 400 mV, 4 V or 40 V (p-p) into 1 MΩ; 2 mV, 20 mV, 200 mV or 400 mV into 50 Ω; or 40 mA; selectable 1 kHz, ½ rep. rate of B Sweep Gate, or DC }}
{{Spec | Inputs | Z Axis (15 V<sub>p-p</sub>) }}
{{Spec | Calibrator (7904A) | 4 mV to 4 V (p-p) in decade steps, 1 kHz; 40 mV to 400 mV into 50 Ω }}
{{Spec | CRT |
{{Spec | Power consumption | 190 W }}
* Standard: (8×10 Div @ 1 cm), P31 (green) [[154-0644-05]] or P11 (blue) [[154-0644-09]], acceleration voltage 24 kV (+21 / –3 kV)
{{Spec | Weight | 13.5 kg (30 lbs) }}
{{Spec | CRT Options |
* Standard: (8×10 Div @ 1 cm), P31 (green) [[154-0644-05]] or P11 (blue) [[154-0644-09]]
* Option 4, high writing speed: (8×10 Div @ 0.5 cm) , P31 (green) [[154-0661-05]] or P11 (blue) [[154-0661-09]]
* Option 4, high writing speed: (8×10 Div @ 0.5 cm) , P31 (green) [[154-0661-05]] or P11 (blue) [[154-0661-09]]
}}
}}
{{EndSpecs}}
{{Spec | Calibrator | DC, square wave (1 kHz or ½ B Sweep gate), 4 mV to 40 V in decade steps (2/20/200/400 mV into 50 Ω); 40 mA current loop }}
 
{{Spec | Power | 90−132 V or 180−264 V, 48−440 Hz, 190 W max. }}
===7904A differences===
{{Spec | Weight | 13.5 kg (30 lbs) }}
The 7904 had an elaborate 5-decade built-in calibrator with variable rate that was dropped from the 7904A.  In the 7904A, The Control Illumination switch moved to the rear panel, and the [[7000 series readout system|readout system]] gained a pulsed mode in which it is synchronized with the sweep instead of interrupting the display at random times.  This pulsed mode is not compatible with all time base plug-ins (see manual p. 1-12).
{{Spec | Dimensions | 34.2 cm × 30.5 cm × 69.5 cm (13.5 in x 12.0 in x 23.8 in) H×W×L }}
 
{{Spec|Options|
===Options===
* Opt.1: deletes read out system
<div style="column-count:4;-moz-column-count:4;-webkit-column-count:4">
* Opt.2: X-Y delay compensation network
* Opt.2: X-Y delay compensation network
* Opt.3: Extra EMI shielding
* Opt.3: Extra EMI shielding
* Opt.4: Maximum-brightness CRT with reduced area
* Opt.4: Maximum-brightness CRT with reduced area
* Opt.78: P11 phosphor
* Opt.78: P11 phosphor
</div>
}}
{{EndSpecs}}
 
==Links==
* [https://lazyelectrons.wordpress.com/2018/11/24/tektronix-7904-oscilloscope-power-supply-repair/ 7904 Repair with Video]
* [http://amplifier.cd/Test_Equipment/Tektronix/Tektronix_7000_series_mainframe/7904.htm Tek 7904]  @ amplifier.cd
* [https://www.circuitsathome.com/measurements/repairing-front-panel-buttons-of-tektronix-7904-oscilloscope Repairing front panel buttons of Tektronix 7904 oscilloscope]
{{Documents|Link=7904}}
{{PatentLinks|7904}}


==Operation==
==Operation==
The 7904 has many modes of operation.
One mode is called "Independent-Pairs Display" in the manual, where the input to the left vertical plug-in is displayed using the B horizontal time-base plug-in,
and the input to the right vertical plug-in is displayed using the A horizontal time-base plug-in.
This resembles the trace-slaving "ALT" mode that is produced by an [[1A4]] in a [[547]]. Many other modes are available.
It is possible to put vertical plug-ins in the horizontal slots for X-Y operation.
It is even possible to put a horizontal plug-in in one of the vertical slots to produce a raster scan. 


The 7904 has a many modes of operation.  One mode is called "Independent-Pairs Display" in the manual, where the input to the left vertical plug-in is displayed using the B horizontal time-base plug-in, and the input to the right vertical plug-in is displayed using the A horizontal time-base plug-in. This resembles the trace-slaving "ALT" mode that is produced by an [[1A4]] in a [[547]].  Many other modes are available.  It is possible to put vertical plug-ins in the horizontal slots for X-Y operation.  It is even possible to put a horizontal plug-in in one of the vertical slots to produce a raster scan.  
A special plug-in, the [[7A21N]], provides direct access to the deflection plates up to 1 GHz at an uncalibrated sensitivity of 4 V/Div.
This plugin requires modifications to the mainframe to bypass the Y output amplifier (thus disabling readout and the other vertical plugin bay).


A special plug-in, the [[7A21N]], provides direct access to the deflection plates up to 1 GHz at an uncalibrated sensitivity of 4 V/Div.  This plugin requires modifications to the mainframe to bypass the Y output amplifier (thus disabling readout and the other vertical plugin bay).
A rear-panel [[7904 remote control connector| remote control connector]] has connections for single-sweep ready lamps, a reset button, and readout control.


==Internals==
==Internals==
The 7904 uses a switch-mode power supply and has no fan. It incorporates a 65 ns Y delay line.  This delay is too short for some older time bases such as [[7B53]] to display the trigger event.
The 7904 uses a switch-mode power supply and has no fan. The signal path is completely differential and the internal signal wiring is 50 Ω coax.


[[Thor Hallen]] designed the main vertical amplifier and the [[7A19]] plugin (Note 1).  It used bridged T coils and the "[[Transit frequency doubler|f<sub>t</sub> doubler]]" circuit patented by [[Carl Battjes]] to achieve its bandwidth.
The Y delay line in the 7904 has a delay of 65 ns, which is too short for some older time bases such as [[7B53]] to display the trigger event.
The CRT ([[154-0644-05]]) has [[distributed vertical deflection plates]].


The 7904 makes extensive use of custom integrated circuits and hybrid circuits, inter alia, the [[155-0064-00]] 470-ps output amplifier, [[155-0022-00]] analog multiplexer for channel switching, [[155-0059-00]] HF amplifier, [[155-0095-01]] and [[155-0095-03]] differential HF amplifiers, and [[155-0067-02]] SMPS controller.
[[Thor Hallen]] designed the main vertical amplifier and the [[7A19]] plugin (Note 1).
It used bridged T coils and the "[[ft doubler|f<sub>t</sub> doubler]]" circuit patented by [[Carl Battjes]] to achieve its bandwidth.


The 7904A includes [[155-0173-05]], [[155-0175-05]] and [[155-0178-05]] amplifiers.
The 7904 makes extensive use of custom integrated circuits and hybrid circuits, inter alia, the [[155-0064-00]] 470-ps output amplifier,
[[155-0022-00]] analog multiplexer for channel switching, [[155-0059-00]] HF amplifier,
[[155-0095-01]] and [[155-0095-03]] differential HF amplifiers, and [[155-0067-02]] SMPS controller.


The signal path is completely differential and all of the internal wiring is 50 Ω coax. The CRT ([[154-0644-05]]) has [[distributed vertical deflection plates]].
Early 7904 have issues with horizontal aberrations for sweep rates of 1 ns/Div or faster. After discovery of the issue modification kits that replace the horizontal amplifier were offered. For more information see the table below and the [[Media:Tek 067-0657-00 with schematics.pdf|manual]] of the [[067-0657-00|067-0657-00 Normalized Ramp Generator]] that was used to investigate and rectify this issue.
{| class="wikitable"
|-
! Serial Number
! A9 Horizontal Amp.
! Issue
! Modification Kit
|-
|B010000-B081987
||670-1632-00
|Fully calibrated sweeps for rates of 1 ns/Div or faster requires a dedicated [[7B92]] (non A!) and the two units to be calibrated as a system.
|050-0636-01
|-
|B081988-B219999
||670-1632-01
|Can be calibrated to either work with magnifier timebases ([[7B70]],[[7B80]]), or alternatively non-magnifying time bases ([[7B92A]]), but not both.
|040-0791-00
|-
|B220000 and above
|670-1632-02/03
|None - fully compatible with all timebases and all sweep rates.
|−
|}


==Prices==
==Prices==
Line 67: Line 128:
! 1976
! 1976
! 1980
! 1980
! 1984
! 1990
|-
|-
! Model
! Model
Line 75: Line 134:
|align=center| 7904
|align=center| 7904
|align=center| 7904
|align=center| 7904
|align=center| 7904A
|align=center| 7904A
|-
|-
!rowspan=2| Mainframe only
!rowspan=2| Mainframe only
Line 83: Line 140:
|align=right|  $4,100
|align=right|  $4,100
|align=right|  $6,265
|align=right|  $6,265
|align=right|  $8,810
|align=right| $12,750
|-
|-
! 2014 value
! In 2024 Dollars
|align=right| $16,500
|align=right| $21,800
|align=right| $17,150
|align=right| $22,600
|align=right| $18,080
|align=right| $23,900
|align=right| $20,170
|align=right| $23,200
|-
|-
!rowspan=2| Mainframe with [[7A19]],<br />7A19 Opt. 04, [[7B92]]
!rowspan=2| Mainframe with [[7A19]],<br />7A19 Opt. 04, [[7B92]]
Line 98: Line 151:
|align=right|  $7,765
|align=right|  $7,765
|align=right| $12,015
|align=right| $12,015
|align=right| $17,425
|align=right| $24,190
|-
|-
! 2014 value
! In 2024 Dollars
|align=right| $31,320
|align=right| $41,300
|align=right| $32,480
|align=right| $42,900
|align=right| $34,710
|align=right| $45,800
|align=right| $39,920
|align=right| $44,050
|}
|}
==Links==
* [[Media:Tekscope 1971 V3 N4 Jul 1971.pdf | Tekscope Vol. 3 No. 4, Jul 1971]]
* [http://amplifier.cd/Test_Equipment/Tektronix/Tektronix_7000_series_mainframe/7904.htm Tek 7904] / [http://amplifier.cd/Test_Equipment/Tektronix/Tektronix_7000_series_mainframe/7904A.htm 7904A] @ amplifier.cd
* [http://www.barrytech.com/tektronix/tek7000/tek7904.html Tek 7904] / [http://www.barrytech.com/tektronix/tek7000/tek7904a.html 7904A] @ barrytech.com
* [https://www.circuitsathome.com/measurements/repairing-front-panel-buttons-of-tektronix-7904-oscilloscope Repairing front panel buttons of Tektronix 7904 oscilloscope]


==Notes==
==Notes==
# See [[7A11]] and [[John Addis]], ''Good Engineering and Fast Vertical Amplifiers'', in Jim Williams (Ed.), ''Analog Circuit Design: Art, Science and Personalities'' (1991), p.114, and [http://w140.com/tektronix_new_products_1972.pdf Tektronix New Products 1972] brochure.
# See [[7A11]] and [[John Addis]], ''Good Engineering and Fast Vertical Amplifiers'', in [[Jim Williams]] (Ed.), ''Analog Circuit Design: Art, Science and Personalities'' (1991), p.114, and [[Media:Tektronix_New_Products_March_1972.pdf|Tektronix New Products 1972]] brochure.
   
   
==Pictures==
==Pictures==


===7904 non-A===
<gallery>
<gallery>
File:Tek-7904-front.jpg | 7904  (non-A) front
Tek-7904-front.jpg | 7904  (non-A) front
File:7904-left.jpg | Left side. Left top: Vertical amplifier; left bottom: switch-mode power supply; right center: delay line; right bottom: plug-in bays
Tek 7904 rear.jpg | 7904 rear
File:7904-right.jpg | Right side.  Top left: calibrator; bottom left: plug-in bays; top center: [[7000 series readout system|readout board]];  top right: Z amplifier  
7904-left.jpg | Left side. Left top: Vertical amplifier; left bottom: switch-mode power supply; right center: delay line; right bottom: plug-in bays
File:7904-right-front.jpg | Right side detail. Left: calibrator; right: readout.
7904-right.jpg | Right side.  Top left: calibrator; bottom left: plug-in bays; top center: [[7000 series readout system|readout board]];  top right: Z amplifier  
File:7904 interface 1.jpg|Plug-in backplane board front (left trigger selector piggyback board removed)
7904-right-front.jpg | Right side detail. Left: calibrator; right: readout.
File:Tek7904-trig-selector.jpg | B Trigger selector piggyback board (A6)
7904 interface 1.jpg|Plug-in backplane board front (left trigger selector piggyback board removed)
File:Tek7904-vertical-interface.jpg | Vertical interface piggyback board (A7).  The two [[155-0095-03]] amplifiers (large metal cans) are used to select the signal from one vertical plug-in bay, and drive the delay line.
Tek7904-trig-selector.jpg | B Trigger selector piggyback board (A6)
File:7904 interface 2.jpg|Plug-in backplane board rear
Tek7904-vertical-interface.jpg | Vertical interface piggyback board (A7).  The two [[155-0095-03]] amplifiers (large metal cans) are used to select the signal from one vertical plug-in bay, and drive the delay line.
File:Tek7904-backplane-bottom.jpg | Backplane board sandwich seen from below
7904 interface 2.jpg|Plug-in backplane board rear
File:7904-x-amp.jpg | Horizontal (X) amplifier board
Tek7904-backplane-bottom.jpg | Backplane board sandwich seen from below
File:7904-y-amp.jpg | Vertical (Y) amplifier board
7904-x-amp.jpg | Horizontal (X) amplifier board (late >B220000)
File:7904-z-amp.jpg | Z amplifier board
7904-y-amp.jpg | Vertical (Y) amplifier board
File:7904-controls.jpg | front-panel controls
7904-z-amp.jpg | Z amplifier board
File:7904_block.gif|7904 block diagram
7904-controls.jpg | front-panel controls
File:Tek7904-7a19-7b92a-1010mhz-hfsync.jpg | A 7B92A (B098xxx) displaying a 1.01 GHz sine in HF Sync mode ([[7904]] mainframe, [[7A19]] amplifier).
7904_block.gif|7904 block diagram
Tek7904-7a19-7b92a-1010mhz-hfsync.jpg | A 7B92A (B098xxx) displaying a 1.01 GHz sine in HF Sync mode ([[7904]] mainframe, [[7A19]] amplifier).
</gallery>


</gallery>
====Power Supply====
====Power Supply====
<gallery>
<gallery>
File:7904-psu-internal.jpg    | 7904 switchmode power supply, covers removed
7904-psu-internal.jpg    | 7904 switchmode power supply, covers removed
File:7904-psu-right.jpg        | View from right (as seen from front of instrument)
7904-psu-right.jpg        | View from right (as seen from front of instrument)
File:7904-psu-primary.jpg      | Primary side circuit board
7904-psu-primary.jpg      | Primary side circuit board
File:7904-psu-primary-caps.jpg | Primary side capacitors
7904-psu-primary-caps.jpg | Primary side capacitors
File:7904-psu-transformer.jpg  | Detail view of transformer from the side
7904-psu-transformer.jpg  | Detail view of transformer from the side
File:7904-psu-rectifier.jpg    | Secondary side rectifier board
Tek_7904_SMPS-xformer.jpeg| Switching transformer
File:7904-psu-regulator.jpg    | Secondary side post-regulator
7904-psu-rectifier.jpg    | Secondary side rectifier board
</gallery>
7904-psu-regulator.jpg    | Secondary side post-regulator
 
Tek_7904_SMPS-HV-Block.jpeg| HV block, multiplier
===7904A===
<gallery>
File:7904A_1.JPG|7904A
File:7904a lvps1.png|7904A Low-voltage Power Supply Schematic
</gallery>
</gallery>


==Parts==
{{Parts|7904}}
{{Custom ICs|7000 series readout system}}


[[Category:7000 series non-storage mainframes]]
[[Category:7000 series non-storage mainframes]]

Latest revision as of 04:37, 26 September 2024

Tektronix 7904
500 MHz non-storage mainframe
Tektronix 7904 (with 7A19, 7A11, 7D11, 7B85)

Produced from 1971 to 1984

Manuals

7904

Modifications

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

The Tektronix 7904 is a 500 MHz, non-storage 7000-series oscilloscope mainframe with four bays. It accepts two 7000-series vertical plug-ins and two 7000-series horizontal plug-ins. There is also a rack-mount version, the R7903, albeit with only one horizontal bay.

The 7904 was introduced in late 1971/early 1972 (Note 1). In 1984, it was replaced by the redesigned 7904A.

Performance is largely determined by the plug-ins. The 7A19 vertical amplifier and 7B92 time base were introduced along with the 7904 to match the 500 MHz system bandwidth.

Design Staff of 7904 Project (from July 1971 Tekscope):

Val Garuts was project manager and developed the large signal amplifier circuit used in the horizontal and Z-axis amplifiers. Thor Hallen did the 7A19 plug-in and the vertical amplifier, and John McCormick the horizontal. The trigger and time base (7B92 plug-in) were done by Les Larson and Bill DeVey. Bill Peek worked on the Z-axis amplifier and auto-focus, with Hans Springer doing the mainframe interface and channel switching. Joe Burger's work on the power supply, coupled with Joel Swanno’s efforts in mechanical design, reduced the weight to only 30 pounds. Ken Hawken did the fine job on the CRT.

Key Specifications

Bandwidth 500 MHz (with 7A19 or 7A29 amplifier)
Fastest calibrated sweep 500 ps/Div (with 7B92A, other time bases "uncalibrated for first 60 ns")
Outputs Vertical Signal Out (25 mV/Div into 50 Ω, 0.5 V/Div into 1 MΩ); +Sawtooth; +Gate; camera power; probe power
Inputs Z Axis (15 Vp-p)
CRT
  • Standard: (8×10 Div @ 1 cm), P31 (green) 154-0644-05 or P11 (blue) 154-0644-09, acceleration voltage 24 kV (+21 / –3 kV)
  • Option 4, high writing speed: (8×10 Div @ 0.5 cm) , P31 (green) 154-0661-05 or P11 (blue) 154-0661-09
Calibrator DC, square wave (1 kHz or ½ B Sweep gate), 4 mV to 40 V in decade steps (2/20/200/400 mV into 50 Ω); 40 mA current loop
Power 90−132 V or 180−264 V, 48−440 Hz, 190 W max.
Weight 13.5 kg (30 lbs)
Dimensions 34.2 cm × 30.5 cm × 69.5 cm (13.5 in x 12.0 in x 23.8 in) H×W×L
Options
  • Opt.1: deletes read out system
  • Opt.2: X-Y delay compensation network
  • Opt.3: Extra EMI shielding
  • Opt.4: Maximum-brightness CRT with reduced area
  • Opt.78: P11 phosphor

Links

Documents Referencing 7904

Document Class Title Authors Year Links
Tekscope 1971 V3 N4 Jul 1971.pdf Article A Subnanosecond Realtime Oscilloscope Val Garuts • Thor Hallen 1971 7904 • 154-0644-00 • 7A19 • Ft doubler • 7B92
7000 series brochure March 1973.pdf Brochure 7000 series brochure, March 1973 1973 7A11 • 7A12 • 7A13 • 7A14 • 7A15A • 7A16A • 7A17 • 7A18 • 7A19 • 7A21N • 7A22 • 7B50 • 7B53A • 7B70 • 7B71 • 7B92 • 7CT1N • 7D11 • 7D13 • 7D14 • 7D15 • 7M11 • 7L12 • 7S11 • 7S12 • 7T11 • 7704A • R7704 • 7904 • R7903 • 7603 • R7603 • 7403N • R7403N • 7313 • R7313 • 7613 • R7613 • 7623 • R7623 • P7001
Tekscope 1974 V6 N3.pdf Article Servicing the 7904 high-efficiency power supply 1974 7904

Patents that may apply to 7904

Page Title Inventors Filing date Grant date Links
Patent US 3453403A Power selection device Eldon Hoffman 1966-08-18 1969-07-01 115 • 140 • 141 • 141A • 144 • 145 • 146 • 147 • 148 • 149 • 149A • 230 • 284 • 286 • 453 • 454 • 491 • 520A • 521A • 522 • 545B • 547 • 556 • 561B • 564B • 568 • 576 • 611 • 647A • 2101 • 2601 • 5030 • R5030 • 5031 • R5031 • 7503 • 7504 • 7704 • 7704A • 7904 • R7903

Operation

The 7904 has many modes of operation. One mode is called "Independent-Pairs Display" in the manual, where the input to the left vertical plug-in is displayed using the B horizontal time-base plug-in, and the input to the right vertical plug-in is displayed using the A horizontal time-base plug-in. This resembles the trace-slaving "ALT" mode that is produced by an 1A4 in a 547. Many other modes are available. It is possible to put vertical plug-ins in the horizontal slots for X-Y operation. It is even possible to put a horizontal plug-in in one of the vertical slots to produce a raster scan.

A special plug-in, the 7A21N, provides direct access to the deflection plates up to 1 GHz at an uncalibrated sensitivity of 4 V/Div. This plugin requires modifications to the mainframe to bypass the Y output amplifier (thus disabling readout and the other vertical plugin bay).

A rear-panel remote control connector has connections for single-sweep ready lamps, a reset button, and readout control.

Internals

The 7904 uses a switch-mode power supply and has no fan. The signal path is completely differential and the internal signal wiring is 50 Ω coax.

The Y delay line in the 7904 has a delay of 65 ns, which is too short for some older time bases such as 7B53 to display the trigger event. The CRT (154-0644-05) has distributed vertical deflection plates.

Thor Hallen designed the main vertical amplifier and the 7A19 plugin (Note 1). It used bridged T coils and the "ft doubler" circuit patented by Carl Battjes to achieve its bandwidth.

The 7904 makes extensive use of custom integrated circuits and hybrid circuits, inter alia, the 155-0064-00 470-ps output amplifier, 155-0022-00 analog multiplexer for channel switching, 155-0059-00 HF amplifier, 155-0095-01 and 155-0095-03 differential HF amplifiers, and 155-0067-02 SMPS controller.

Early 7904 have issues with horizontal aberrations for sweep rates of 1 ns/Div or faster. After discovery of the issue modification kits that replace the horizontal amplifier were offered. For more information see the table below and the manual of the 067-0657-00 Normalized Ramp Generator that was used to investigate and rectify this issue.

Serial Number A9 Horizontal Amp. Issue Modification Kit
B010000-B081987 670-1632-00 Fully calibrated sweeps for rates of 1 ns/Div or faster requires a dedicated 7B92 (non A!) and the two units to be calibrated as a system. 050-0636-01
B081988-B219999 670-1632-01 Can be calibrated to either work with magnifier timebases (7B70,7B80), or alternatively non-magnifying time bases (7B92A), but not both. 040-0791-00
B220000 and above 670-1632-02/03 None - fully compatible with all timebases and all sweep rates. −

Prices

  Year 1972 1976 1980
Model 7904 7904 7904
Mainframe only Catalog price $2,900 $4,100 $6,265
In 2024 Dollars $21,800 $22,600 $23,900
Mainframe with 7A19,
7A19 Opt. 04, 7B92 		Catalog price $5,500 $7,765 $12,015
In 2024 Dollars $41,300 $42,900 $45,800

Notes

  1. See 7A11 and John Addis, Good Engineering and Fast Vertical Amplifiers, in Jim Williams (Ed.), Analog Circuit Design: Art, Science and Personalities (1991), p.114, and Tektronix New Products 1972 brochure.

Pictures

  • 7904 (non-A) front

    7904 (non-A) front

  • 7904 rear

    7904 rear

  • Left side. Left top: Vertical amplifier; left bottom: switch-mode power supply; right center: delay line; right bottom: plug-in bays

    Left side. Left top: Vertical amplifier; left bottom: switch-mode power supply; right center: delay line; right bottom: plug-in bays

  • Right side. Top left: calibrator; bottom left: plug-in bays; top center: readout board; top right: Z amplifier

    Right side. Top left: calibrator; bottom left: plug-in bays; top center: readout board; top right: Z amplifier

  • Right side detail. Left: calibrator; right: readout.

    Right side detail. Left: calibrator; right: readout.

  • Plug-in backplane board front (left trigger selector piggyback board removed)

    Plug-in backplane board front (left trigger selector piggyback board removed)

  • B Trigger selector piggyback board (A6)

    B Trigger selector piggyback board (A6)

  • Vertical interface piggyback board (A7). The two 155-0095-03 amplifiers (large metal cans) are used to select the signal from one vertical plug-in bay, and drive the delay line.

    Vertical interface piggyback board (A7). The two 155-0095-03 amplifiers (large metal cans) are used to select the signal from one vertical plug-in bay, and drive the delay line.

  • Plug-in backplane board rear

    Plug-in backplane board rear

  • Backplane board sandwich seen from below

    Backplane board sandwich seen from below

  • Horizontal (X) amplifier board (late >B220000)

    Horizontal (X) amplifier board (late >B220000)

  • Vertical (Y) amplifier board

    Vertical (Y) amplifier board

  • Z amplifier board

    Z amplifier board

  • front-panel controls

    front-panel controls

  • 7904 block diagram

    7904 block diagram

  • A 7B92A (B098xxx) displaying a 1.01 GHz sine in HF Sync mode (7904 mainframe, 7A19 amplifier).

    A 7B92A (B098xxx) displaying a 1.01 GHz sine in HF Sync mode (7904 mainframe, 7A19 amplifier).

Power Supply

  • 7904 switchmode power supply, covers removed

    7904 switchmode power supply, covers removed

  • View from right (as seen from front of instrument)

    View from right (as seen from front of instrument)

  • Primary side circuit board

    Primary side circuit board

  • Primary side capacitors

    Primary side capacitors

  • Detail view of transformer from the side

    Detail view of transformer from the side

  • Switching transformer

    Switching transformer

  • Secondary side rectifier board

    Secondary side rectifier board

  • Secondary side post-regulator

    Secondary side post-regulator

  • HV block, multiplier

    HV block, multiplier

Parts

Some Parts Used in the 7904

Part Part Number(s) Class Description Used in
148-0034-00 148-0034-00 Discrete component miniature DPDT relay 5A48 • 7A11 • 7A13 • 7A14 • 7B70 • 7B71 • 7503 • 7904 • 7904A
154-0644-00 154-0644-00 • 154-0644-04 • 154-0644-05 • 154-0644-09 • 154-0893-05 CRT CRT with distributed deflection plates 7704A • 7854 • 7904 • 7904A • R7903
155-0009-00 155-0009-00 Monolithic integrated circuit horizontal lockout logic 7504 • 7514 • 7704 • 7704A • R7704 • 7834 • 7844 • 7854 • 7904 • R7903 • 7904A • 7934 • 7104
155-0010-00 155-0010-00 Monolithic integrated circuit chop divider and blanking 7504 • 7514 • 7704 • R7704 • 7704A • 7834 • 7854 • 7904 • R7903 • 7904A • 7934 • 7104
155-0011-00 155-0011-00 Monolithic integrated circuit clock and chop blanking 485 • 7313 • 7403N • R7403N • 7503 • 7504 • 7514 • 7603 • AN/USM-281C • 7613 • 7623 • 7623A • 7633 • 7704 • R7704 • 7704A • 7834 • 7844 • 7854 • 7904 • 7904A • R7903 • R7912 • 7912AD • 7912HB • 7934 • 7104 • R7103 • AN/USM-281C
155-0012-00 155-0012-00 Monolithic integrated circuit Z Axis Logic 485 • 7504 • 7514 • 7704 • R7704 • 7704A • 7834 • 7844 • 7854 • 7904 • R7903 • 7904A • R7912 • 7934 • 7912AD • 7912HB • 7104 • R7103
155-0013-00 155-0013-00 • 155-0013-01 Monolithic integrated circuit horizontal chop and alt. binary 7504 • 7514 • 7704 • R7704 • 7704A • 7834 • 7854 • 7904 • 7904A • R7903 • 7934 • 7104
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
155-0059-00 155-0059-00 Monolithic integrated circuit HF amplifier 7834 • 7844 • 7854 • 7904 • R7903 • R7912 • 7912AD
155-0060-00 155-0060-00 • 155-0060-01 Monolithic integrated circuit channel selector amplifier R7903 • 7904 • R7912
155-0064-00 155-0064-00 Hybrid integrated circuit vertical output amplifier 7834 • 7854 • 7904 • R7903 • 7912AD • 485 • PG502
155-0065-00 155-0065-00 • 155-0064-01 • 155-0125-00 Hybrid integrated circuit deflection amplifier 7844 • 7904 • R7912 • R7903
155-0067-02 155-0067-00 • 155-0067-02 • 155-0067-03 Monolithic integrated circuit SMPS controller 7704A • 7834 • 7844 • 7854 • 7904 • R7903 • 7904 • 7904A • 7934 • R7912 • 7912AD • 7912HB • 7934 • 7104 • R7103 • 308 • 434 • 485 • 690 • P7001
155-0078-00 155-0078-xx • 155-0273-00 • 155-0274-00 Monolithic integrated circuit broadband amplifier 464 • 465 • 466 • 468 • 475 • 475A • 475M • 485 • 7834 • 7844 • 7854 • 7904 • R7903 • R7912 • 7912AD • 7912HB • 7104 • 7A16A • 7A16P • 7A24 • 7A26 • 7A42 • 067-0587-01 • 067-0680-00 • AM503 • PG502 • PG508 • DC510 • DC5010 • FG5010
155-0095-00 155-0095-00 • 155-0095-01 • 155-0095-03 Hybrid integrated circuit HF differential amplifier 7834 • 7844 • 7904 • R7903 • R7912 • 7912AD
203-0126-90 203-0126-90 Monolithic integrated circuit ft doubler amplifier R7903 • 7904 • 7844

Custom ICs used in the 7000 series readout system

Page Model Part nos Description Designers Used in
155-0014-01 M019D 155-0014-00 • 155-0014-01 analog-to-decimal converter Barrie Gilbert 7000 series readout system • 7854 • 7934 • 7J20 • 7L5 • P7001
155-0015-01 M020F 155-0015-00 • 155-0015-01 analog data switch Barrie Gilbert 7000 series readout system • 7854 • 7934
155-0017-00 M025 155-0017-00 5 MHz decade counter Barrie Gilbert 7000 series readout system • 7854 • 7934
155-0018-00 M026 155-0018-00 zeros logic control Les Larson 7000 series readout system • 7934
155-0019-00 M027 155-0019-00 decimal point and spacing control Les Larson 7000 series readout system
155-0020-00 M028 155-0020-00 output assembler Les Larson 7000 series readout system
155-0021-00 M029C 155-0021-00 • 155-0021-01 timing generator Les Larson 7000 series readout system • 7854 • 7934
155-0023-00 M160 155-0023-00 character generator (0 1 2 3 4 5 6 7 8 9) Barrie Gilbert 7000 series readout system
155-0024-00 M161 155-0024-00 character generator (↓ < I / + - + C Δ >) Barrie Gilbert 7000 series readout system
155-0025-00 M162 155-0025-00 character generator (m μ n p X K M G T R) Barrie Gilbert 7000 series readout system
155-0026-00 M163 155-0026-00 character generator (S V A W H d B c Ω E) Barrie Gilbert 7000 series readout system
155-0027-00 M164 155-0027-00 character generator (U N L Z Y P F J Q D) Barrie Gilbert 7000 series readout system
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