7904: Difference between revisions

Latest revision as of 04:37, 26 September 2024

Tektronix 7904

500 MHz non-storage mainframe

Produced from 1971 to 1984

Manuals

7904

Tektronix 7904 Operators Manual
Tektronix 7904 Instruction Manual with PSU Schematics SN B260000+ (OCR)
Tektronix 7904 Instruction Manual with complete schematics Below SNB260000 (Needs OCR)
Servicing the 7904 High-Efficiency Power Supply
Horizontal Amplifier SN B010100 - B079999

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 V_p-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

7904 Repair with Video
Tek 7904 @ amplifier.cd
Repairing front panel buttons of Tektronix 7904 oscilloscope

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 "f_t 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
Mainframe only	In 2024 Dollars	$21,800	$22,600	$23,900
Mainframe with 7A19, 7A19 Opt. 04, 7B92	Catalog price	$5,500	$7,765	$12,015
Mainframe with 7A19, 7A19 Opt. 04, 7B92	In 2024 Dollars	$41,300	$42,900	$45,800

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 Tektronix New Products 1972 brochure.

Pictures

7904 (non-A) front
7904 rear
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 detail. Left: calibrator; right: readout.
Plug-in backplane board front (left trigger selector piggyback board removed)
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.
Plug-in backplane board rear
Backplane board sandwich seen from below
Horizontal (X) amplifier board (late >B220000)
Vertical (Y) amplifier board
Z amplifier board
front-panel controls
7904 block diagram
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
View from right (as seen from front of instrument)
Primary side circuit board
Primary side capacitors
Detail view of transformer from the side
Switching transformer
Secondary side rectifier board
Secondary side post-regulator
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

@@ Line 2: / Line 2: @@
 |manufacturer=Tektronix
 |series=7000-series scopes
-|model= 7904
+|model=7904
 |designers=Val Garuts;Thor Hallen;John McCormick;Les Larson;Bill DeVey;Bill Peek;Hans Springer;Joe Burger;Joel Swanno;Ken Hawken
 |image=Tek-7904-front.jpg
 |caption=Tektronix 7904 (with [[7A19]], [[7A11]], [[7D11]], [[7B85]])
 |introduced=1971
-|discontinued=1990
+|discontinued=1984
 |summary=500 MHz non-storage mainframe
 |manuals=
 '''7904'''
 * [[Media:070-1399-00.pdf|Tektronix 7904 Operators Manual]]
-* [[Media:070-2390-00.pdf|Tektronix 7904 Instruction Manual]] SN B260000+ (OCR)
+* [[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]]
-'''7904A'''
-* [[Media:070-4593-00.pdf|Tektronix 7904A Manual, May 1989 Revision]] (OCR, low quality scan, whole schematics)
-* [[Media:070-4593-00 hires split schematics.pdf|Tektronix 7904A Manual, May 1989 Revision]] (OCR, good quality scan, split schematics)
 <small>
-'''Alternate Copies'''
-* [https://bama.edebris.com/download/tek/7904/Tektronix_7904_Service_May1983.pdf Tektronix 7904 Manual May 1983] @ BAMA
 '''Modifications'''
 * [https://hakanh.com/dl/docs/kitinstructions/050-0650-00.pdf 050-0650-00 (1980) Vertical amplifier IC replacement]
@@ Line 35: / Line 31: @@
 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 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.
@@ Line 46: / Line 42: @@
 {{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 | 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; <br />7904A: 4 mV to 4 V (p-p) in decade steps, 1 kHz; 40 mV to 400 mV into 50 Ω }}
+{{Spec | Inputs | Z Axis (15 V<sub>p-p</sub>) }}
-{{Spec | Power consumption | 190 W }}
-{{Spec | Weight | 13.5 kg (30 lbs) }}
 {{Spec | CRT |
-* Standard: (8×10 Div @ 1 cm), P31 (green) [[154-0644-05]] or P11 (blue) [[154-0644-09]]
+* 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]]
+}}
+{{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. }}
+{{Spec | Weight | 13.5 kg (30 lbs) }}
+{{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|
+* 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
 }}
 {{EndSpecs}}
 ==Links==
-* [[Media:A subnanosecond realtime oscilloscope garuts hallen.pdf|A Subnanosecond Realtime Oscilloscope]], [[Media:Tekscope 1971 V3 N4 Jul 1971.pdf | Tekscope Vol.3 No.4, July 1971]]
 * [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] / [http://amplifier.cd/Test_Equipment/Tektronix/Tektronix_7000_series_mainframe/7904A.htm 7904A] @ amplifier.cd
+* [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]
-* [http://www.barrytech.com/tektronix/tek7000/tek7904.html Tek 7904] / [http://www.barrytech.com/tektronix/tek7000/tek7904a.html 7904A] @ barrytech.com*
-* [https://www.youtube.com/watch?v=GQn0EqW-u74 Tektronix 7904 lab check in and LED MOD] by Zenwizard Studios @ YouTube
 {{Documents|Link=7904}}
-{{Documents|Link=7904A}}
+{{PatentLinks|7904}}
-===7904A differences===
-The 7904A ([[:Category:Introduced in 1984 |introduced in 1984]]) borrows heavily from the previously introduced [[7104]] in terms of front panel layout, mechanical design, and electronics, re-implementing the vertical amplifier using Hypcon-packaged amplifier chips such as the [[155-0178-00]].
-The 7904 had the elaborate 5-decade built-in calibrator with variable rate that was common on all first-generation 4-bay [[7000-series scopes]], it was dropped from the 7904A. The [[7000-series remote control connector|rear remote control connector]] unique to early 7000-series scopes was dropped as well.
-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).
-===Options===
-<div style="column-count:4;-moz-column-count:4;-webkit-column-count:4">
-* 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
-</div>
 ==Operation==
@@ Line 100: / Line 84: @@
 ==Internals==
-The 7904(A) incorporates a 65 ns Y delay line.
+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.
-This delay is too short for some older time bases such as [[7B53]] to display the trigger event. 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]].
-===7904===
-The 7904 uses a switch-mode power supply and has no fan.
 [[Thor Hallen]] designed the main vertical amplifier and the [[7A19]] plugin (Note 1).
@@ Line 137: / Line 119: @@
 |−
 |}
-===7904A===
-The 7904A is a complete redesign and uses the [[155-0173-05]], [[155-0175-05]] and [[155-0178-05]] amplifiers developed for the [[7104]]. A fan is added at the rear switch mode power supply.
 ==Prices==
@@ Line 149: / Line 128: @@
 ! 1976
 ! 1980
-! 1984
-! 1990
 |-
 ! Model
@@ Line 157: / Line 134: @@
 |align=center| 7904
 |align=center| 7904
-|align=center| 7904A
-|align=center| 7904A
 |-
 !rowspan=2| Mainframe only
@@ Line 165: / Line 140: @@
 |align=right|  $4,100
 |align=right|  $6,265
-|align=right|  $8,810
-|align=right| $12,750
 |-
-! In 2022 Dollars
+! In 2024 Dollars
-|align=right| $19,500
+|align=right| $21,800
-|align=right| $20,300
+|align=right| $22,600
-|align=right| $21,400
+|align=right| $23,900
-|align=right| $23,800
-|align=right| $27,400
 |-
 !rowspan=2| Mainframe with [[7A19]],<br />7A19 Opt. 04, [[7B92]]
@@ Line 180: / Line 151: @@
 |align=right|  $7,765
 |align=right| $12,015
-|align=right| $17,425
-|align=right| $24,190
 |-
-! In 2022 Dollars
+! In 2024 Dollars
-|align=right| $37,000
+|align=right| $41,300
-|align=right| $38,400
+|align=right| $42,900
-|align=right| $41,000
+|align=right| $45,800
-|align=right| $47,200
-|align=right| $52,000
 |}
 ==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==
-===7904 non-A===
 <gallery>
 Tek-7904-front.jpg | 7904  (non-A) front
@@ Line 214: / Line 180: @@
 _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====
 <gallery>
@@ Line 227: / Line 193: @@
 -psu-regulator.jpg    | Secondary side post-regulator
 Tek_7904_SMPS-HV-Block.jpeg| HV block, multiplier
-</gallery>
-===7904A===
-<gallery>
-a-front.jpg |7904A
-A_rear.jpg |7904A Rear
-A_top1.jpg |7904A Top with Horizontal Amplifier at top right
-A_right1.jpg |7904A Right with Z-axis on top right and 2nd Gen. Readout board at bottom right
-A_left1.jpg |7904A Left with Vertical Amplifier (top) and Vertical switch board (bottom)
-A_topleft1.jpg |7904A Topleft
-A_left_closeup.jpg |7904A Closeup of Vertical amplifier
-a lvps1.png|7904A Low-voltage Power Supply Schematic
-a-h-v.jpg | 7904A Horizontal and vertical amplifiers
 </gallery>
 ==Parts==
 {{Parts|7904}}
-{{Parts|7904A}}
 {{Custom ICs|7000 series readout system}}
 [[Category:7000 series non-storage mainframes]]