7904: Difference between revisions

Revision as of 03:36, 6 October 2014

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500 MHz non-storage mainframe Tektronix 7904 (with 7A19, 7A11, 7D11, 7B85) Produced from 1971 to 1990 Manuals Tektronix 7904 Manual (PDF) Tektronix 7904A Manual (DjVu) Tektronix 7904A Manual (Shannon Hill PDF with OCR) Tektronix 7904 Manual (Shannon Hill PDF with OCR) Servicing the 7904 High-Efficiency Power Supply (PDF) (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. It was introduced in late 1971/early 1972 (Note 1). The successor model 7904A was introduced in 1974. 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.

7904A differences

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 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).

Specifications

Key Specifications

Bandwidth	500 MHz
Fastest calibrated sweep	500 ps/Div (with 7B92A, other time bases "uncalibrated for first 60 ns")
Acceleration voltage	24 kV
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
Calibrator (7904A)	4 mV to 4 V (p-p) in decade steps, 1 kHz; 40 mV to 400 mV into 50 Ω
Power consumption	190 W
Weight	13.5 kg (30 lbs)
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

Operation

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).

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 makes extensive use of custom integrated circuits and hybrid circuits. 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.

Prices

1990: $12,750 (7904A) = $22,390 @ 2013 value

Links

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

7904 (non-A) front
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 interface board front (left piggyback board removed)
Plug-in interface board rear
Horizontal (X) amplifier board
Vertical (Y) amplifier board
Z amplifier board
front-panel controls
7904 block diagram

7904A

7904A

@@ Line 2: / Line 2: @@
 title=Tektronix 7904|
 image=Tek-7904-front.jpg |
-caption=Tektronix 7904 |
+caption=Tektronix 7904 (with [[7A19]], [[7A11]], [[7D11]], [[7B85]]) |
 introduced=1971 |
 discontinued=1990 |
@@ Line 29: / Line 29: @@
 {{Spec | Power consumption | 190 W }}
 {{Spec | Weight | 13.5 kg (30 lbs) }}
-{{EndSpecs}}
+{{Spec | CRT Options |
-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]]
+}}
+{{EndSpecs}}
 ==Operation==
@@ Line 47: / Line 47: @@
 ==Prices==
-: $12,750 (7904A)
+: $12,750 (7904A) = $22,390 @ 2013 value
 ==Links==
@@ Line 65: / Line 65: @@
 File: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
-File:7904-right.jpg | Right side. Left top: calibrator; left bottom: plug-in bays; center top: readout board; right top: Z amplifier
+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
 File:7904-right-front.jpg | Right side detail. Left: calibrator; right: readout.
 File:7904 interface 1.jpg|Plug-in interface board front (left piggyback board removed)