7904A
The Tektronix 7904A is a 500 MHz, non-storage 7000-series oscilloscope mainframe with four bays, introduced in 1984. It is a redesign of the predecessor model 7904 from 1971, using integrated circuits developed for the 1 GHz 7104.
Key Specifications
| Bandwidth | 500 MHz (with 7A29 or 7A19 amplifier) |
|---|---|
| Fastest calibrated sweep | 500 ps/div with 7B10, 7B15, or 7B92A |
| Outputs | Vertical Signal Out (25 mV/Div into 50 Ω, 0.5 V/Div into 1 MΩ); +Sawtooth; +Gate; camera power; probe power |
| Z axis input | +2 V to blank from max. intensity, –2 V to unblank from min, intensity; 1 MHz BW; 470 Ω // 50 pF; max. 15 V DC+ peak AC |
| CRT |
Acceleration voltage 24 kV (+21 / –3 kV)
|
| Calibrator | 1 kHz square wave, 40 mV to 4 V in decade steps (4/40/400 mV into 50 Ω); 40 mA current loop |
| Power | 90−132 V or 180−250 V, 48−440 Hz, 210 W nom. |
| Weight | 16.9 kg (37.2 lbs) without plugins |
| Dimensions | 34.5 cm × 30.5 cm × 57.7 cm (13.6 in x 12.0 in x 22.7 in) H×W×L |
| Options |
|
Links
- 7904A @ amplifier.cd
- Repairing front panel buttons of Tektronix 7904 oscilloscope
- Tektronix 7904A lab check in and LED MOD by Zenwizard Studios @ YouTube
- Tektronix 7904A Power Supply Repair by Zenwizard Studios @ YouTube
Documents Referencing 7904A
- (no results)
Internals
The signal path is completely differential and the internal signal wiring is 50 Ω coax. The CRT (154-0644-05) has distributed vertical deflection plates.
The 7904A 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.
Differences to 7904
The 7904A borrows heavily from the 1 GHz 7104 introduced in 1978 in terms of front panel layout, mechanical design, and electronics, re-implementing the vertical amplifier using Hypcon-packaged amplifier chips such as the 155-0173-05, 155-0175-05 and 155-0178-05.
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 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 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).
In addition, the 7904A adds a fan in the SMPS.
Prices
| Mainframe only | Mainframe + 7A19 + 7A19 Opt.04 + 7B92 | ||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
|
Pictures
-
7904A
-
7904A Rear
-
7904A Top with Horizontal Amplifier at top right
-
7904A Right with Z-axis on top right and 2nd Gen. Readout board at bottom right
-
7904A Left with Vertical Amplifier (top) and Vertical switch board (bottom)
-
7904A Topleft
-
7904A Closeup of Vertical amplifier
-
7904A Low-voltage Power Supply Schematic
-
7904A Horizontal and vertical amplifiers
-
7904A without rear fan
-
7904A with side-mounted fan
Parts
Some Parts Used in the 7904A