7104

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Tektronix 7104
1 GHz non-storage mainframe
Tektronix 7104, front view

Produced from 1978 to 1990

Manuals
Manuals – Specifications – Links – Pictures

The Tektronix 7104 is a 1 GHz, non-storage 7000-series oscilloscope mainframe that takes two 7000-series vertical plug-ins and two 7000-series horizontal plug-ins. It was introduced in 1978. There is also a rack-mount version, the R7103, albeit with only one horizontal bay.

The scope employs a micro-channel plate (MCP) CRT design to get good screen intensity at high sweep speeds with moderate acceleration voltage.

The high speed necessitated using distributed deflection plates also for the horizontal deflection system, which reaches a bandwidth of 350 MHz. Option 2 adds a horizontal delay line to make the high horizontal bandwidth available for X-Y mode at a phase shift of <2° up to 50 MHz, nullable at any frequency up to 250 MHz.

The 7A29 1 GHz vertical amplifier and the 7B15/7B10 time base pair were introduced along with the 7104 to match the system bandwidth.

Specifications

Bandwidth 1 GHz (with 7A29) – rise time < 350 ps
Fastest calibrated sweep 200 ps/Div (with 7B10)
Calibrator 40 mV to 4 V (p-p) in decade steps, 1 kHz; 4 mV to 400 mV into 50 Ω; 40 mA with adapter
Y delay line 51 ns (frequency compensated coax pair)
X-Y phase shift
  • base model: < 2° from DC to 50 kHz
  • Opt. 2: < 2° from DC to 50 MHz (with a pair of 7A19 or 7A29, at least one of which has the variable delay option)
Acceleration voltage 12.5 kV
CRT T7100-31-2 Micro channel plate CRT (154-0783-00), P31 phosphor, 8 × 10 Div. @ 8.5 mm, resolution 17 lines / Div., vertical 2 GHz bandwidth @ 1 V/Div sensitivity
Power consumption 215 W
Dimensions 345 mm (h) × 305 mm (w) × 592 mm (l)
Weight 19.8 kg (43.6 lb)
Features
  • Readout
  • 2 probe power connectors

MCP protection

The Micro Channel Plate's amplification degrades irreversibly with operation, in proportion to the log of total charge passed per channel or display area. For this reason, continued operation with a steady trace and especially at large beam currents must be avoided. The 7104 contains a "limited viewing time" circuit to assist with observing this restriction. At beam currents above 0.2 μA, a yellow indicator illuminates, and the beam will be shut down after 20 minutes. The limit time drops to two minutes at an average beam current of 2 μA, and also limits the average current to that value. Single-shot display current is not affected. Despite this limiter, older instruments often exhibit darkening of the screen around the horizontal center line to some degree (see screen shot).

Internals

The 7104 makes extensive use of custom integrated circuits and hybrid circuits, inter alia, the 155-0174-00 Delay Line Compensator, 155-0173-00 Vertical Channel Switch, 155-0176-00 Vertical Output Amplifier, 155-0194-00/01/02/03 CRT Termination, 155-0175-00 Trigger Amplifier, 155-0178-00 Horizontal Output Amplifier, 155-0012-00 Z-Axis controller/amplifier, and 155-0067-02 SMPS controller. The high-speed amplifiers use Hypcon ceramic packages that use elastomer-based frames for coupling chip connections to the circuit board at constant impedance. The signal connections are differential throughout, and the signal path was optimized for matching and low reflection, including the plugin to mainframe card-edge connectors and the use of stripline and coplanar waveguide techniques right up to the CRT.

The 7104's amplifiers use a then novel scheme of "feed-beside" compensation (US Pat. 4.132.958) where instead of matching the HF response to the LF response, the LF response is determined by off-the-shelf operational amplifiers in parallel to the high-speed amplifiers, with a number of adjustable R-C time constants to compensate for thermal and other LF effects. The same technique is employed in the 7A29 amplifier plug-in.

Power Supply

The 7104 uses a switch-mode power supply.

Module A23 (schematic page <14>) contains the mains rectifier, base drive circuitry, and power transistors of the inverter (aka, switcher). These transistors produce a 25 kHz waveform that is fed to the primary of T1310, whose secondaries provide the power for the rest of the scope.

Module A24 (also on schematic page <14>) contains the inverter control circuit and rectifiers for the secondaries of T1310. The inverter control circuit uses the 155-0067-02 inverter control IC, which is U1275.

Module A25 (schematic page <15>) contains the low-voltage regulators. There are independently regulated and current-limited sections for the -50 V, -15 V, +5 V, +15 V and +50 V rails. Each section has an opamp and a BJT output transistor in emitter-follower configuration.

The opamps need power, too. To avoid a dependency cycle, the power supplies for the opamps are separate low-current, low-efficiency zener clamps that in no way depend on the -50 V, -15 V, +5 V, +15 V or +50 V regulators. The power supplies for the opamps produce -22 V, -5.6 V, +5.6 V, and +22 V. To avoid exceeding the opamps' limit of 30 V total rail voltage, each opamp either gets -22 V and +5.6 V, or -5.6 V and +22 V, depending on whether it needs more output swing in the positive or negative direction.

The +50 V section is produces the reference voltage for the other sections. It uses a 9V zener diode, VR1412, as a reference.

The dependency relationship of the supplies is:

  • The -50 V, -15 V, +5, and +15 V sections depend on
    • the +50 V supply for reference voltage,
    • the opamp supplies for to power their opamps, and
    • the A24 semi-regulated rectifier outputs
  • The +50 V depends on
    • the opamp supplies (+22 V and -5.6 V) for to power its opamp,
    • the A24 semi-regulated rectifier outputs (-54 and +54 V)
  • The opamps supplies depend on
    • the A24 semi-regulated rectifier outputs
  • The semi-regulated rectifier outputs depend only on mains power to enter tick/burst mode. However, to enter normal mode, a variety of things need to be working properly.

Prices

  Year 1980 1984 1990
Mainframe only Catalog price $14,400 $21,380 $29,995
2015 value $41,560 $48,930 $54,580
Mainframe with 7A29,
7A29 Opt. 04, 7B15, 7B10
Catalog price $21,730 $31,875 $44,510
2015 value $62,700 $72,960 $88,990

Links

Pictures

Measurements