The Tektronix 7844 is a 400 MHz dual-beam CRT oscilloscope that takes two 7000-series vertical plug-ins and two 7000-series horizontal plug-ins.

Tektronix 7844
400 MHz dual-beam non-storage mainframe
Tektronix 7844 Opt.78 (P11 phosphor)

Produced from 1974 to 1988

Manuals
(All manuals in PDF format unless noted otherwise)

Versions include the 7844 bench-top lab scope and R7844 rack-mount model.

Circuit design for the 7844 was done by Chuck Scott, Dick Anderson, Keith Taylor, and Bob White. Project manager for the 7844 was Murlan Kaufman. The 7844's CRT was designed by Conrad Odenthal and Ken Hawken.

A typical configuration might have included 7A19 or 7A24 amplifiers, 7B80/7B85 or 7B92A timebases.

Key Specifications

Bandwidth 400 MHz with 7A19, 7A29 (eq. 0.9 ns rise time), 300 MHz with 7A24
Fastest calibrated sweep 1 ns/Div (with 7B80, 7B85, 7B92A)
Beam isolation > 100:1 from DC to 150 MHz, > 30:1 from 150 MHz to 400 MHz
X-Y Phase Shift < 2° from DC to min. 50 kHz
Horizontal bandwidth DC to at least 1 MHz
Z axis input 2 Vp-p for full intensity range (positive decreases), input impedance 500 Ω, rise time 15  ns, max. 1 MHz
CRT T7840, p/n 154-0713-00 with P31 phosphor, or 154-0713-04 with P11 phosphor (Opt. 78), acceleration 24 kV (−3/+21)
Calibrator 4 mV, 40 mV, 400 mV or 4 V into >100 kΩ, 0.4 mV, 4 mV, 40 mV or 400 mV into 50 Ω; 1 kHz
Power 90-132 V or 180-264 V, 48 to 440 Hz, max. 235 W
Weight 16.3 kg (36 lbs) / R7844: 15 kg (33 lbs)
Options
  • Opt.03 – EMI shielding
  • Opt.21 – Dedicated vertical deflection system (eliminates vertical mode switch and crossover board)
  • Opt.22 – Enhancer (generates raster scan to illuminate the entire CRT at the end of beam 2 sweep)
  • Opt.78 – P11 phosphor

Links

Documents Referencing 7844

Document Class Title Authors Year Links
Tekscope 1974 V6 N4.pdf Article A 400-MHz Dual-Beam Oscilloscope Murlan Kaufman 1974

Patents that may apply to 7844

Page Title Inventors Filing date Grant date Links
Patent US 3819984A Side-by-side dual gun crt having horizontal deflector plates provided with side shields for correction of geometric distortion Ken Hawken 1973-02-12 1974-06-25
Patent US 3921025A Dual-beam CRT with vertical trace bowing correction means Conrad Odenthal 1974-07-05 1975-11-18
Patent US 3983444A Dual beam CRT with inner gun and outer gun shield means for correcting keystone distortion Conrad Odenthal 1975-10-24 1976-09-28

Internals

The 7844's CRT has distributed vertical deflection plates. It uses a number of custom ICs, such as 155-0064-00, 155-0065-00 and 155-0059-00 in the vertical amplifiers, 155-0095-00 in the vertical interface, 155-0078-00 in the trigger selector, and 155-0022-00 in the horizontal interface. The horizontal and Z axis amplifiers are discrete.

The 7844 is more complex than all other 7000 mainframes except the 7854 because vertical and horizontal amplifiers as well as the Z axis control boards exist twice, and there is an extra switching logic board. As a consequence, verifying correct operation requires testing many possible combinations of settings – for example, a defect on the vertical switching board could cause a problem only in the case of both beam 1 and 2 using horizontal bay B, but not if beam 1 used A and beam 2 used B. Moreover, calibration and adjustment is significantly more work than in a single-beam scope, e.g. CRT geometry trimpots need to be adjusted for matching both beams, not only for best geometry, and these adjustments even interact slightly.

The power supply is a resonant switch-mode inverter with linear post-regulation, similar to the one in the 7904. It uses the 155-0067-02 controller. Despite having an SMPS, the 7844 is fairly heavy behause of the duplicate internal components, especially the second vertical delay line. The delay lines need extra space and are located vertically to the right of the CRT instead of below the CRT as in other 7xx4s.

Unlike some other 7000 series mainframes with switchmode PSUs, the 7844 does have a fan.

Early 7844 (SN B109999 and earlier) have issues with horizontal aberrations for sweep rates of 1 ns/Div. After discovery of the issue modification kits (040-0804-00) that replace the horizontal amplifier were offered. For more information see the manual of the 067-0657-00 Normalized Ramp Generator that was use to investigate this issue.

Prices

  Year 1976 1980 1984 1990
(R7844)
Mainframe only Catalog price $6,100 $9,125 $13,435 $19,500
In 2023 dollars $32,600 $33,700 $39,300 $45,400
Mainframe with 2 × 7A19,
7B85, 7B80
Catalog price $9,500 $14,275 $21,520 $30,660
In 2023 dollars $50,800 $52,700 $63,000 $71,300

Pictures

Interior

Option 22

Components

Some Parts Used in the 7844

Part Part Number(s) Class Description Used in
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
155-0011-00 155-0011-00 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
155-0022-00 155-0022-00 155-0022-01 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
155-0065-00 155-0065-00 155-0064-01 155-0125-00 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
1N3182 152-0269-00 Discrete component varactor diode 3L5 1L5 3T7 492 465M 7844 2465
203-0126-90 203-0126-90 Monolithic integrated circuit ft doubler amplifier R7903 7904 7844
T7840 154-0713-00 154-0713-04 CRT dual-beam CRT 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