From TekWiki
(Redirected from 7L5 Opt.25)
Jump to navigation Jump to search
Tektronix 7L5
5 MHz Spectrum Analyzer
Tektronix 7L5

Compatible with 7000-series scopes

Produced from 1976 to 1989

Manuals – Specifications – Links – Pictures

The Tektronix 7L5 is a low frequency (10 Hz – 5 MHz) spectrum analyzer plug-in for 7000-series scopes. It has built-in digital storage, so it will work fine in non-storage mainframes such as the large-screen 7603. It also features digital scale and marker level/frequency (6 digits) readout, and a "max hold" function.

According to the 070-2184-01 manual, instruments with a serial number below Β070000 are missing the B − (Save A) feature and the corresponding button on the front panel. The military version is called PL-1391/U and is also lacking the B − (Save A) feature.

Fendall Winston was Project Leader for the 7L5 and along with Craig Bryant and Steve Morton provided much of the electrical design. Bill Benedict and Don Kirkpatrick did the digital circuitry. Steve Skidmore coordinated mechanical design, with Carlos Beeck doing the optoelectronic switch-in-a-knob. Morris Engelson provided overall engineering direction for the program.

Key Specifications

Input frequency 10 Hz – 5 MHz
Drift < 5 Hz/h
Resolution bandwidth 10 Hz – 30 kHz in ×3 / ×10 steps
Sweep rate 10 s/Div to 0.1 ms/Div in 1−2−5 sequence plus Auto
Residual FM < 40 Hzp-p (< 1 Hz from 50 Hz/Div to 2 kHz/Div)
Outputs Horizontal, Video, Calibrator
Input impedance
  • L1 input module: 50 Ω
  • L2 input module: 75 Ω
  • L3 input module: 50 Ω, 600 Ω or 1 MΩ selectable (75 Ω, 600 Ω or 1 MΩ for the L3-1)
Log Sweep Option 250 Hz to 222.25 kHz by digitally combining three decade sweeps (250 Hz—2.25 kHz, 2.25 kHz—22.25 kHz, 22.25 kHz—222.25 kHz), 2.5 s sweep time


No. Log sweep display Tracking generator LED Readout


Documents Referencing 7L5

Document Class Title Authors Year Links
Tekscope 1975 V7 N3.pdf Article A 5 MHz Digitally-Controlled Spectrum Analyzer 1975
TekWeek (partial) October 10, 1975.pdf Article Spectrum analyzers require high technology Thor Hallen Dave Friedley 1975
AX-3535.pdf Application Note Crystal Device Measurements Using the Spectrum Analyzer Morris Engelson 1977
Tekscope 1977 V9 N3.pdf Article Digital Storage for a Microwave Spectrum Analyzer Dennis Smith Don Kirkpatrick 1977
Tekscope 1977 V9 N2.pdf Article Measuring Harmonic Distortion with a Spectrum Analyzer Ken Matheson 1977
Tekscope 1978 V10 N3.pdf Article Spectrum Analyzer Applications in Baseband Measurements Morris Engelson 1978
AX-3406-1.pdf Application Note EMI Applications Using the Spectrum Analyzer Morris Engelson 1979

In TekWeek 10 Oct 1975, Thor Hallen says

What is the Communications division doing to improve the reliability and field failure rates of high technology instruments such as the 7L5, 7L12 and 7L13 spectrumanalyzers?

Glad you asked! High technology instruments such as the spectrum analyzers you mentioned pose enormous problems in maintaining Tektronix standards for high reliability. Let’s consider the 7L5 for example. The 7L5 is the newest and most dense analyzer to date. It has approximately 2200 electrical parts packed into a two wide plug-in. (The 7L12 and 7L13 are slightly less dense.) With such a high parts population, a 0.5%/year failure rate for individual parts would be disastrous.

In order to deliver better reliability, extraordinary steps are being implemented within the manufacturing area. All benches have been covered with “pink poly” to make a static-free environment for the sensitive Metal Oxide Semiconductor (MOS) circuits of the 7L5. Assemblers and technicians are being trained in static handling of these devices.

The most embarrassing reliability problem that can occur is when the customer has an instrument failure within the first few hours of operation. To prevent this, the 7L5 goes through an extensive 7 day cycled burn-in. Each day the instrument is checked for electrical performance. Any failures are repaired and the burn-in is continued until the instrument has completed the 7 days. Any failures in the last two days will cause the burn-in to continue until the instrument displays two consecutive days without a failure.

Along with burn-in and special handling, extensive effort is given to analysis of field and plant failures for reliability problems.

In answer to your question, we have only discussed the 7L5, but the 7L12 and 7L13 receive similar treatment. There is no final solution to improved reliability. As instruments increase in complexity and reliability, challenge increases proportionately.


Year 1976 1980 1988
Catalog price $4,500 $7,075 $12,500
In 2023 Dollars $24,300 $26,400 $32,400

According to an internal memo, in 1979 annual sales were estimated at 454 units.


7L5 Opt.25 tracking generator plug-in

For internal pictures see the repair section.


Some Parts Used in the 7L5

Part Part Number(s) Class Description Used in
151-0261-00 151-0261-00 Discrete component dual PNP transistor AM501 AM502 CG5001 CG551AP FG501 FG502 FG503 OF150 OF151 OF152 OF235 OS261 RM502A R1140 R5030 R5031 R7912 067-0679-00 067-0807-00 1101 1140A 1141 1142 1350 145 1450 1480 1481 1482 1485 1501 1801 1900 1910 1980 213 26A1 26A2 2620 285 3A9 3A10 3S1 3S2 3S5 3S6 432 434 4501 454 4601 4602 4610 4612 4620 4632 4634 4701 475 492 492A 492AP 494 494P 496 496P 5A13N 5A20N 5A21N 5A22N 5A26 5L4N 502A 5030 5031 576 690SR 7A22 7A29 7B51 7B71 7J20 7L5 7S11 7S12 7912AD
155-0014-01 155-0014-00 155-0014-01 Monolithic integrated circuit A/D converter 7000 series readout system 7854 7934 7J20 7L5 P7001
155-0035-00 155-0035-00 155-0116-00 Monolithic integrated circuit quad op-amp 3110 3S7 3T7 492 492A 492AP 492P 494 494P 496 496P 4010 4011 4012 4013 7L5 7L12 7L13 7L14 7L18 7S11 7T11 7S12 S-6 1461 4602 P7001 613 653
155-0056-00 155-0056-00 155-0056-01 Monolithic integrated circuit sweep control 26G1 26G2 26G3 314 4701 5B10N 5B12N 5S14N 7L5 7L12 7L13 7L14 7L18 7S14 5S14N RG501 Telequipment D63 Telequipment DM63
155-0108-00 155-0108-00 Monolithic integrated circuit operational amplifier 7L5
155-0110-00 155-0110-00 Monolithic integrated circuit custom legend generator 7L5
155-0117-00 155-0117-00 Monolithic integrated circuit readout control 7L5
155-0118-00 155-0118-00 Monolithic integrated circuit vertical control 7L5
155-0157-00 155-0157-00 Monolithic integrated circuit digital storage vertical control 7L5 7L14 7L18 491 492 492A 492BP 492PGM 494 494A 495 496 497P
155-0158-00 155-0158-00 Monolithic integrated circuit digital storage horizontal control 7L5 7L14 7L18 491 492 492A 492BP 492PGM 494 494A 495 496 497P
155-0198-00 155-0198-00 Monolithic integrated circuit readout control 7L5
155-0199-00 155-0199-00 Monolithic integrated circuit vertical control 7L5
VTL2C4 307-0476-00 Discrete component LED-LDR optocoupler 7L5