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[[Image:Tek1502-front.JPG|thumb|600px|right|Tektronix 1502 Time Domain Reflectometer]]
{{Instrument Sidebar
|manufacturer=Tektronix
|model=1502
|class=Reflectometer
|series=
|summary=Time Domain Reflectometer
|image=Tek1502-front.JPG
|caption=Tektronix 1502 Time Domain Reflectometer (CRT version)
|introduced=1975
|discontinued=(?)
|designers=Hans Geerling
|manuals=
'''1502'''
* [[Media:070-1790-00.pdf|Tektronix 1502 Operators Manual]]
* [[Media:070-1792-01.pdf|Tektronix 1502 Service Manual -01]]
* [[Media:070-1792-02.pdf|Tektronix 1502 Service Manual -02]]
* High-res 1502 schematics:
** [[Media:1502_Vertical_Amp.pdf|Vertical amp board]]
** [[Media:1502_Schematic_Mainborad_Components.pdf|Main board]]
** [[Media:1502_SCHEMATIC-Output_Amp.png|Output amplifier]]
* [[Media:Tek_1502_Wizard_Workshop.pdf|Tektronix 1502 Wizard Workshop Articles]]
* [[Media:Tek_1502_mods.pdf|Tektronix 1502 Modifications]]


The '''Tektronix 1502''' is a series of Time Domain Reflectometers commonly used to test coaxial
'''1502B'''
cables although they have many other uses. The US military was a major purchaser, most of the
* [[Media:070-6266-01.pdf|Tektronix 1502B Operator Manual]]
first series (the 1502, no letter) will be found surplus with some sort of US military
* [[Media:070-6267-04.pdf|Tektronix 1502B Service Manual]]
property ID tag and an NSN sticker.


The first version used a CRT and is almost completely analog along with some discrete digital
'''1502C'''
logic used to pre-fire and fire the [[tunnel diodes|tunnel diode]] pulser.  The later models (1502B/C)
* [[Media:070-7169-05.pdf|Tektronix 1502C User Manual]]
used an LCD display and a microprocessor.  The other major difference is the line charging method.
* [[Media:070-7168-04.pdf|Tektronix 1502C Service Manual]]
The 1502 uses a fast (36 ps) tunnel diode pulser, the later models used a half sine wave to
charge the line.  The TD pulser, with its Dirac delta edge gives much better short range
sensitivity although it is much easier to destroy.


There are four key parts in the 1502 that make repair difficult.  The original sampling gate
'''Other'''
(CR1732, Tek [[152-0631-00]]) is no longer available, but Avago RF Schottky barrier diodes in
* [[Media:Tektronix_Y-T_chart_recorder.pdf|Tektronix Chart Recorder User/Service Manual]]
the SOT series pair package (HSMS-2822, HSMS-282C) are a close substitute.  These sampling bridges are so small and light that soldering them in place can be a frustrating experience.  The leads are plated steel and if the soldering iron has a magnetic tip (e.g, many Weller models with temperature control), this can cause the gate to be attracted to the iron.  Even with a non-magnetic iron such as a small 15-watt Antex, the surface tension of the solder is enough to cause the gate to "float" away from its intended mounting location when the iron is removed from the molten solder joint.  A special "hold-down" device can be made to hold the bridge in place and was described in a Wizard's Workshop article.  I'll attempt to locate and post that article.


There is a [[snap-off diode]] (CR1632, Tek [[152-0335-01]]) in the sampling gate pulse shaper
* [[Media:070-2178-00.pdf|Watertight Sealing Procedures for 1502/1503 TDRs]]
that is also no longer available but it usually doesn't fail. 
* [[Media:Optimize falltime and aberrations 1502.pdf|Guide to Optimizing Falltime and Aberrations in the 1502]]


The first pulse shaping TD (CR1609, tek [[152-0140-01]], 10 mA, 8 pF) was a fairly common TD
:''Note that the manuals for the 1502B and 1503C are still available from Tektronix.''
and there are [[Russian tunnel diodes|Russian substitutes available]].  The primary fast pulse TD (CR1703, Tek [[152-0489-00]],
}}
21 mA, 1.5 pF) is simply no longer available.  The russian replacement is GI308E, it requires soldering to the original heatsink.
The '''Tektronix 1502''' is a series of Time Domain Reflectometers which replaced the [[1501]] in 1975.  The 1502 is for high resolution, sister model [[1503]] for long range.


If you want to design a replacement, I suggest looking at Analog Devices ADCMP580, and Starecki and Misiaszek's paper,
They are commonly used to test coaxial cables, although they have many other uses.
''[http://www.ise.pw.edu.pl/~tomi/papers/wilga2006_50ps.pdf Low cost programmable pulse generator with very short rise/fall time]''.
The US military was a major purchaser, therefore most of the first series (the 1502, no letter) will be found surplus with some sort of US military property ID tag and an NSN sticker.


There appears to have been an optional "static suppressor" available, Tek 011-0132-00, in a BNC M-F
[[Hans Geerling]] did most of the circuit design on the 1502.
package used to protect the sampler and TD.  It's pretty obscure.  The BNC connector on later 1502s contained an internal shorting bar that shorted the center conductor to the shell with no mating connector installed.  In use, it was to short out the connecting cable so that any static on the line would be discharged before opening up the BNC connector to the internals of the TDR.  Often, this shorting bar would break off rendering the connector unable to discharge a cable to be connected.  Replacing this BNC connector (or any front-panel component, for that matter) is a laborious process involving resealing the front panel for waterproofing.  The original 1502 and 1503 were the first Tektronix instruments to be fully waterproof (with the X-Y Module installed) such that it could actually be operated while submerged to a shallow depth.  The front panel sealing is a very involved process utilizing several different silicone (grease and RTV) products to do the job.  Tektronix produced a separate Instuction Manual specifically for waterproofing details of the 1500-series.


The other common failure is the battery.  The power supply was designed to protect both the instrument
{{MissingSpecs}}
and the battery from abuse, so any failure will cause the power supply to latch up (via Q6547/Q6549)
and the unit will appear dead.  The pack is rebuildable with NiCd battery cells.  To operate without
a battery in place use a 200 to 270 Ω / 10 W power resistor in parallel with a 2200 μF cap (> 25 V); this
will fool the power supply protection circuit into thinking that it's charging a valid battery.


Another common failure is a defective DISTANCE dial.  Operators expect the numerical readout of this dial to go from zero to 999 and it is not designed to do that.  Often, the internal plastic stops get broken from operators forcing the dial past its intended stop, rendering the part useless.
==Internals and version differences==
The first version used a CRT and is an almost completely analog design except for some discrete digital logic used to pre-fire and fire the [[tunnel diodes|tunnel diode]] pulser.   
The later models (1502B/C) used a liquid-crystal display and a Z80 microprocessor.


==Manuals==
The other major difference between versions is the line charging method.
The 1502 uses a fast (36 ps) tunnel diode pulser, the later models used a half sine wave to charge the line. 
The TD pulser, with its Dirac delta edge, gives much better short range sensitivity, although it is much easier to destroy.


* [http://w140.com/TEK-1502-OM-SM-1.pdf Tektronix 1502 Service Manual (PDF)]
==Repair issues==
* [http://w140.com/tek_1502b_service.pdf Tektronix 1502B Service Manual (PDF)]
→ see [[1502/Repairs]]
* [http://w140.com/tek_1502c_service.pdf Tektronix 1502C Service Manual (PDF)]
 
* [http://w140.com/tekwiki/images/2/23/Tektronix_Y-T_chart_recorder.pdf Tektronix Chart Recorder User/Service Manual (PDF)]
==Replacement==
:''Note that the manuals for the 1502B and 1503C are still available from Tektronix.''
MOHR Test and Measurement manufactures a direct replacement to the 1502B and 1502C using an updated version of the same pulser/sampler.
Any procedures or recorded waveforms are repeatable using the MOHR TDR.''[http://www.mohr-engineering.com/ct100 CT100B TDR Cable Analyzer]''.
 
==Links==
{{Documents|Link=1502}}
 
==Prices==
1979: $3,750 (~$14,700 in 2022 Dollars)
 
According to an [[Media:Tek Schottky Diodes Memo rot.pdf|internal memo]], in 1979 annual sales were estimated at 543 units.


==Pictures==
==Pictures==
'''1502'''
<gallery>
Tek1502-top.JPG|Top boards of the 1502
Tek1502-bottom.JPG|Underside of 1502 with stripline sampler and pulser exposed
Tek1502-samplinggate.JPG|Sampling gate near the BNC end of stripline
Tek1502-pulser.JPG|Pulser end of the stripline
Tek1502-td.JPG|Pulser TD removed from stripline
Tek1502-tdcurve.JPG|Pulser TD curve traced with a 576
TEK1502-HV-board-top.jpg|HV board top view
TEK1502-HV-board-bottom.jpg|HV board bottom view
Tek 1502 with printer.jpg|Tek 1502 with printer
Tek 1502 trace no connection.jpg
1502_Front_metric_version.jpg|Tek 1502 Metric Version (Option 5)
</gallery>
'''1502B'''
<gallery>
<gallery>
Image:Tek1502-top.JPG|Top boards of the 1502
Tek 1502b 1.jpg|1502B
Image:Tek1502-bottom.JPG|Underside of 1502 with stripline sampler and pulser exposed
Tek 1502b 2.jpg|1502B
Image:Tek1502-samplinggate.JPG|Sampling gate near the BNC end of stripline
Tek 1502b 3.jpg|1502B
Image:Tek1502-pulser.JPG|Pulser end of the stripline
Tek 1502b 4.jpg|1502B
Image:Tek1502-td.JPG|Pulser TD removed from stripline
Image:Tek1502-tdcurve.JPG|Pulser TD curve traced with a 576
File:Tek 1502 with printer.jpg|Tek 1502 with printer
</gallery>
</gallery>




[[Category:Time-domain reflectometers]]
[[Category:Time-domain reflectometers]]
[[Category:Introduced in 1976]]

Latest revision as of 04:58, 11 March 2024

Tektronix 1502
Time Domain Reflectometer
Tektronix 1502 Time Domain Reflectometer (CRT version)

Produced from 1975 to (?)

Manuals
Manuals – Specifications – Links – Pictures

The Tektronix 1502 is a series of Time Domain Reflectometers which replaced the 1501 in 1975. The 1502 is for high resolution, sister model 1503 for long range.

They are commonly used to test coaxial cables, although they have many other uses. The US military was a major purchaser, therefore most of the first series (the 1502, no letter) will be found surplus with some sort of US military property ID tag and an NSN sticker.

Hans Geerling did most of the circuit design on the 1502.

Key Specifications

  • please add

Internals and version differences

The first version used a CRT and is an almost completely analog design except for some discrete digital logic used to pre-fire and fire the tunnel diode pulser. The later models (1502B/C) used a liquid-crystal display and a Z80 microprocessor.

The other major difference between versions is the line charging method. The 1502 uses a fast (36 ps) tunnel diode pulser, the later models used a half sine wave to charge the line. The TD pulser, with its Dirac delta edge, gives much better short range sensitivity, although it is much easier to destroy.

Repair issues

→ see 1502/Repairs

Replacement

MOHR Test and Measurement manufactures a direct replacement to the 1502B and 1502C using an updated version of the same pulser/sampler. Any procedures or recorded waveforms are repeatable using the MOHR TDR.CT100B TDR Cable Analyzer.

Links

Documents Referencing 1502

Document Class Title Authors Year Links
Tekscope 1975 V7 N2.pdf Article Two Weatherproof TDR Cable Testers for Field Use Ivan Ivanov 1975 1502 • 1503
Tekscope 1975 V7 N3.pdf Article New Products 1975 5444 • 1502 • 1503 • 455 • E4010 • E4010-1 • 4923 • 2701 • 2703 • J6523 • WP1205
TekWeek (partial) October 10, 1975.pdf Article Spectrum analyzers require high technology Thor Hallen • Dave Friedley 1975 Spectrum Analyzers • Pentrix • 7L5 • 5L4 • 7L12 • 7L13 • 1401 • 491 • 1405 • 1502 • 1503

Prices

1979: $3,750 (~$14,700 in 2022 Dollars)

According to an internal memo, in 1979 annual sales were estimated at 543 units.

Pictures

1502

  • Top boards of the 1502

    Top boards of the 1502

  • Underside of 1502 with stripline sampler and pulser exposed

    Underside of 1502 with stripline sampler and pulser exposed

  • Sampling gate near the BNC end of stripline

    Sampling gate near the BNC end of stripline

  • Pulser end of the stripline

    Pulser end of the stripline

  • Pulser TD removed from stripline

    Pulser TD removed from stripline

  • Pulser TD curve traced with a 576

    Pulser TD curve traced with a 576

  • HV board top view

    HV board top view

  • HV board bottom view

    HV board bottom view

  • Tek 1502 with printer

    Tek 1502 with printer

  • Tek 1502 Metric Version (Option 5)

    Tek 1502 Metric Version (Option 5)

1502B

  • 1502B

    1502B

  • 1502B

    1502B

  • 1502B

    1502B

  • 1502B

    1502B

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