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The Tektronix 321 is a very compact single-trace,  
{{Oscilloscope Sidebar |
single-timebase portable oscilloscope  
title=Tektronix 321 |
that is almost completely solid state.   
summary=Portable single channel scope |
image=Tek 321 trace.jpg|321 front view |
caption=Tek 321 front |
introduced=1960 |
discontinued=1972 |
manuals=
*[[Media:070-196.pdf|Tektronix 321 Manual]]
*[http://bama.edebris.com/manuals/tek/321a/ Tektronix 321A manual]
*[http://w140.com/tek_070-0425-01_type_321a_sn_100-5999_ocr.pdf Tektronix 321A Manual sn 100 to 5999 (PDF, OCR)]
*[http://w140.com/tek_fcp/tek_type_321_factory_cal_proc.pdf Tektronix 321 factory calibration procedure]
*[[Media:Tek 321 irb.pdf|Tektronix 321 Instrument Reference Book (PDF, OCR)]]
*Needed: 321A SN 6000 up
 
* [[Media:070-425.pdf|Tektronix 321A Manual (PDF, OCR, bad-OCR)]]
* [[Media:tek_321_fcp.pdf|Tektronix 321 factory calibration procedure (PDF, OCR, bad-OCR)]]
* [[Media:Tek 321a fcp june 1968.pdf]]
}}
The '''Tektronix 321''' is a very compact single-trace, single-timebase portable oscilloscope that is almost completely solid state.   
It was [[introduced in 1960|introduced on April 8th, 1960]].
It was [[introduced in 1960|introduced on April 8th, 1960]].
The 321 includes several germanium bipolar transistors,
which are a known reliability problem. 
The 321A was [[introduced in 1964]].
The 321 and 321A have slightly different circuits. 
Early instances of the 321 (sn pre-720) use a
[[5718]] peanut tube as the front-end cathode follower. 
Later 321 and 321A use a [[7586]] Nuvistor for that role. Latest 321A use a FET [[151-1011-01]].
In several circuits, the 321 uses [[OC170]] transistors
where the 321A uses [[2N2207]] transistors. 


[http://elektrotanya.com/tektronix_321.pdf/download.html Tektronix 321 Manual]
The 321 includes several germanium bipolar transistors, which are a known reliability problem. 
 
The '''321A''' was [[introduced in 1964]].  The 321 and 321A have slightly different circuits.
Early instances of the 321 (sn pre-720) use a [[5718]] peanut tube as the front-end cathode follower. 
 
Later 321 and 321A use a [[7586]] Nuvistor for that role. Latest 321A (SN6000 up) use a FET [[151-1011-01]].
In several circuits, the 321 uses [[OC170]] transistors where the 321A uses [[2N2207]] transistors. 


[http://bama.edebris.com/manuals/tek/321a/ Tektronix 321A manual]
{{BeginSpecs}}
{{Spec | Bandwidth      | 5 MHz (321) / 6 MHz (321A)  }}
{{Spec | Rise time      | 70 ns (321) / 64 ns (321A)  }}
{{Spec | Sweep          | 0.5 μs/Div to 0.5 s/Div, 1—2—5, ×5 magnifier (i.e. to 50 ns/Div) }}
{{Spec | Deflection      | 10 mV/Div to 20 V/Div }}
{{Spec | Input impedance | 1 MΩ // 35 pF }}
{{Spec | Calibrator      | 0.5 V<sub>p-p</sub>, about 2 kHz  }}
{{Spec | CRT            | [[T3210]] or [[154-433|T3211-31]] or [[154-433]], P31 phosphor, 10 × 6 Div. @ 6.25 mm (0.25"), 4 kV acceleration }}
{{Spec | AC Power        | 90—136 V or 180—272 V, 20 W }}
{{Spec | DC Power        | 11.5—35 V, 8.5 W min., 24.5 W max., 700 mA current typ. }}
{{Spec | Battery        | Ten size "D" NiCd cells, runtime 5 h (4 Ah cells), 3 h (2.5 Ah cells), charge time 16 h }}
{{Spec | Dimensions      | 21.67 cm × 14.6 cm × 40 cm (8.5" × 5.75" × 16") }}
{{Spec | Weight          | unknown, about 5 kg }}
{{Spec | Features |
* Ext Trig / X input (supports X-Y displays)
* External blanking input (Z modulation)
* Built-in battery
}}
{{EndSpecs}}
==External Power Connector==
Douglas W Jones wrote:
<blockquote>
I've got a Tektronix 321 scope (serial number 001917) that I need to run from an external
DC supply.  The problem is, I have only the line cord, and not the
DC cord.  The power input plugs on the scope are obviously
custom, long predating the standard IEC plug everyone uses today.


[http://w140.com/tek_fcp/tek_type_321_factory_cal_proc.pdf Tektronix 321 factory calibration procedure]
So I improvised.  The pin spacing for the 3-pin DC input plug is
very close to the spacing of Molex 6, 9 and 12-pin plugs, and the
pin diameter is not too much larger than Molex uses.  So, I
picked up a 6-pin Molex housing and 3 female molex pins, and
then cut the housing down to 4 pins (using my pocket knife).
 
I used an old IEC cord for the DC input wires, with the plugs cut
off both ends.  I attached the wires on one end to the molex pins
and pushed them into the housing, then jammed to housing down
onto the Tektronix connector (this flared the female Molex pins
to fit the Tektronix pins.  The other end of the DC power cord got
banana plugs to fit the output posts of my DC power supply.
 
The net result works fine, plugs and unplugs nicely, and unlike
other power supply solutions I've seen, involves no changes to
the scope.
</blockquote>
<div style="padding-left: 3em;"><gallery>
Dwj tek 321 ps connector.jpg|321 External Power Connector
Dwj tek 321 ps cable.jpg|Douglas W Jones' 321 External Power Cable
</gallery></div>
<blockquote>
Added note:  My bench supply has an analog Ammeter on it.
The starting surge of the 321 is about 1.5 amps, perhaps 2,
tapering down to 0.7 amps in under a second.  It seems to draw
a steady 0.7A regardless of what you're doing with it.  The
current drain doesn't change when you vary the supply from 12 to
18V — this is because the 321 uses a linear regulator.
</blockquote>
==Links==
* [https://sites.google.com/site/johnengsdeadtechrescue/photos/john-s-ideas-to-restore-dead-technology/repair-challenge-tektronix-321-oscilloscope--the-first-transistor-oscilloscope Repair Challenge Tektronix 321 Oscilloscope]
==Pictures==


<gallery>
<gallery>
Image:321_front.jpg|321 front view
tek-321-front.jpg | 321 rectangular front
Image:321_right_case.jpg|321 right case
tek-321-round-front.jpg | 321 round front
Image:321_left_internal.jpg|321 left internal
tek-321-round-vs-rect.jpg | 321 round vs. rectangular models
Image:321_right_internal.jpg|321 right internal
321_pair.JPG | 321 and 321A
Image:321_rear.jpg|321 rear view
321_front.jpg|321 front view
File:Tek 321 round.jpg|321 with round bezel
321_right_case.jpg|321 right case
Image:321_FET:JPG|Latest 321A´s frontend.
321_left_internal.jpg|321 left internal
321_right_internal.jpg|321 right internal
321_rear.jpg|321 rear view
Tek 321 round.jpg|321 with round bezel
321A_FET.JPG|Latest 321A's frontend
Tek 321a trace.jpg|321A trace
Tek 321a trace2.jpg|321A trace
321SN1557.jpg|321 with no model number on panel
Tek 321a bottom.jpg|321A bottom view
</gallery>
</gallery>
[[Category:Portable scopes]]
[[Category:300 series scopes]]
[[Category:Manual needed]]
[[Category:Specifications needed]]

Revision as of 06:33, 5 June 2019

Manuals – Specifications – Links – Pictures

The Tektronix 321 is a very compact single-trace, single-timebase portable oscilloscope that is almost completely solid state. It was introduced on April 8th, 1960.

The 321 includes several germanium bipolar transistors, which are a known reliability problem.

The 321A was introduced in 1964. The 321 and 321A have slightly different circuits. Early instances of the 321 (sn pre-720) use a 5718 peanut tube as the front-end cathode follower.

Later 321 and 321A use a 7586 Nuvistor for that role. Latest 321A (SN6000 up) use a FET 151-1011-01. In several circuits, the 321 uses OC170 transistors where the 321A uses 2N2207 transistors.

Key Specifications

Bandwidth 5 MHz (321) / 6 MHz (321A)
Rise time 70 ns (321) / 64 ns (321A)
Sweep 0.5 μs/Div to 0.5 s/Div, 1—2—5, ×5 magnifier (i.e. to 50 ns/Div)
Deflection 10 mV/Div to 20 V/Div
Input impedance 1 MΩ // 35 pF
Calibrator 0.5 Vp-p, about 2 kHz
CRT T3210 or T3211-31 or 154-433, P31 phosphor, 10 × 6 Div. @ 6.25 mm (0.25"), 4 kV acceleration
AC Power 90—136 V or 180—272 V, 20 W
DC Power 11.5—35 V, 8.5 W min., 24.5 W max., 700 mA current typ.
Battery Ten size "D" NiCd cells, runtime 5 h (4 Ah cells), 3 h (2.5 Ah cells), charge time 16 h
Dimensions 21.67 cm × 14.6 cm × 40 cm (8.5" × 5.75" × 16")
Weight unknown, about 5 kg
Features
  • Ext Trig / X input (supports X-Y displays)
  • External blanking input (Z modulation)
  • Built-in battery

External Power Connector

Douglas W Jones wrote:

I've got a Tektronix 321 scope (serial number 001917) that I need to run from an external DC supply. The problem is, I have only the line cord, and not the DC cord. The power input plugs on the scope are obviously custom, long predating the standard IEC plug everyone uses today.

So I improvised. The pin spacing for the 3-pin DC input plug is very close to the spacing of Molex 6, 9 and 12-pin plugs, and the pin diameter is not too much larger than Molex uses. So, I picked up a 6-pin Molex housing and 3 female molex pins, and then cut the housing down to 4 pins (using my pocket knife).

I used an old IEC cord for the DC input wires, with the plugs cut off both ends. I attached the wires on one end to the molex pins and pushed them into the housing, then jammed to housing down onto the Tektronix connector (this flared the female Molex pins to fit the Tektronix pins. The other end of the DC power cord got banana plugs to fit the output posts of my DC power supply.

The net result works fine, plugs and unplugs nicely, and unlike other power supply solutions I've seen, involves no changes to the scope.

Added note: My bench supply has an analog Ammeter on it. The starting surge of the 321 is about 1.5 amps, perhaps 2, tapering down to 0.7 amps in under a second. It seems to draw a steady 0.7A regardless of what you're doing with it. The current drain doesn't change when you vary the supply from 12 to 18V — this is because the 321 uses a linear regulator.

Links

Pictures