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The Tektronix 321 is a very compact single-trace, single-timebase portable oscilloscope that is almost completely solid state. | {{Oscilloscope Sidebar | ||
|manufacturer=Tektronix | |||
|series=300-series scopes | |||
|model=321 | |||
|summary=Portable single channel scope | |||
|image=Tek 321 trace.jpg|321 front view | |||
|caption=Tek 321 front | |||
|introduced=1960 | |||
|discontinued=1972 | |||
|designers=Oz Svehaug;Oliver Dalton;Hiro Moriyasu | |||
|manuals= | |||
* [[Media:070-196.pdf|Tektronix 321 Manual 070-196]] | |||
* [[Media:070-0425-01.pdf|Tektronix 321A Manual 070-0425-01]] S/N 100-5999 (OCR) | |||
* [[Media:Tek 321 irb.pdf|Tektronix 321 Instrument Reference Book]] (OCR) | |||
* [[Media:Tek 321a mod 128A.pdf|Tektronix 321A Mod 128A]] | |||
* [[Media:070-0891-00.pdf|Tektronix 321A SN 6000 up]] (OCR) | |||
* [[Media:321 announce.pdf|Tektronix 321 Announcement]] | |||
* [[Media:070-425.pdf|Tektronix 321A Manual]] (OCR) | |||
* [[Media:tek_321_fcp.pdf|Tektronix 321 factory calibration procedure]] (bad-OCR) | |||
* [[Media:Tek 321a fcp june 1968.pdf]] | |||
* [[Media:Tek 321 mod 797A.pdf]] | |||
* [[Media:Tek 321 mod 799F.pdf]] | |||
* [[Media:Tek 321 single sweep lockout early schematics.pdf]] | |||
* [[Media:Early tek 321 schematics.pdf]] | |||
}} | |||
The '''Tektronix 321''' is a very compact single-trace, single-timebase portable oscilloscope that is almost completely solid state. | |||
Design work took place in 1959 and it was [[introduced in 1960|introduced on April 8th, 1960]]. | |||
It was designed by [[Oz Svehaug]], [[Oliver Dalton]], and [[Hiro Moriyasu]]. | |||
* | 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. | |||
==Power Supply== | |||
The 321 uses a DC-DC converter to generate the DC voltages needed for the scope. | |||
Prior to serial number 720, 321s used the [[120-153]] transformer along with a separate high voltage power supply with its own transformer | |||
the +3350 V CRT anode voltage. | |||
Starting at serial number 720, all DC voltages (including the CRT anode voltage, via a voltage multiplier) are generated by a single power supply | |||
based on the [[120-210]] transformer. | |||
{{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. | |||
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> | |||
tek-321-front.jpg | 321 rectangular front | |||
tek-321-round-front.jpg | 321 round front | |||
tek-321-round-vs-rect.jpg | 321 round vs. rectangular models | |||
321_pair.JPG | 321 and 321A | |||
321_front.jpg|321 front view | |||
321_right_case.jpg|321 right case | |||
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> | |||
{{Parts|321}} | |||
{{Parts|321A}} | |||
[[Category:Portable scopes]] | |||
[[Category:300 series scopes]] |