221
The Tektronix Type 221 is a miniature 5 MHz analog scope introduced in 1973.
Key Specifications
| Bandwidth | DC to 5 MHz |
|---|---|
| Input Impedance | 1 MΩ // 29 pF |
| Input Voltage | max. 600 V DC + Peak AC, or 600 Vp-p AC |
| Sweep Range | 200 ms to 1 μs, 17 steps |
| CRT | 154-0705-00, 6 div (V) × 10 div (H), 1 kV acceleration |
| Internal Battery | 10 rechargeable NiCd cells; runtime 2-3 hours |
| Power | 90-250 VAC @ 48−62 Hz, or 80-250 VDC; ≤ 5 W |
| Dimensions | (H/W/D) 3" × 5.25" × 9" (7.6 cm × 13.2 cm × 22.8 cm) |
| Weight | 3.5 lb (1.5 kg) |
Links
Documents referencing 221
| Document | Class | Title | Authors | Year | Links |
|---|---|---|---|---|---|
| 60AX-4741.pdf | Application Note | Floating Oscilloscope Measurements ... And Operator Protection | 1981 | A6901 • A6902 • 221 | |
| 061-4124-02.pdf | Article | Handheld and benchtop instruments service manuals | 2002 | PS280 • PS281 • PS2520 • PS2520G • PS2521 • PS2521G • TAS210 • TAS220 • TMM420 • THM500 • 212 • 214 • 221 • 222 • 224 • 305 • 314 • 335 • 336 • 2201 • 2205 |
Patents that may apply to 221
| Page | Title | Inventors | Filing date | Grant date | Links |
|---|---|---|---|---|---|
| Patent US 4166200A | Compact rotary switch construction | John E. Reichen • Scott B. Long | 1978-08-07 | 1979-08-28 | 211 • 212 • 221 |
Prices
| Year | Catalog price | In 2026 dollars |
|---|---|---|
| 1976 | $825 | ~$4,900 |
| 1977 | $975 | ~$5,400 |
| 1980 | $1,325 | ~$5,400 |
| 1982 | $1,600 | ~$5,600 |
| 1986 | $2,260 | ~$6,900 |
| 1990 | $2,950 | ~$7,600 |
Internals
The 221 has a switching power supply and built-in rechargeable batteries (which are a maintenance issue). The batteries are an integral part of the power supply, which, unmodified, will not perform properly without them.
The power supply in the 221 uses three transformers: 120-0877-00/120-0946-00 (T623) in the base drive for the line inverter, 120-0876-00 (T633) steps down and rectifies the line inverter, and 120-0875-00 (T701) in HV inverter.
The vertical output amplifier that drives the CRT plates is two op-amps made from discrete transistors. One drives the top deflection plate, the other the bottom plate.
The trigger circuit uses a 1N3713 1 mA tunnel diode.
The 221 contains one integrated circuit, a 741 op-amp that creates a virtual ground, otherwise only discrete (including dual) transistors.
MOD 290A is a version of the 221 made for IBM which adds a Single Sweep function and a "Property of IBM" engraving.
Pictures
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Side
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Front
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Front
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Panel of 221
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Panel of 221
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Probe of 221
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221 with orginal bag
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221 on top of 565
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MOD 290A variant for IBM
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MOD 290A variant for IBM
Internals
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Tek 221 - Internals, rear
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Tek 221 - Internals, LHS
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Tek 221 - Internals, top
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Tek 221 - Front Panel A1/A2 board
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Tek 221 - CRT & power supply board
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Tek 221 - Power supply board
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Tek 221 - Power supply board
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Tek 221 - Amplifier board
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Battery pack (fused)
