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 |
| Operating Time on Battery | 2-3 hours |
| Internal Battery | 10 rechargeable NiCd cells |
| Line Voltage | 90-250 VAC @ 48−62 Hz, or 80-250 VDC |
| Power Consumption | 5 W @ 250 V |
| 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 |
Prices
| Year | 1976 | 1977 | 1980 | 1982 | 1986 |
|---|---|---|---|---|---|
| Catalog Price | $825 | $975 | $1,325 | $1,600 | $2,260 |
| In 2023 Dollars | $4,500 | $5,000 | $4,900 | $5,100 | $6,300 |
Internals
The 221 has a switching power supply and built-in rechargeable batteries (which are a maintenance issue). It has a transformer-coupled trigger circuit which would seem to preclude DC level-based triggering. The trigger circuit uses a 1N3713 1 mA tunnel diode. 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 power supply in the 221 uses three transformers – 120-0876-00 (T633) in the line inverter, 120-0877-00/120-0946-00 (T623) in the base drive for the line inverter and 120-0875-00 (T701) in HV inverter.
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)
Components
Some Parts Used in the 221
| Part | Part Number(s) | Class | Description | Used in |
|---|---|---|---|---|
| 120-0876-00 | 120-0876-00 | Discrete component | pot core transformer | 221 |
| 154-0705-00 | 154-0705-00 | CRT | CRT for miniature scopes | 221 |
| 2N3958 | 151-1054-00 • 151-1054-01 • 151-1054-02 | Discrete component | dual n-channel JFET | FG503 • MR501 • M3 • PG505 • SC501 • SC502 • SC503 • SG502 • 1450 • 1501 • 1502 • 1503 • 221 • 5A23N • 5CT1N • 577 • 603 • 603A • 604 • 604A • 605 • 606 • 606A • 606B • 607 • 607A • 620 • 624 • 7CT1N • 7D15 • 7D20 • 851 |
| STD933 | 152-0181-00 | Discrete component | 1 mA, 5 pF germanium tunnel diode | 1S2 • 221 • 422 |