221

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Tektronix 221
5 MHz miniature analog scope
Tektronix 221

Produced from 1975 to 1991

Manuals
Manuals – Specifications – Links – Pictures

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)
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)

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 opamps made from discrete transistors. One drives the top deflection plate and the other drives the bottom plate.

The power supply in the 221 uses the 120-0876-00 transformer.

MOD 290A is found on a version made for IBM, which adds a Single Sweep function, and a "Property of IBM" engraving.

Pictures