221

The Tektronix Type 221 is a miniature 5 MHz analog scope introduced in 1973.

Tektronix 221
5 MHz miniature analog scope Tektronix 221 Produced from 1975 to 1991 Manuals Tektronix 221 Manual (unlocked) Tektronix 221 Manual (bad-OCR) Mod 290A Single Sweep Modification Insert (All manuals in PDF format unless noted otherwise)

Manuals – Specifications – Links – Pictures

Key Specifications

Bandwidth	DC to 5 MHz
Input Impedance	1 MΩ // 29 pF
Input Voltage	max. 600 V DC + Peak AC, or 600 V_p-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 V_AC @ 48−62 Hz, or 80-250 V_DC
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, 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 opamp 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

Side
Front
Front
Panel of 221
Panel of 221
Probe of 221
221 with orginal bag
221 on top of 565
MOD 290A variant for IBM
MOD 290A variant for IBM

Internals

Tek 221 - Internals, rear
Tek 221 - Internals, LHS
Tek 221 - Internals, top
Tek 221 - Front Panel A1/A2 board
Tek 221 - CRT & power supply board
Tek 221 - Power supply board
Tek 221 - Power supply board
Tek 221 - Amplifier board
Battery pack (fused)

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