The Tektronix 7A14 is a 120 MHz current probe amplifier vertical plug-in for 7000 series, intended to be used with passive current probes such as the P6021 and P6022.

Tektronix 7A14
120 MHz current probe amplifier
Tektronix 7A14

Compatible with 7000-series scopes

Produced from 1969 to 1975

Manuals
(All manuals in PDF format unless noted otherwise)

The P6019 and P6020 also work but with reduced bandwidth flatness, and the P6019 needs a 131-0750-00 adapter (s.b.)

The 7A14 is one of the original plug-in modules introduced at the start of the 7000 series in 1969.

Key Specifications

Deflection 1 mA/Div to 1 A/Div in 1–2–5 sequence
Bandwidth P6021: 25 Hz – 50 MHz (55 MHz in 79xx)
P6022: 250 Hz – 105 MHz (120 MHz in 79xx, 80 MHz in 76xx)
Features Bandwidth limiting switch (20 MHz), polarity switch

Operation

In the 7A14, the ring around the input BNC connector that is used to identify ×10/×100 probes on voltage probes serves the purpose of detecting the difference between the P6021 and P6022 probes, and switching in appropriate gain and frequency compensation. The P6021 shorts this ring to ground, directly switching three relays connected to −15 V internally. When connecting a P6019 probe, the ring must also be grounded but the probe connector does not have the matching pin. The 131-0750-00 adapter solves this problem.

The front panel gain and low frequency compensation screwdriver adjustments do not differentiate between the P6021 or P6022 probes, i.e. swapping probes requires re-adjustment. Note that the low frequency compensation adjustment has a large impact on waveform accuracy and requires careful adjustment to a certain slope when using a 1 kHz calibrator signal as discussed in the manual.

Links

Documents Referencing 7A14

Document Class Title Authors Year Links
Tekscope 1969 V1 N5 Oct 1969.pdf Article Introducing the New Generation 1969
Tekscope 1969 V1 N6 Dec 1969.pdf Article A New Logic for Oscilloscope Displays 1969

Internals

The 7A14 uses twelve Tek-made miniature relays that can be a service issue.

The amplifier is an 8-stage discrete differential design. The plug-in contains no integrated circuits.

Prices

Year 1969 1974
Catalog price $575 $700
In 2023 Dollars $4,800 $4,400

Pictures

Measurement examples

Current through a 50 Ω resistor measured with P6021 (top trace) compared to the voltage across the resistor (bottom trace). Measured with 7854 and 7A26 illustrating the low frequency limitation of the different probe termination methods. In the 10 mA/mV setting of the termination box the gain of the scope's vertical amplifier is insufficient to scale the current trace to the same nominal size as the voltage trace.
The signal shown is a squarewave from a PG501 @ 4 Vp-p into 50 Ω = 80 mAp-p.

5 kHz Squarewave

500 Hz Squarewave

50 Hz Squarewave

Components

Some Parts Used in the 7A14

Part Part Number(s) Class Description Used in
148-0034-00 148-0034-00 Discrete component miniature DPDT relay 7A11 7A13 7A14 7B70 7B71 7503 7904 7904A
148-0035-00 148-0035-00 Discrete component miniature SPDT relay 7A13 7A14 7B70 7B71