7CT1N

Template:Plugin Sidebar 2 The Tektronix 7CT1N is a curve tracer plug-in for 7000-series scopes. The 5CT1N plug-in for 5000-series scopes is very similar.

It can be installed in either a vertical or a horizontal compartment, a front-panel switch must be set accordingly. A pull-out cable with a plastic BNC plug connects to the input of a module installed in the corresponding plugin for the other axis, with a fixed 100 mV/Div scaling compatible with time base X inputs.

Internally, a variable-amplitude 55 Hz triangle-wave source supplies a transformer to step up the drive voltage and decouple it from ground (Emitter terminal). A step source supplies base current or gate voltage to the DUT.

The amplifier for the current axis can be switched into a ÷1000 mode to detect leakage currents (of typical 1970s semiconductors, anyway).

Key Specifications

DUT drive voltage (C-E)	positive (NPN or N-channel) or negative (PNP or P-channel) half-waves 7.5 V, 0.5 V/Div, 240 mA peak 30 V, 2 V/Div, 60 mA peak 75 V, 5 V/Div, 24 mA peak 300 V, 20 V/Div, 6 mA peak HV warning light on for > 50 V peak power 500 mW
DUT current display	10 μA/Div to 20 mA/Div, 1−2−5 steps (×1 mode) 10 nA/Div to 20 μA/Div, 1−2−5 steps (÷1000 mode)
Base/Gate drive	0 to at least 10 steps dual polarity variable offset, at least +/− 5 steps current mode: 1 μA/Step to 1 mA/Step in 1−2−5 sequence voltage mode: 1 mV/Step to 1 V/Step in 1−2−5 sequence (via 1 kΩ current limiting resistor)
DUT connection	Three 4 mm jacks / binding posts
DUT adapters	013-0072-00 Axial diodes 013-0069-00 Devices with long leads 013-0070-01 Transistors in TO-3 or TO-66 cases 013-0074-00 Transistors with stud leads 013-0110-00 Diodes with stud leads 013-0112-00 Transistors in TO-36 cases 013-0128-00 Transistors in TO-5 or TO-18

Links

• Tekscope Vol. 4 No. 6, Nov 1972
• Tek 7CT1N @ amplifier.cd
• Tek 7CT1N @ barrytech.com
• A homebrew test adapter
• Dennis Tillman: An Inexpensive Vacuum Tube Curve Tracer Adapter for All Tektronix Semiconductor Curve Tracers

Common Problems

C30 and C32 (100 μF, 25 V) are under-rated and therefore have a tendency to leak or short, causing associated resistors R30 and R32 (240 Ω, 0.25 W, 5%) to overheat and fail. C30 and C32 should be replaced with modern equivalents rated above 35 V.

Prices

Year	Price	2019 value
1971	$400	$2,510
1980	$1,000	$3,080
1990	$2,100	$4,080

Pictures

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  7CT1N front

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  7CT1N left side

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  7CT1N right side

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  7CT1N tracing a BC337 NPN Si transistor

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  10 mA tunnel diode. 7A13 is set to 10 mV/div for ×10 horizontal expansion.