7CT1N

Template:Plugin Sidebar 2 The Tektronix 7CT1N is a curve tracer plug-in for 7000-series scopes. 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 x1000 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 (x 1 mode) 10 nA/Div to 20 μA/Div, 1-2-5 steps (x 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/Div to 1 V/Div in 1-2-5 sequence, 1 kΩ current limit
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

Common Problems

C30 and C32 (100 μF, 25 V) have a tendency to leak or short, causing associated resistors R30 and R32 (240 Ω, .25W, 5%) to overheat and fail.

A good preventive maintenance procedure would be to replace these two capacitors with modern equivalents. Three 7CT1N units purchased online had this fault, and replacement of the capacitors and resistors restored proper operation.

Prices

Year	Price	2015 value
1971	$400	$2,320
1980	$1,000	$2,870
1990	$2,100	$3,790

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