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7A13: Difference between revisions
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The '''Tektronix 7A13''' is a "differential comparator" vertical plug-in for [[7000-series scopes]], i.e. a fast differential amplifier with adjustable DC offset. It is one of the first 7000 series plugins | The '''Tektronix 7A13''' is a "differential comparator" vertical plug-in for [[7000-series scopes]], | ||
i.e. a fast differential amplifier with adjustable DC offset. | |||
It is one of the first 7000 series plugins. | |||
It was designed by Bill DeVey and released along with the first 7000-series scopes in 1969/1970, | |||
and was made until the 7000 series was retired in 1992. | |||
==Operation== | ==Operation== | ||
Older versions display the comparison (offset) voltage through a mechanical dial, newer versions (from 1976 on) through an LED panel meter. In addition, this voltage is brought out through a front panel connector so it can be measured externally. | Older versions display the comparison (offset) voltage through a mechanical dial, | ||
newer versions (from 1976 on) through an LED panel meter. | |||
In addition, this voltage is brought out through a front panel connector so it can be measured externally. | |||
In differential mode, a +/-10 V common mode signal can be present at the inputs without attenuation. Either input can be switched to the comparison voltage, which is settable to four digits by a 10-step switch and a 10-turn potentiometer. In this comparator mode, the offset range is effectively 10,000 divisions. | In differential mode, a +/-10 V common mode signal can be present at the inputs without attenuation. | ||
Either input can be switched to the comparison voltage, | |||
which is settable to four digits by a 10-step switch and a 10-turn potentiometer. | |||
In this comparator mode, the offset range is effectively 10,000 divisions. | |||
On the 1 mV/Div to 50 mV/Div ranges, the gate resistors can be disabled by an internal switch, raising DC input impedance to "approximately infinite" (as indicated by a front panel lamp). | On the 1 mV/Div to 50 mV/Div ranges, the gate resistors can be disabled by an internal switch, | ||
raising DC input impedance to "approximately infinite" (as indicated by a front panel lamp). | |||
{{BeginSpecs}} | {{BeginSpecs}} | ||
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===Repair issues=== | ===Repair issues=== | ||
The 7A13 uses twelve miniature relays similar to those used in the [[7A11]]. These are very rare. The [http://www.amplifier.cd/Test_Equipment/Tektronix/Tektronix_7000_series_amplifier/amplifier_7A11.htm 7A11 repair report at amplifier.cd] describes a possible replacement with a modern component. See also the IK1ZYW link below. | The 7A13 uses twelve miniature relays similar to those used in the [[7A11]]. These are very rare. The [http://www.amplifier.cd/Test_Equipment/Tektronix/Tektronix_7000_series_amplifier/amplifier_7A11.htm 7A11 repair report at amplifier.cd] describes a possible replacement with a modern component. See also the IK1ZYW link below. | ||
Early 7A13 plug-ins were made with a mechanical counter for reading out the comparison voltage. | |||
The plastic gears in this counter don't age well. | |||
The plug-in can still be used when the counter fails, by using an | |||
external voltmeter to monitor the comparison voltage, Vc. | |||
Later 7A13 plug-ins use an LED readout instead of the mechanical counter. | |||
The LED readout is much less problematic. | |||
==Links== | ==Links== | ||