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7A13: Difference between revisions
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Vintage dave (talk | contribs) (Replace 070-1948-00 supplement with better. Two scans, courtesy Hakan Hintze aka Zenith5106) |
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* [[Media:7A13 B250000-up Manual Change.pdf|Supplement for 070-1948-00: errata plus LD121A mod]] | * [[Media:7A13 B250000-up Manual Change.pdf|Supplement for 070-1948-00: errata plus LD121A mod]] | ||
* [[Media:7A13 B200000-up Manual Change.pdf|Another Supplement for 070-1948-00]] | * [[Media:7A13 B200000-up Manual Change.pdf|Another Supplement for 070-1948-00]] | ||
* [[Media:TB-9-6625-2132-35.pdf|TB 9-6625-2132-35 Calibration Procedure for AM-6881/U (7A13) and AM-6786/U (7A22)]] | * [[Media:TB-9-6625-2132-35.pdf|TB 9-6625-2132-35 Calibration Procedure for AM-6881/U (7A13) and AM-6786/U (7A22)]] | ||
}} | }} | ||
The '''Tektronix 7A13''' is a "differential comparator" vertical plug-in for [[7000-series scopes]], i.e. a fast differential amplifier with adjustable DC offset. | The '''Tektronix 7A13''' is a "differential comparator" vertical plug-in for [[7000-series scopes]], i.e. a fast differential amplifier with adjustable DC offset. | ||
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which is implemented through small light bulbs above the dial with plastic light guides to make the decimal point appear between the digits. | which is implemented through small light bulbs above the dial with plastic light guides to make the decimal point appear between the digits. | ||
In contrast to the [[back-lit switches]], the decimal point lamps are supplied from logic +5 V | In contrast to the [[back-lit switches]], the decimal point lamps are supplied from logic +5 V | ||
so they work | so they also work in mainframes without switch light supplies, e.g. the 76x3s. | ||
In the newer version, the zener-derived reference voltage is always positive. | In the newer version, the zener-derived reference voltage is always positive. | ||
A 10-turn pot for coarse selection combines with a single-turn pot for fine control. | A 10-turn pot for coarse selection combines with a single-turn pot for fine control. | ||
The resultant voltage is displayed on a 4-digit simplified DVM built around a [[Fairchild 3814]] 4½ digit DVM controller. | The resultant voltage is displayed on a 4-digit simplified DVM built around a [[Fairchild 3814]] 4½ digit DVM controller. | ||
(S/N B250000 switched to a [[Siliconix LD121A]].) | (S/N B250000+ switched to a [[Siliconix LD122]]/[[Siliconix LD121A|LD121A]] chipset.) | ||
For negative values of V<sub>C</sub>, an opamp polarity inverter circuit is switched in. | For negative values of V<sub>C</sub>, an opamp polarity inverter circuit is switched in. | ||
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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 7A13 uses twelve [[miniature relays]] similar to those used in the [[7A11]]. These are very rare. | ||
The [ | The [https://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. | describes a possible replacement with a modern component. See also the IK1ZYW link below. | ||
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* [[Media:Tekscope 1970 V2 N5 Oct 1970.pdf|Amplitude measurements to better than 1%. Tekscope Vol. 2 No. 5, October 1970]] | * [[Media:Tekscope 1970 V2 N5 Oct 1970.pdf|Amplitude measurements to better than 1%. Tekscope Vol. 2 No. 5, October 1970]] | ||
* [ | * [https://www.amplifier.cd/Test_Equipment/Tektronix/Tektronix_7000_series_amplifier/amplifier_7A13.htm Tek 7A13 @ amplifier.cd] | ||
* [ | * [https://www.radiomuseum.org/r/tektronix_differential_comparator_unit_7a13.html Tek 7A13 @ radiomuseum.org] | ||
* [https://ik1zyw.blogspot.com/2007/09/tektronix-7a13-broken-relays.html Tek 7A13 broken relays @ IK1ZYW Labs] | |||
* [ | * [https://www.pa4tim.nl/?p=5755 Repairing 7A13 relays @ PA4TIM] (how to take relays apart, inside photos) | ||
* [ | |||
* [https://www.youtube.com/watch?v=IqE_LNXnPyo Tektronix 7A13 Repair and Alignment] by Zenwizard Studios @ YouTube | * [https://www.youtube.com/watch?v=IqE_LNXnPyo Tektronix 7A13 Repair and Alignment] by Zenwizard Studios @ YouTube | ||