7A29

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Tektronix 7A29
1 GHz amplifier
7A29 front view (sans options)

Compatible with 7000-series scopes

Produced from 1978 to 1991

Manuals


Manuals – Specifications – Links – Pictures

The Tektronix 7A29 is a 1 GHz single-channel vertical plug-in for 7000-series scopes. It is primarily intended for the 7103 and 7104. Like with the 7A19, a variable signal delay was available as an option. The 7A29 was designed by John Addis.

There is also a 7A29P, which has digitally programmable gain, intended for the 7000 series digitizers and the 7854 only.

The 7F10 uses the 7A29's amplifier board after the optical/electrical converter.

Specifications

Bandwidth 1 GHz (in 7104)
Input impedance 50±1 Ω, VSWR <1.2:1 from DC to 1 GHz (10 mV/Div: 1.4:1, Opt.4: 1.5:1)
Max. input max. 10 VRMS or 1 Ws pulses not exceeding 50 V; max. 100 V additional DC component in AC mode
Deflection 10 mV/div to 1 V/div, 1-2-5, ±2%; variable 2.5:1
Channels Single channel
Recommended probes P6056 (×10), P6057 (×100)
Options Option 4: variable delay (1 ns)

Internals

The 7A29 employs a number of Tek-made custom Hypcon-packaged hybrids, the 155-0180-00 fast input protection, 155-0181-00 input amplifier and 155-0175-00 trigger amplifier (2 ×). It also uses the 155-0076-00 input protection IC initially developed for the 485.

It uses a "feed-beside" scheme implemented with standard low-frequency operational amplifiers to compensate for low-frequency anomalies in the frequency response that are attributed to transistor heating.

The input connector is a special Tek-made part that is exactly 50 Ω. Typical BNC connectors are around 52 Ω.

The 7A29 does not use the ±50 V supplies provided by the mainframe.

Although the 7A29 has a VARIABLE gain control, this control has the undesirable side-effect of also affecting bandwidth. See bandwidth versus VARIABLE gain plot below.

Repair issues

The input attenuator connected to the Volts/Div switch is very delicate. Three plastic levers actuate the ×2, ×10, and ×5 attenuator switches. Small metal rollers are clipped into the plastic levers and ride on cams. The plastic clips did not age well and have become very brittle. Combined with lack of lubrication on the metal rollers this often leads to broken plastic clips and missing rollers. Do not operate a stiff Volts/Div switch and lubricate rollers before use!

Links

Pictures

Internal

Schematics

Measurements

Custom ICs used in the 7A29

Page Class Manufacturer Model Part nos Description Designers Used in
155-0076-00 Monolithic integrated circuit Tektronix M94 155-0076-00 input protection and probe logic John Addis Wink Gross 485 7A29 7A29P 11A52 11A71 11A72 SCD1000
155-0175-00 Monolithic integrated circuit Tektronix H476 155-0175-00 broadband amplifier John Addis Wink Gross Carl Battjes 7904A 7912HB 7934 7104 R7103 7A29 7A29P 7F10 067-0587-02 067-0587-10 11A71 SCD1000 EG&G N-AM-173A
155-0180-00 Hybrid integrated circuit Tektronix H489 155-0180-00 fast input protection John Addis Wink Gross 7A29 7A29P 7F10 11A71
155-0181-00 Hybrid integrated circuit Tektronix H500 155-0181-00 input amplifier John Addis Wink Gross 7A29 7A29P 7F10 11A71