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Tektronix 7403N
65 MHz non-storage mainframe
Tektronix 7403, front view

Produced from 1970 to 1975

(All manuals in PDF format unless noted otherwise)
Manuals – Specifications – Links – Pictures

The Tektronix 7403N is a 65 MHz oscilloscope mainframe that takes two 7000-series vertical plug-ins and one 7000-series horizontal plug-in. It has a large CRT (8 × 10 divisions @ 1.22 cm each, 154-0640-xx or 154-0672-xx tubes). There is no readout system.

There are two versions, the benchtop 7403N with the CRT above the plug-ins, and a rackmount version, the R7403N, with the CRT to the left of the plug-ins.

The 7403 was designed from the ground up. The design team, led by Phil Crosby, decided to use a discrete transistor vertical output amplifier rather than a hybrid on beryllium oxide. The output stage approximated a 3 pole MFED response with an additional real pole closer to the origin. Since the DC requirement was 3 screen diameters, the gain at the –3 dB point could be substantially less, meaning that the load resistor (and output stage dissipation) could be reduced, allowing the design to meet scan bandwidth and corner shift criteria with substantially reduced power dissipation.

The 7403N was discontinued around 1975, having been superseded largely by the popular 7603 introduced in 1973. In 1974, the 7403N had a list price (without plug-ins) of $950. In the same year, the 7603 was $1600.

Key Specifications

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The 7403N consumes a maximum of 130 watts and uses convection cooling, no fan. It weighs 30 pounds.


The power supply is a linear design, similar to that of the 7313. The vertical and horizontal amplifiers are made of discrete bipolar transistors. The only integrated circuit in the vertical signal path is U214, the vertical channel switch, a 155-0022-00.

The 7403N uses a CRT anode voltage of 12 kV, produced by a solid state voltage multiplier.


CRTs used in the 7403N

Page Part nos Description Designers Used in
T7400 154-0640-00 154-0640-05 154-0640-31 154-0640-10 154-0672-00 154-0673-00 large-screen CRT (8 × 10 divisions of 1.22 cm) 7403N 7603 Telequipment D83

Custom ICs used in the 7403N

Page Class Manufacturer Model Part nos Description Designers Used in
155-0011-00 Monolithic integrated circuit Tektronix M012 155-0011-00 clock and chop blanking Les Larson 485 7313 7403N R7403N 7503 7504 7514 7603 AN/USM-281C 7613 7623 7623A 7633 7704 R7704 7704A 7834 7844 7854 7904 7904A R7903 R7912 7912AD 7912HB 7934 7104 R7103 AN/USM-281C
155-0022-00 Monolithic integrated circuit Tektronix M036 155-0022-00 155-0022-01 analog multiplexer Gene Andrews 147 148 149 335 468 1430 1441 1461 1900 1910 2220 2221 2230 5223 5403 5440 5441 5443 5444 5A38 7313 7403N 7503 7504 7514 7603 AN/USM-281C 7613 7623 7623A 7633 7704 R7704 7704A 7834 7844 7854 R7912 7912AD 7912HB 7904 R7903 7904A 7934 7A12 7A18 7A18A 7B52 7B53N 7D10 7D11 7D12 NT-7000 P7001