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Tektronix Type (53)C
Dual-trace 8.5 (24) MHz amplifier
Tektronix Type C (later version)

Compatible with 500-series scopes

Produced from 1954 to 1959


Manuals – Specifications – Links – Pictures
Actually, there never was a Type C, but that name is sometimes used as shorthand for the official "Type 53C" and "Type 53/54C" nomenclatures.

The Tektronix Type 53C is a dual-trace plug-in for 500-series scopes. It was introduced along with the 531 and 535 mainframes in 1954. It is very possibly the first dual-trace scope or plugin ever.


In the 53x scopes (Tek never documented its performance in the 540's), its bandwidth is 8.5 MHz, and like most letter-series plug-ins, its maximum vertical sensitivity is 50 mV/div. Unlike the Type A and Type B, the Type C had the ability to invert the signal before display.

Type 53C was replaced by Type 53/54C in 1956 when the 541 and 545 were introduced. The Type 53/54C's bandwidth is 24 MHz in those scopes. In 1959 it was replaced by Type CA.


At 15 tubes, the Type 53/54C and Type CA have the highest tube count of any letter-series plug-in. Each channel consists of a 6AK5 cathode-follower driving a 12AU6 differential pair which drives a 6AU6 differential pair. The two channels converge on a 12AT7 cross-coupled cathode-follower. Four more tubes, a 6AL5 and three 12AT7's, comprise a logic circuit which determines which channel drives the output at any given moment. The options are A, B, CHOPPED, and ALT.



Some Parts Used in the C

Page Class Description Used in
12AT7 Vacuum Tube (Double Triode) dual high-gain triode 180 315 360 502 502A 512 513 513D 514 514AD 514D 524D 529 RM529 544 546 547 556 3A2 1M1 A B C G H K L M K R S Z
12AU6 Vacuum Tube (Pentode) RF pentode 112 512 556 575 545 549 581 585 A B C G K H L M O R S Z
12AU7 Vacuum Tube (Double Triode) twin medium-μ triode 122 181 502 502A 512 535 545 545A 545B 547 549 555 575 581 581A 585 585A C D E Q
6AK5 Vacuum Tube (Pentode) RF pentode B C CA G K L S Z 517
6AU6 Vacuum Tube (Pentode) RF pentode 107 181 310 502 502A 512 513 529 RM529 531 531A 535 545 545A 546 547 549 555 575 581 581A 585 585A C CA Q