The 6AL5/12AL5  (European: EAA91/EB91/HAA91) (P/N 154-016,154-0016-00,154-0038-00) is a high-perveance dual diode vacuum tube with a 6.3 V, 0.3 A heater.
The 12AL5 (European type HAA91) is the same but has a 12.6 V, 0.15 A heater. Both have a B9A (Noval) miniature 9-pin base.

6AL5 Vacuum Tube

The 6AL5/12AL5 serves as the "disconnect diode" in the timebase circuit of many tube-era Tektronix scopes starting with the 511 in the 1940s and continuing through the 1960s in sweep plug-ins such as the 3B2 and other plug-ins such as Type C / Type CA.

Tektronix part number: 154-0016-00 (6AL5), 154-0038-00 (12AL5/HAA91)

Aged/Checked/Matched Pair Details
Used in Tek Part# S/N Range
535A, 545A, 585A 157-0075-00 (12AL5) All
316, 317, 502A, 516 157-0104-00 (6AL5) All
53X, 54X series, 551, 580 157-0104-02 (6AL5) All

Reference:

Tube aging procedure / Selection and checking procedure

Data and Links

Some instruments using part 6AL5

Instrument Manufacturer Class Model Description Introduced
163 Tektronix Plug-in 163 Pulse Generator Module 1952
181 Tektronix Pulse generator 181 Time-mark generator 1955
190 Tektronix Signal generator 190 Constant-Amplitude Signal Generator 1954
1M1 Tektronix Plug-in 1M1 Calibration plug-in 1964
310 Tektronix Oscilloscope 310A 4 MHz oscilloscope 1955
310A Tektronix Oscilloscope 310A 4 MHz oscilloscope 1959
315 Tektronix Oscilloscope 315 "Portable" tube scope 1952
316 Tektronix Oscilloscope 316 10 MHz 3" tube scope 1959
317 Tektronix Oscilloscope 317 10 MHz 3" tube scope 1959
3B1 Tektronix Plug-in 3B1 10 MHz time base plug-in 1962
3B1S Tektronix Plug-in 3B1S Sampling time base plug-in 1961
3B2 Tektronix Plug-in 3B2 Delaying timebase plug-in 1963
3B3 Tektronix Plug-in 3B3 Time Base plug-in 1962
3B5 Tektronix Plug-in 3B5 Automatic time base plug-in 1966
502 Tektronix Oscilloscope 502 1 MHz dual beam differential scope 1958
502A Tektronix Oscilloscope 502A 1 MHz dual beam differential scope 1963
503 Tektronix Oscilloscope 503 450 kHz differential-input scope 1960
511 Tektronix Oscilloscope 511 10 MHz Tube scope
First Tektronix oscilloscope
1947
511A Tektronix Oscilloscope 511A 10 MHz Tube scope 1948
512 Tektronix Oscilloscope 512 Early 2 MHz scope 1948
516 Tektronix Oscilloscope 516 15 MHz dual-trace scope 1960
517 Tektronix Oscilloscope 517 50 MHz scope 1951
524 Tektronix Oscilloscope 524AD TV waveform monitoring scope 1953
526 Tektronix Audio/Video 526 NTSC Vectorscope 1959
535 Tektronix Oscilloscope 535 10 (15) MHz dual-timebase scope 1954
545 Tektronix Oscilloscope 545 30 (33) MHz oscilloscope 1955
545A Tektronix Oscilloscope 545A 30 (33) MHz oscilloscope 1959
549 Tektronix Oscilloscope 549 30 MHz storage oscilloscope 1965
551 Tektronix Oscilloscope 551 27 MHz scope 1958
565 Tektronix Oscilloscope 565 10 MHz dual-beam scope 1962
570 Tektronix Curve Tracer 570 Curve tracer for tubes 1955
581 Tektronix Oscilloscope 581 100 (95) MHz oscilloscope 1959
581A Tektronix Oscilloscope 581A 85 MHz oscilloscope 1963
585 Tektronix Oscilloscope 585 100 (95) MHz oscilloscope 1959
585A Tektronix Oscilloscope 585 85 MHz oscilloscope 1963
C Tektronix Plug-in Type (53)C Dual-trace 8.5 (24) MHz amplifier 1954
T Tektronix Plug-in Type T Timebase plugin 1957
Telequipment D52 Telequipment Oscilloscope D52 6 MHz dual-beam scope 1968
Telequipment D56 Telequipment Oscilloscope D56 15 MHz 2-ch scope (?)
Telequipment S52 Telequipment Oscilloscope S52 3 MHz dual-channel scope 1968