Vacuum tubes

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Vacuum tubes aka electron tubes or (thermionic) valves were the workhorse active components in electronics up to the mid-1960s.

Tube selection

The mechanical tolerances in vacuum tube manufacturing lead to a slight variation in many tube parameters, e.g. the I/V curves, and the dynamic behavior. Further, tubes exhibit a slight change in performance in the first hours of operation.

While those variations are acceptable in many applications, Tektronix chose to age most of their used tubes to avoid the alteration of performance in the first hours of operation of new equipment, or when replacing tubes. In many applications, the same tube was further selected after aging for parameters as low grid current or matched in pairs for a particular bias condition. (In contrast to popular belief in the audiophile world, a "matched pair" of tubes is meaningless, unless the exact bias condition in operation is known and tubes are matched in that condition.)

This is the reason why there are often five or six different part numbers for the same tube, since they were differently selected.Tektronix used 157- as the part number prefix for aged/checked/matched tubes (e.g,157-0006-00 ), whereas raw tubes including CRTs were identified with 154- prefix (e.g.,154-0031-00).

Tube failure

Important failure modes of vacuum tubes include:

Loss of vacuum

aka tube "getting gassy" − can be caused by glass leak, electrode/glass interface leak, outgassing of internal tube electrodes, or broken glass.

Can often be detected by visual inspection in glass-envelope tubes, either when the envelope is visibly cracked, or if the getter (silver-colored metallic patch) has turned white or entirely disappeared.

Gassy tubes will draw more than the nominal heater power because convection transports heat away from the filament.

Slightly gassy tubes may exhibit a blue glow from inside (ionization of gas molecules by the electron beam) when operated with plate/grid supplies present.

Filament failure

broken/burned out filament (open circuit)

Loss of cathode emission

Can be measured on a tube tester or using a test jig.

Grid emission

Transport of cathode emission material to the grid can allow the grid to emit electrons when warm. This will alter the grid voltage if the grid circuit DC resistance is large. This problem is more common in certain tube types and is sometimes caused by operating the cathode/heater at higher power and higher temperature. Some Tek inputs that connect directly to vacuum tube grids also incorporate temperature sensitive circuits to null out the grid current.

Electrode damage

  • electrode damage (e.g. melting) caused by overloads − grid wires are most sensitive
  • bent electrodes or internal structures (especially noticeable in CRTs) − may be caused by excessive G force application such as dropping

Either of these can also lead to inter-electrode shorts.

Links

Tubes used in Tektronix Instruments

→ See separate page for Cathode-ray tubes (CRTs).

Page Class Model Part nos Description Used in
12A4 Vacuum Tube (Pentode) 12A4 154-0037-00 miniature 6.5 W power pentode 517 517A
12AL5 Vacuum Tube (Double Diode) 12AL5 aka HAA91 154-0038-00 high-perveance dual diode 3A2 3B2 545 545A 549 N
12AT7 Vacuum Tube (Dual Triode) 12AT7 aka ECC81 154-0039-00 dual high-gain triode 161 180 310 310A 315 316 360 502 502A 511A 512 513 513D 514 514AD 514D 516 524 529 RM529 544 546 547 556 565 570 3A2 75 3A75 1M1 A B C G H K L ML M N K R S Z
12AU6 Vacuum Tube (Pentode) 12AU6 aka HF94 154-0040-00 RF pentode 81 112 1L10 1L20 1L60 3L10 512 556 575 545 547 549 581 585 A B C G K H L ML M N O R S Z
12AU7 Vacuum Tube (Dual Triode) 12AU7 aka ECC82 154-041 154-0041-00 154-0287-00 dual medium-μ triode 104 104A 122 160 161 162 181 190 310 310A 316 317 3C66 502 502A 507 511A 512 516 517 517A 524 526 535 536 545 545A 545B 547 549 555 561 564 570 575 581 581A 585 585A C D E N Q Hickok 1825
12AW6 Vacuum Tube (Pentode) 12AW6 154-0042-00 sharp cutoff pentode 513
12AX7 Vacuum Tube (Dual Triode) 12AX7 aka ECC83 154-043 154-0043-00 dual triode 3C66 513 524 531 531A 535 536 545 545A 545B 546 547 549 555 570 581 581A 585 585A E Q Hickok 1825
12B4 Vacuum Tube (Triode) 12B4(A) 154-044 154-0044-00 power triode 126 310 310A 316 317 502 502A 524 526 541 541A 535 535A 545 545A 546 547 570 549 551 555 513 581 581A 585 585A
12BH7 Vacuum Tube (Dual Triode) 12BH7 154-0046-00 dual triode 506 517A 561A 561S 564 567
12BW4 Vacuum Tube (Dual Diode) 12BW4 dual diode
12BY7A Vacuum Tube (Pentode) 12BY7A aka EL180 154-047 154-0047-00 miniature 6.5 W power pentode 106 163 524 531 533 535 536 541 543 535 545 545A 549 555 75 3A75 3B5
12BZ7 Vacuum Tube (Dual Triode) 12BZ7 154-048 154-0048-00 dual triode 524 570
1B3GT Vacuum Tube (Diode) 1B3GT 154-091 154-0091-00 high-voltage rectifier 511A
1V2 Vacuum Tube (Diode) 1V2 154-004 154-0004-00 high-voltage rectifier 511A
1X2 Vacuum Tube (Diode) 1X2 aka DY80 154-0005-00 high-voltage rectifier 420 507 565
2X2 Vacuum Tube (Dual Rectifier) 2X2 154-0085-00 dual rectifier 511
4CX250F Vacuum Tube (Tetrode) 4CX250F (7204) 154-0300-00 beam power tetrode 519
5642 Vacuum Tube (Diode) 5642 aka DY70 154-0051-00 154-0079-00 directly-heated high-voltage rectifier 310 310A 316 317 360 453 502 502A 503 504 506 513 515 516 524 529 RM529 533 533A 535 536 543 543A 543B 545 545A 545B 547 551 555 556 560 561 561A 561S 564 567 570 575 581 581A 585 585A 647 647A
5654 Vacuum Tube (Pentode) 5654 aka E95F 154-0206-00 154-0084-00 RF pentode B L ML
5687 Vacuum Tube (Dual Triode) 5687 dual triode
5718 Vacuum Tube (Triode) 5718 aka EC71 154-0053-00 subminiature high-frequency triode 321 P500CF P170CF
5751 Vacuum Tube (Dual Triode) 5751 154-0094-00 dual triode E
5814 Vacuum Tube (Double Triode) 5814 154-0054-00 154-0316-00 twin medium-μ triode D
5842 Vacuum Tube (Triode) 5842 aka CK5842 aka 417A 154-0408-00 157-0098-00; high-gm UHF triode 2A61
5879 Vacuum Tube (Pentode) 5879 154-0055-00 sharp-cutoff pentode 112 512 D E Hickok 1825
5894 Vacuum Tube (Tetrode) 5894 aka QQE06/40 154-0130-00 dual power tetrode 536
5AR4 Vacuum Tube (Dual Rectifier) 5AR4 aka GZ34 154-0168-00 dual rectifier 502 502A 160
5R4GY Vacuum Tube (Dual Rectifier) 5R4GY 154-0007-00 dual rectifier 517 517A
5U4 Vacuum Tube (Dual Rectifier) 5U4 154-086 154-0086-00 dual rectifier 511
5V4G Vacuum Tube (Dual Rectifier) 5V4G 154-008 154-0008-00 dual rectifier 104 104A 160 511A 514
5Y3 Vacuum Tube (Diode) 5Y3 154-009 154-0009-00 rectifier 190
5Y3GT Vacuum Tube (Dual Rectifier) 5Y3GT 154-0009-00 dual rectifier
6080 Vacuum Tube (Dual Triode) 6080 aka ECC230 154-0056-00 154-0315-00 dual power triode 132 160 316 317 516 535 535A RM35A 541 541A 535 536 545 545A 545B 546 547 549 565 567 575 581 581A 585 585A
6110 Vacuum Tube (Dual Diode) 6110 154-0240-00 small-signal dual diode 190
6197 Vacuum Tube (Pentode) 6197 154-0146-00 7.5 W power pentode 516 531 533 535 535A 547 556 75 3A75
6201 Vacuum Tube (Dual Triode) 6201 aka E81CC dual high-gain triode Nelson-Ross PSA-011
6360 Vacuum Tube (Pentode) 6360 aka QQE03/12 154-0191-00 dual beam power tube 536
6688 Vacuum Tube (Pentode) 6688 aka E180F  aka 6Ж9П 154-0215-00 miniature high-slope VHF/UHF pentode P80 3T77 3T77A 4S2A 526 TR-4602
6922 Vacuum Tube (Dual Triode) 6922 aka E88CC 154-0195-00 dual triode 3S76 4S2
6939 Vacuum Tube (Dual Tetrode) 6939 aka QQE02/5, QQV02/6 dual tetrode 581 585
6AB4 Vacuum Tube (Dual Triode) 6AB4 aka EC92 154-0010-00 high-gain triode
6AC7 Vacuum Tube (Pentode) 6AC7 154-011 154-0011-00 RF pentode 511 511A
6AG5 Vacuum Tube (Pentode) 6AG5 aka EF96  aka 6Ж3П sharp-cutoff RF pentode
6AG7 Vacuum Tube (Pentode) 6AG7 154-012 154-0012-00 9 Watt power pentode 104 104A 105 112 511 511A 512 513 514 517 517A 524
6AH6 Vacuum Tube (Dual Triode) 6AH6  aka 6Ж5П 154-0013-00 RF pentode 524
6AK5 Vacuum Tube (Pentode) 6AK5 aka EF95  aka 6Ж1П 154-0014-00 154-0206-00 154-0084-00 RF pentode B C CA G K L ML S Z 517 517A 524
6AK6 Vacuum Tube (Pentode) 6AK6 154-0015-00 power pentode 315
6AL5 Vacuum Tube (Dual Diode) 6AL5/12AL5 aka EAA91/EB91/HAA91 154-016 154-0016-00 154-0038-00 high-perveance dual diode 163 181 190 1M1 310 310A 315 316 317 3B1 3B1S 3B2 3B3 3B5 502 502A 503 511 511A 512 516 517 517A 524 526 535 535A 545 545A 549 551 565 570 581 581A 585 585A C T Telequipment D56 Telequipment S52
6AN8 Vacuum Tube (Triode/Pentode) 6AN8 154-078 154-0078-00 triode-pentode combo 310 310A 316 317 360 502 502A 516 517 517A 526 565 570 575 N
6AQ5 Vacuum Tube (Pentode) 6AQ5 aka EL90 154-017 154-0017-00 beam pentode 310 310A 316 360 507 511A 512 517 517A 524 536 570 575
6AR8 Vacuum Tube (Pentode) 6AR8 154-0200-00 beam-switching tube 526
6AS5 Vacuum Tube (Pentode) 6AS5 154-0018-00 5.5 W beam pentode 517 517A 524
6AS7 Vacuum Tube (Pentode) 6AS7/6AS7G 154-020 154-0020-00 dual power triode 160 506 511A 512 513 517 517A 524 561 561A 561S 564
6AU5 Vacuum Tube (Pentode) 6AU5 154-021 154-0021-00 10 W beam power pentode 507 513 516 517 517A 531 535 541 535 545 547 581 581A 585 585A
6AU6 Vacuum Tube (Pentode) 6AU6 aka EF94  aka 6Ж4П 154-0022-00 157-0073-00 157-0059-00 154-0284-00 RF pentode 107 160 181 190 60 2A60 72 3A72 3C66 310 310A 316 317 360 502 502A 506 511 511A 512 513 516 517 517A 524 526 529 RM529 531 531A 535 536 545 545A 546 547 549 555 561 561A 561S 564 565 567 570 575 581 581A 585 585A 80 C CA Q
6AU8 Vacuum Tube (Triode/Pentode) 6AU8 154-0132-00 triode-pentode combo T
6AW8 Vacuum Tube (Triode/Pentode) 6AW8 154-0095-00 triode-pentode combo 132 160 541 535 545
6AX4 Vacuum Tube (Diode) 6AX4 154-113 154-0113-00 diode 570
6AX5 Vacuum Tube (Dual Rectifier) 6AX5(GT) 154-023 154-0023-00 rectifier 570
6BA8 Vacuum Tube (Triode/Pentode) 6BA8 154-0163-00 triode-pentode combo 59 2A61 72 3A72 3A2
6BA8A Vacuum Tube (Triode/Pentode) 6BA8A 154-0163-00 triode-pentode combo 59 3A72 526
6BC7 Vacuum Tube (Diode) 6BC7 154-0232-00 triple diode 503 504 565 67 2B67
6BE6 Vacuum Tube (Pentode) 6BE6 aka EK90 154-0025-00 heptode 130
6BH6 Vacuum Tube (Pentode) 6BH6 154-0026-00 154-0285-00 pentode 130 162 310 310A 512 517 517A 524 Nelson-Ross PSA-011
6BJ7 Vacuum Tube (Diode) 6BJ7 154-0453-00 triple diode 503 526 565
6BJ8 Vacuum Tube (Triode, Dual Diode) 6BJ8 154-0305-00 medium-μ triode + dual diode TU-4 51
6BL8 Vacuum Tube (Triode/Pentode) 6BL8 aka ECF80  aka 6Ф1П 154-0278-00 triode-pentode combo 67 2B67 3B1 3B1S 3B2 3B3 3B4 503 504 506 516 549 561 561A 561S 564 565 567 Telequipment D52 Telequipment D56 Telequipment S31 Telequipment S32 Telequipment S32A Telequipment S51 Telequipment S52
6BQ5 Vacuum Tube (Pentode) 6BQ5 aka EL84 power pentode
6BQ7 Vacuum Tube (Dual Triode) 6BQ7 dual triode 315
6BQ7A Vacuum Tube (Dual Triode) 6BQ7A aka ECC180/E180CC 154-028 154-0028-00 157-0022-00 157-0003-00 dual triode 107 163 181 310 315 316 360 524 531 532 535 536 541 545 570 T
6BW4 Vacuum Tube (Dual Diode) 6BW4 154-0119-00 dual diode 126 502 502A 524 575
6BW7 Vacuum Tube (Pentode) 6BW7 154-0028-00 pentode 130
6BY8 Vacuum Tube (Pentode) 6BY8 154-0414-00 diode-pentode 547
6C4 Vacuum Tube (Triode) 6C4 aka EC90 154-029 154-0029-00 VHF triode 190 3B2 507 511 511A 517 517A Chemtrix 205
6CA4 Vacuum Tube (Dual Rectifier) 6CA4 aka EZ81 154-0119-00 dual rectifier Telequipment S31 Telequipment S32
6CB6A Vacuum Tube (Pentode) 6CB6(A) aka EF190 154-0030-00 pentode 105 112 316 317 503 504 513 517 517A 541 535 545 63 2A63
6CD6GA Vacuum Tube (Pentode) 6CD6-GA 154-0112-00 20 W beam-power pentode 570
6CG7 Vacuum Tube (Dual Triode) 6CG7 154-0134-00 dual triode 3C66 575 Q
6CL6 Vacuum Tube (Pentode) 6CL6 154-031 154-0031-00 154-0286-00 7.5 W power pentode 132 310 310A 316 317 515 524 525 531 535 535A 545 545A 545B 549 570 581 581A 585 585A 3A74
6CW4 Vacuum Tube (Triode) 6CW4 154-0323-00 Nuvistor triode 1A7 3A8 3B2 3S76 6R1 565 S-311
6CW5 Vacuum Tube (Pentode) 6CW5 aka EL86 154-0202-00 power pentode 132 526 547 General Radio 1124 Telequipment D56
6CY5 Vacuum Tube (Tetrode) 6CY5 154-0207-00 tetrode 581 585 581A 585A
6CZ5 Vacuum Tube (Pentode) 6CZ5 154-0167-00 power pentode 317 502 506 526 555 561 561A 561S 564 565 567
6DE7 Vacuum Tube (Triode) 6DE7 154-0188-00 dual triode 526
6DJ8 Vacuum Tube (Dual Triode) 6DJ8 aka ECC88  aka 6Н23П 154-0187-00 154-0305-00 dual triode 132 161 310A 316 317 502 502A 503 504 506 515 516 519 526 529 RM529 533 535 536 543 544 545 545A 545B 546 547 549 555 556 561A 561S 564 565 567 581 581A 585 585A 661 1A4 1S1 60 2A60 63 2A63 67 2B67 3A1 3A1S 3A2 3A3 3A6 3A7 72 3A72 75 3A75 4S2 51 3B1 3B1S 3B2 3B3 3B4 3M1 3S76 3T77 3T77A 9A1 9A2 1121 80 81 82 86 B O W Z Telequipment D56 Telequipment S32A Telequipment D52 S-311 Telequipment TD51 Telequipment S52 Telequipment S51 Telequipment Type A TU-4
6DK6 Vacuum Tube (Pentode) 6DK6 (8136) 154-0149-00 154-0367-00 high-frequency miniature pentode 180 503 513 514 541 543 535 545 545A 551 555
6DQ5 Vacuum Tube (Pentode) 6DQ5 154-0317-00 beam power pentode 560
6DQ6 Vacuum Tube (Pentode) 6DQ6 154-0277-00 power pentode 503 504
6DT5 Vacuum Tube (Pentode) 6DT5 154-0302-00 power pentode 502A
6EJ7 Vacuum Tube (Pentode) 6EJ7 aka EF184  aka 6Ж51П high-gain frame grid RF pentode 526 Telequipment D56 Telequipment S32A Telequipment TD51
6EW6 Vacuum Tube (Pentode) 6EW6 154-0212-00 pentode 132 360 51 527 581 581A 585 585A 3T77 3T77A
6G11 Vacuum Tube (Pentode) 6G11 154-0660-00 double sharp cut-off beam power pentode 125 132 519 067-0502-01 050-0551-00
6GE8 Vacuum Tube (Triode/Pentode) 6GE8 154-0260-00 triode-pentode combo 125 132 560
6GF5 Vacuum Tube (Pentode) 6GF5 154-0494-00 high voltage 9 Watt beam-power pentode 549 556
6GM8 Vacuum Tube (Dual Triode) 6GM8 aka ECC86  aka 6Н27П 154-259 154-0259-00 dual triode 81 516 S
6GV8 Vacuum Tube (Triode/Pentode) 6GV8 aka ECL85 154-0468-00 triode-pentode combo 526 529 RM529
6HZ6 Vacuum Tube (Pentode) 6HZ6 154-0447-00 pentode 526
6J6 Vacuum Tube (Dual Triode) 6J6 aka ECC91 154-032 154-0032-00 high-frequency dual triode 104 104A 161 511 511A 512 517 517A
6KV8 Vacuum Tube (Triode/Pentode) 6KV8 154-497 154-0497-00 triode-pentode combo 3A8
6L6 Vacuum Tube (Pentode) 6L6 154-087 154-0087-00 beam power pentode 511
6M11 Vacuum Tube (Pentode/Dual Triode) 6M11 154-0493-00 pentode and dual triode 556
6SJ7 Vacuum Tube (Pentode) 6SJ7  aka 6Ж8 154-088 154-0088-00 Pentode 511
6U8 Vacuum Tube (Triode/Pentode) 6U8 aka ECF82 154-0033-00 triode-pentode combo 130 160 163 310 315 316 524 535 545 T
6V6 Vacuum Tube (Pentode) 6V6 154-089 154-0089-00 12-watt beam power pentode 511
6W4 Vacuum Tube (Dual Rectifier) 6W4/6W4GT 154-0034-00 dual rectifier 512
6X4 Vacuum Tube (Dual Rectifier) 6X4 aka EZ90 154-035 154-0035-00 dual rectifier 128 130 181 511A 512 517 517A 570
6X5 Vacuum Tube (Dual Rectifier) 6X5  aka 6Ц5 154-090 154-0090-00 dual rectifier 511
6X8 Vacuum Tube (Triode/Pentode) 6X8 154-0036-00 triode-pentode combo
6Y6G Vacuum Tube (Pentode) 6Y6G power pentode 104
7119 Vacuum Tube (Dual Triode) 7119 aka E182CC 154-0340-00 dual triode 067-0532-00 191 3A3 3B4 3B5 516 545B 549 661 Chemtrix 205
7189 Vacuum Tube (Pentode) 7189 aka E84L power pentode
7189A Vacuum Tube (Pentode) 7189A 154-0503-00 power pentode 106
7199 Vacuum Tube (Triode/Pentode) 7199 154-0309-00 triode-pentode 3L10
7233 Vacuum Tube (Triode) 7233 154-307 154-0307-00 low-mu triode 132 506 561 561A 561S 564 565
7247 Vacuum Tube (Dual Triode) 7247 aka ECC832 154-0257-00 dual triode 3C66
7308 Vacuum Tube (Dual Triode) 7308 aka E188CC 154-0371-00 dual triode 3S76 3S3 4S1 4S2A 4S3 S-311
7586 Vacuum Tube (Triode) 7586 154-0306-00 Nuvistor triode M 1A1 1A2 1A5 10A2 10A2A 11B1 11B2A 321 321A 3A1 3A1S 3A3 3A5 3A6 3A7 3A8 3A74 3S76 3T77 3T77A 3B5 4S1 4S2 6R1 6R1A 9A1 9A2 82 86 S-311
7587 Vacuum Tube (Tetrode) 7587 154-0465-00 sharp-cutoff Nuvistor tetrode 184
7693 Vacuum Tube (Pentode) 7693 aka E90F 154-0026-00 154-0285-00 pentode
7699 Vacuum Tube (Dual Tetrode) 7699 dual tetrode 581 585
7734 Vacuum Tube (Triode/Pentode) 7734 154-260 154-0260-00 triode-pentode combo 125 132
7788 Vacuum Tube (Pentode) 7788 aka E810F  aka 6Ж52П (similar) 154-0420-00 long life, shock and vibration resistant pentode 529 RM529 581A 585A RM581 RM585 Telequipment D56
7895 Vacuum Tube (Triode) 7895 154-0378-00 Nuvistor Triode 3B1 3B1S 3B3
8056 Vacuum Tube (Triode) 8056 154-0417-00 low-voltage Nuvistor triode 422 502 W 1S1 3A7 3S3 3T4 5T3 10A1
8233 Vacuum Tube (Pentode) 8233 aka E55L 154-0361-00 special quality 10 watt pentode 3A1 3A1S 3A5 3A6 9A1 9A2
8393 Vacuum Tube (Triode) 8393 154-0461-00 Nuvistor triode 453 454 1A6 1A7 503
8416 Vacuum Tube (Dual Triode) 8416 154-0413-00 157-0116-00 dual triode 1S1 2A61 3A8 3L5 W
8425 Vacuum Tube (Pentode) 8425 154-0022-07 RF pentode 3A72 310A 317 526 Q
8426 Vacuum Tube (Pentode) 8426 RF pentode O 545A 547 549 581A 585A
8608 Vacuum Tube (Pentode) 8608 aka EL5070 154-0491-00 10-watt power pentode 549 556 3A7
CK512AX Vacuum Tube (Pentode) CK512AX 154-0114-00 flat-press subminiature pentode 123
EC1000 Vacuum Tube (Triode) 8254 aka EC1000 subminiature triode P6025 P6032
Y1506 Vacuum Tube (Triode) Y1506 154-0499-00 SHF cermet triode 1L20
Y1641 Vacuum Tube (Triode) Y1641 154-0506-00 154-0510-00 SHF cermet triode 1L20 491