TUBE: TT21 (datasheet covers TT21 and TT22; TT22 = 12.6V/0.8A heater variant)
SOURCE FILE: sheets/084/t/TT21.pdf
MANUFACTURER: GEC / M-O Valve Company Limited (G.E.C., Brook Green Works, London W6 7PE; "The M-O Valve Company Limited")
YEAR: 1973 (February 1973, Issue 3)
PAGES: 24 (pages 1-9 data, page 10 outline/base, pages 11-24 curves)

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THE M-O VALVE COMPANY LIMITED — G.E.C. — TT21 TT22 — BEAM TETRODES
BRIEF DATA: Beam tetrodes suitable for use as r.f. power amplifiers in single side-band or Class C service, as audio amplifiers or modulators. Also useful as pulse modulators and in series and shunt stabiliser service.
Pload (SSB) ........... 110 W
Pload (Class C) ....... 146 W
Pload (Audio, per pair) 140 W

HEATER:                     TT21    TT22
Vh ................. 6.3     12.6   V
Ih (approx) ........ 1.6     0.8    A

MAXIMUM RATINGS (Absolute):       *CCS      †ICAS
Va .................... 1.25      1.25   kV
Va (Ia=0) ............ 3.5       3.5    kV
Vg2 .................. 600       600    V
Vg1 .................. 200       200    V
Pa ................... 37.5      45     W
Pg2 .................. 6         6      W
Pg1 .................. 2         2      W
Ik ................... 230       230    mA
ik(pk) (r.f.) ........ 2         2      A
ia(pk) (pulse) ....... 7.5       7.5    A
Vh-k ................. 150       150    V
Rg1-k (fixed bias) ... 100       100    kohm
Rg1-k (cathode bias) . 220       220    kohm
Tbulb ................ 250       250    degC
*CCS=Continuous Commercial Service. †ICAS=Intermittent Commercial and Amateur Service. Intermittent: 'on' period <=5 min, 'off' period >= 'on' period.

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CAPACITANCES:
Ca-g1 ........... 0.25 pF
Ca-all less g1 .. 13.5 pF
Cg1-all less a .. 17 pF

CHARACTERISTICS:
Va ........ 250   V
Vg2 ....... 250   V
Ia ........ 140   mA
gm ........ 11    mA/V
ra ........ 12    kohm
µg1-g2 .... 8

OPERATING DATA — A.F. Power Amplifier — Class AB1
The TT21 may be used as an alternative to the KT88 in existing audio designs.
Push-Pull. Cathode Bias. Tetrode Connection. (typical):
Va(b) ......... 560   V
Va(o) ......... 521   V
Vg2 .......... 300   V
Ia(o) ........ 2x64  mA
Ia(max sig) .. 2x73  mA
Ig2(o) ....... 2x1.7 mA
Ig2(max sig) . 2x9   mA

===== PAGE 3 =====
(cont. PP Cathode Bias Tetrode):
Rload(a-a) ... 9 kohm; Rk* = 2x460 ohm; -Vg1 ~30 V; Pout 50 W; Dtot 3%; IM 11%; Pa(o) 2x33 W; Pa(max sig) 2x12 W; Pg2(o) 2x0.5 W; Pg2(max sig) 2x2.7 W; Vg1(ac)(pk) 2x30 V. *Two separate cathode bias resistors essential.

Push-Pull. Fixed Bias. Tetrode Connection (typical):
Va(b) 560 V; Va(o) 552 V; Vg2 300 V; Ia(o) 2x60 mA; Ia(max sig) 2x145 mA; Ig2(o) 2x1.7 mA; Ig2(max sig) 2x15 mA; Rload(a-a) 4.5 kohm; -Vg1 ~34 V; Pout 100 W; Dtot 2.5%; IM 10%; Pa(o) 2x33 W; Pa(max sig) 2x28 W; Pg2(o) 2x0.5 W; Pg2(max sig) 2x4.5 W; Vg1(ac)(pk) 2x33.5 V.

===== PAGE 4 =====
Push-Pull. Cathode Bias. Ultra-Linear Connection (40% Tapping Points):
                              (TT21)      (TT22?)
Va,g2(b) ........ 500       375    V
Va,g2(o) ........ 436       328    V
Ia+g2(o) ........ 2x87      2x87   mA
Ia+g2(max sig) .. 2x99      2x96   mA
Rload(a-a) ...... 6         5      kohm
Rk* ............. 2x600     2x400  ohm
-Vg1(approx) .... 52        35     V
Pout ............ 50        30     W
Dtot ............ 1.5       1      %
IM .............. 4         3      %
Pa+g2(o) ........ 2x38      2x28.5 W
Pa+g2(max sig) .. 2x17      2x16   W
Vg1(ac)(pk) ..... 2x52      2x35.5 V
Zout ............ 4.8       4.5    kohm
*Two separate cathode bias resistors essential.

A.F. Power Amplifier and Modulator — Class AB1 — Fixed Bias (Tetrode Connection):
Max Permissible CCS: Va 1.25 kV; Vg2 600 V; Pa 37.5 W; Pg2 6 W.
Typical Operation (various signal levels):
Va(b) ... 1000  1000  1000  1000  V
Va ...... 996   993   990   989   V
Vg2(b) .. 300   300   300   300   V
Vg2 ..... 300   300   299   298   V
-Vg1 .... 40    40    40    40    V
Vg1(ac)(pk) 2x0 2x16 2x25.5 2x32 V
Ia ...... 2x35  2x55  2x79  2x90  mA
Ig2 ..... 2x0.5 2x1.2 2x4.5 2x11.5 mA
Pload ... 0     40    100   140   W
Rload(a-a) 16.8 16.8  16.8  16.8 kohm
D ....... 1.25  1.5   ...   4.8   %

===== PAGE 5 =====
(modulator note: Application Report No. 17; convenient for use with TT21 with anode and screen modulation, modulator and r.f. stage from common 1000V h.t. supply.)

R.F. Power Amplifier — Class C Telegraphy:
Max Permissible Conditions:    CCS      ICAS
Va ......... 1.25      1.25   kV
Vg2 ........ 600       600    V
-Vg1 ....... 200       200    V
Ia ......... 200       200    mA
Pa ......... 37.5      45     W
Pin ........ 200       220    W
Pg2 ........ 6         6      W
Pg1 ........ 2         2      W
Typical Operation — CCS (measured at 30MHz):
Va ....... 500   800   1000  1250  V
Vg2 ...... 300   300   300   300   V
-Vg1 ..... 90    90    90    90    V
Ia ....... 192   182   175   160   mA
Ig2 ...... 20    20    20    20    mA
Ig1 ...... 8.5   7     5.5   4.5   mA
Pa ....... 37.5  37.5  37.5  37.5  W
Pg2 ...... 6     6     6     6     W
Pout ..... 58.5  108.5 137.5 162.5 W
Efficiency 61    75    78    81    %
Rload .... 52    95    115   132   W(ohm-equiv)
Pout(driver) 2.1 1.9   1.8   1.6   W

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Typical Operation — ICAS (Class C Telegraphy, at 30MHz):
Va ....... 500   800   1000  1250  V
Vg2 ...... 300   300   300   300   V
-Vg1 ..... 90    90    90    90    V
Ia ....... 200   200   190   175   mA
Ig2 ...... 20    20    20    20    mA
Ig1 ...... 9     9     7.5   6     mA
Pa ....... 40    43    45    45    W
Pg2 ...... 6     6     6     6     W
Pout ..... 60    117   145   174   W
Efficiency 59    74    76.5  79.5  %
Rload .... 52    103   126   146   W(ohm-equiv)
Pout(driver) 2.1 2.1   2     1.9   W

R.F. Power Amplifier — Class C — Anode and Screen Modulated (Carrier Conditions):
Max Permissible Conditions:    CCS      ICAS
Va ......... 1         1      kV
Vg2 ........ 600       600    V
-Vg1 ....... 200       200    V
Ia ......... 160       180    mA
Pa ......... 25        30     W
Pin ........ 130       150    W
Pg2 ........ 6         6      W
Pg1 ........ 2         2      W
Modulation . 100       100    %

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Typical Operation — CCS (Anode & Screen Modulated, at 30MHz):
Va ....... 550   700   850   1000  V
Vg2 ...... 300   300   300   300   V
-Vg1 ..... 115   115   115   115   V
Ia ....... 160   150   140   130   mA
Ig2 ...... 20    20    20    20    mA
Ig1 ...... 5     3.5   3     2.5   mA
Pa ....... 25    25    25    25    W
Pg2 ...... 6     6     6     6     W
Pout ..... 63.5  80    95    105   W
Efficiency 72    76    80    81    %
Rload .... 54    70    82    87    W(ohm-equiv)
Pout(driver) 1.5 1.4   1.2   1.1   W
Pmod ..... 50    60    68    75    W
Typical Operation — ICAS (Anode & Screen Modulated):
Va ....... 550   700   850   1000  V
Vg2 ...... 300   300   300   300   V
-Vg1 ..... 115   115   115   115   V
Ia ....... 180   175   165   150   mA
Ig2 ...... 20    20    20    20    mA
Ig1 ...... 6.5   5.5   5     3.5   mA
Pa ....... 30    30    30    30    W
Pg2 ...... 6     6     6     6     W
Pout ..... 69    92    110   123   W
Efficiency 70    75.5  78.5  82    %
Rload .... 61    82    94    101   W(ohm-equiv)
Pout(driver) 1.8 1.7   1.5   1.2   W
Pmod ..... 55    68    80    85    W

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R.F. Power Amplifier — Class AB1 — SSB:
Max Permissible Conditions:    CCS      ICAS
Va ......... 1.25      1.25   kV
Vg2 ........ 600       600    V
-Vg1 ....... 200       200    V
Pa ......... 37.5      45     W
Pg2 ........ 6         6      W
Pg1 ........ 2         2      W
Typical Operation:
                CCS     CCS     ICAS
Va ......... 800   1000  1200  V
Vg2 ........ 300   300   300   V
-Vg1 ....... 38    40    45    V
Vg1(ac)(pk) 37    39    44    V
Ia(o) ...... 40    37.5  32.5  mA
Ig2(o) ..... 0.5   0.3   —     mA
Pa(o) ...... 32    37.5  39    W
(two-tone / one-tone columns):
Ia(max sig) ... 86/122  83/130  90/136 mA
Ig2(max sig) .. 4.5/11  5/9     4/8    mA
Pa(max sig) ... 33.5/26.5 34.5/33 47/41 W
Pg2(max sig) .. 1.4/3.3 1.5/2.7 1.2/2.4 W
Pout(mean) .... 35.5/71 48.5/97 61/122 W
PEPout ........ 71  97  122  W
Za ............ 4/4  4.8/4.8  5.5/5.5 kohm
Rload(mean) ... 32/64 43.75/87.5 55/110 ohm
PEPload ....... 64  110  W
D3 ............ 36  33  29  dB
D5 ............ 49  46  43  dB
(Application Report No. 15 describes complete linear amplifier.)

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Pulse Modulator Service:
Max Permissible Conditions: Va 3.5 kV; Vg2 600 V; -Vg1 200 V; Pa 37.5 W; Pg2 6 W; Pg1 2 W; ia(pk) 7.5 A.
Typical Operation: Va 3.5 kV; Vg2 600 V; -Vg1 150 V; Vg1(pulse) 380 V; ia(pulse) 6 A; ig2(pulse) 2.1 A; ig1(pulse) 2.3 A; Ra 460 ohm; tp 2 µs; PRF 1500 p/s.
INSTALLATION: mount vertically or horizontally; tube centres >=100mm, pins 4 & 8 in line. Bulb temp under worst conditions must not exceed 250 degC.
OPERATING NOTES: grid stopper resistor (up to 10kohm in Class AB1, ~100 ohm r.f.), anode stopper 100 ohm 1/4W overwound with 2.5 turns 18 swg copper wire.

===== PAGE 10 =====
OUTLINE AND BASE CONNECTIONS:
Octal base (B8-O). Dome top tubular bulb. Top cap: CT2 anode. 9,14 dia nom cap. 52 dia, 116 (seated), 131 (overall), 43 (base width). Dimensions in mm, maximum.
Base pinout (bottom view):
pin1=bp(base shell); pin2=h; pin3=NP; pin4=g2; pin5=g1; pin6=NP; pin7=h; pin8=k+bp; cap=a
[Reading from diagram: g2(4), a(top cap), g1(5), NP(3), NP(6), h(2), h(7), bp/base shell(1), k bp(8). Side view: a(cap), bp, g2, g1, k, h, h]

===== PAGE 11 =====
ANODE CURRENT — ANODE VOLTAGE, Vg2=300V, with grid voltage as parameter (Vg1 +30 to -30V) [courbes seules — pas de données tabulaires]

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SCREEN CURRENT — ANODE VOLTAGE, Vg2=300V, grid voltage as parameter [courbes seules]

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GRID CURRENT — ANODE VOLTAGE, Vg2=300V, positive grid voltage as parameter [courbes seules]

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ANODE CURRENT — ANODE VOLTAGE, zero grid voltage, screen voltage as parameter (Vg2 200-600V) [courbes seules]

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SCREEN CURRENT — ANODE VOLTAGE, zero grid voltage, screen voltage as parameter [courbes seules]

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CONSTANT ANODE CURRENT CURVES, Vg2=300V [courbes seules]

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CONSTANT SCREEN CURRENT CURVES, Vg2=300V [courbes seules]

===== PAGE 18 =====
CONSTANT GRID CURRENT CURVES, Vg2=300V [courbes seules]

===== PAGE 19 =====
ANODE CURRENT — ANODE VOLTAGE, Vg2=600V, positive grid voltage as parameter (to +300V, Ia to ~8A) [courbes seules]

===== PAGE 20 =====
SCREEN CURRENT — ANODE VOLTAGE, Vg2=600V, positive grid voltage as parameter [courbes seules]

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GRID CURRENT — ANODE VOLTAGE, Vg2=600V, positive grid voltage as parameter [courbes seules]

===== PAGE 22 =====
CONSTANT ANODE CURRENT CURVES, Vg2=600V [courbes seules]

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CONSTANT SCREEN CURRENT CURVES, Vg2=600V [courbes seules]

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CONSTANT GRID CURRENT CURVES, Vg2=600V [courbes seules]. Footer: The M-O Valve Company Limited, Brook Green Works, London W6 7PE. Printed in England.