TUBE: KT77 SOURCE FILE: sheets/086/k/KT77.pdf FABRICANT: Genalex / The M-O Valve Company Limited (GEC Group) ANNEE: April 1977, Issue 3 LANGUE: en ===== PAGE 1 ===== THE M-O VALVE COMPANY LIMITED - KT77 Genalex - BEAM TETRODE BRIEF DATA A beam tetrode with an absolute maximum anode dissipation rating of 32 watts. The KT77 is designed for use in the output stage of an af amplifier. Two valves in Class AB1 give a continuous output of over 70 W. The KT77 is also suitable for use as a series valve in a stabilised power supply. HEATER Heater voltage ......... 6.3 V Heater current (approx) . 1.4 A MAXIMUM RATINGS Absolute Design Max. DC anode voltage ............. 850 800 V DC screen voltage ............ 650 600 V DC anode and screen voltage .. 650 600 V Anode dissipation ............ 32 25 W Screen dissipation ........... 6.0 6.0 W Anode and screen dissipation . 35 28 W DC cathode current ........... 200 180 mA Heater-cathode voltage ....... 200 150 V Negative dc grid voltage ..... 220 200 V Grid-cathode resistor (cathode bias) Pa+g2 <= 28 W .............. 1.0 MOhm Pa+g2 > 28 W ............... 0.5 MOhm Grid-cathode resistor (fixed bias) Pa+g2 <= 28 W .............. 0.5 MOhm Pa+g2 > 28 W ............... 0.25 MOhm Bulb temperature ............. 250 230 degC CAPACITANCES (Measured on a cold unscreened valve) Grid to anode .......................... 1.0 pF (Cga) Grid to all other electrodes, less anode 16.5 pF (Cin/Cgk) Anode to all other electrodes, less grid 9.0 pF (Cout/Cak) A member of the GEC Group of Companies. (c) 1977 The M-O Valve Co. Ltd. April 1977 Issue 3 ===== PAGE 2 ===== CHARACTERISTICS Tetrode Connection DC anode voltage ............. 250 V DC screen voltage ............ 250 V DC anode current ............. 110 mA DC screen current ............ 10 mA Mutual conductance ........... 10.5 mA/V Internal anode resistance .... 23 kOhm Inner amplification factor ... 11.5 Triode Connection DC anode and screen voltage .. 250 V DC anode and screen current .. 120 mA Mutual conductance ........... 11 mA/V Internal anode resistance .... 1050 Ohm Amplification factor ......... 11.5 TYPICAL OPERATION Ultra-linear Connection. 43% Taps. Push-Pull. Class AB1. Cathode Bias Vb ................. 430 V Va,g2 ............. 390 V Rg2 ............... 2x22 Ohm Rk ................ 2x470 +/-5% Ohm RL(a-a) ........... 6.0 kOhm Ia+g2(o) .......... 2x66 mA Ia+g2(max sig) .... 2x80 mA Pa+g2(o) .......... 2x26 W Pa+g2(max sig) .... 2x14 W -Vg1 .............. 31 (approx) V Vin(g1-g1)(pk) .... 69 V Pout .............. 34 W Dtot .............. 2.5 % ===== PAGE 3 ===== Ultra-linear Connection. 43% Taps. Push-Pull. Class AB1. Fixed Bias Vb .............. 600 500 400 V Va,g2 .......... 594 493 391 V Rg2 ............ 2x22 2x22 2x22 Ohm RL(a-a) ........ 9.0 5.5 4.5 kOhm Ia+g2(o) ....... 2x47 2x57 2x70 mA Ia+g2(max sig) . 2x109 2x126 2x121 mA Pa+g2(o) ....... 2x28 2x28 2x27.5 W Pa+g2(max sig) . 2x28 2x28 2x24 W -Vg1 (approx) .. 56 43 31 V Vin(g1-g1)(pk) . 94 82 61 V Pout ........... 72 67 45 W Dtot ........... 1.5 1.0 0.8 % *A bias adjustment range of +/-25% about these values should be available for each valve. Tetrode Connection. Push-Pull. Class AB1 The KT77 is designed primarily for use under ultra-linear conditions and this connection is recommended. However, similar performance can be obtained in the tetrode connected arrangement but the output impedance will be greatly increased. For tetrode connection the fixed screen supply must not exceed 300 V. Triode Connection. Push-Pull. Class AB1. Cathode Bias Vb .............. 430 V Va,g2 .......... 396 V Rg2 ............ 2x22 Ohm Rk ............. 2x440 +/-5% Ohm RL(a-a) ........ 5.0 kOhm Ia+g2(o) ....... 2x69 mA Ia+g2(max sig) . 2x75 mA Pa+g2(o) ....... 2x27 W Pa+g2(max sig) . 2x20 W -Vg1 ........... 30 (approx) V Vin(g1-g1)(pk) . 66 V Pout ........... 18.0 W Dtot ........... 1.2 % ===== PAGE 4 ===== LIFE PERFORMANCE Average life expectancy at absolute max ratings >= 5,000 hours. At reduced rating Pa+g2=25W, life >= 10,000 hours. End of life: Output power < 50% of initial; Mutual conductance < 9.3 mA/V Measured at: Va=250V, Vg2=250V, Ia=100mA. INSTALLATION: any position; free air circulation desirable; valve sockets >= 9cm apart. ===== PAGE 5 ===== BASE CONNECTIONS AND VALVE DIMENSIONS [Octal base, view from underside] pin1=NC ; pin2=h ; pin3=a ; pin4=g2 ; pin5=g1 ; pin6=NP ; pin7=h ; pin8=k,bp (cathode+beam plates) Base: International Octal (B8-0) Bulb: Tubular Max overall length: 113 mm ; Max seated length: 99 mm ; Max diameter: 33 mm [NOTE: beam tetrode - 2 grilles (g1,g2) + plaques de deviation de faisceau (beam plates, bp) reliees a la cathode. PAS de 3e grille suppressor. Construction beam = tetrode a faisceaux dirigés.] ===== PAGE 6 ===== [courbes seules] KT77: Anode plus screen current vs Anode and screen voltage (triode connection), Vg=0 to -40V, Pa=35W ===== PAGE 7 ===== [courbes seules] KT77: Anode and screen currents vs Anode voltage, Vg2=300V, Vg1=0 to -25V, Pa=27.5W ===== PAGE 8 ===== [courbes seules] KT77: Anode and screen currents vs Anode voltage, Vg2=200V, Vg1=0 to -15V, Pa=27W ===== PAGE 9 ===== [courbes seules] KT77: Total distortion vs Output power, ultra-linear 43% taps PP AB1 fixed bias, Vb=400V, RL(a-a)=4.5k ===== PAGE 10 ===== [courbes seules] KT77: Total distortion vs Output power, ultra-linear PP AB1 fixed bias, Vb=500V RL=5.5k and Vb=600V RL=9.0k ===== PAGE 11 ===== [courbes seules] KT77: Total distortion vs Output power; ultra-linear PP AB1 cathode bias Vb=430V RL=6.0k Rg2=2x22 Rk=2x470; triode PP AB1 cathode bias Vb=430V RL=5.0k Rk=2x440