Chelmer Valve 738-196 | electronic tube BRIEF DESCRIPTION: This valve is a beam tetrode with metal-shell wafer, octal base designed for use Specifically in the output stage of an audio frequency amplifier. KT88 At reduced power, used in ultra linear mode, push-pull, maximum continuous output of up to 100 watts. Two valves in class AB1 can give a distortion can be limited to 2% at 70 watts or 1% at 30 watts output. HEATER Vpy ccecseecsceeseseeeseseeeerevesscsvenssevesesieneseneeeseeeeseees 6.3. V Upp cecescesescsceeescsescesetecsevacceseaeeeeaesaeeateetateetatiees 1.6 A MAXIMUM RATINGS Absolute Design Maximum Vag eet teeter 800 800 Vv V2 cece er eeceeserereeceenees 600 600 Vv Vag? cosets 600 600 Vv Vat cesseeseeereeeteeee 200 200 V Pa cessseseesteseseeseeeeees 42 35 Ww Pog csecsesseseneseecaterscens 8 6 w Paag? ccsceesceeseeeceeetees 46 40 w Wyo seeeeeeeceeeasaeeeeeren eens 230 230 mA Vie K ccecceecseeeeeeeeeneenee 250 200 Vv Thulb cee e eee ceeeseeeeseeeees 250 250 c Rei-k (cathode Bias) Pa+g2=35W bea eeceeceeeesaseeeneeaeeneneees 470 kQ Paeg?>3SW ceeeeceececsesseseesceeeeeees 270 kQ Rgi-k (fixed bias} Parg2S35W veces ecseeeereeeetes 220 kQ Panga? 35W coeccccccseeesscereeteeeesteees 100 kQ CHARACTERISTICS Tetrode Connected Vag cretet tees sence eee eseeseneeeeceeeserenees 250 Vv Ve2 wet e eee bene ee seee pene eeete tee eneaenee 250 Vv Lg cecetceeeeeseeesceetteeeeeeseneneesessenees 140 mA 199 (:\3)5) (6) 9 3 mA Voi (APPLOX) 2.0... ceeeeeeceece eee eees 15 v Bip cic eeet eect ee eee eeeeeeeeeeeeees eens nenees 11.5 mA/V Tg etc eeceseee ese easeesseaeesceeeecesan ees 12 kQ Hot MEQ crrrretr ese tet eters ese eeeeee ees 8 Vag? bene t eet ne eee ee eee en eeceesnesseeteeeeee 250 v Taig? Seen eee c eee eats eee e sv etna eensenetenes 143 mA Voi C10) 0) 40) 9 1S Vv Bry cere eceece ese eec sen eseneraseceeeenenseeenes 12 mA/V Dy cecceecececeeeeeesseeeseneseeneeeetenenseees 670 Q ice cacs ce ceee cece rece ee eeteeeerseeteeees 8 CAPACITANCES (Measured on a cold unscreened valve) Triode Connection Tetrade Connection Cy1-ag? wees eee ee eee 7.9pF Cola cede eeeeeeeeeeeeoees 1.2 pF Cet-all less ag? 9.3pF Cy all less acc: 16 pF Cag2 all less gl -- 17 pF Ca all less gh ccc 12 pF OUTLINE .Base: Metal shell wafer octal 110 S2dla 125 Pin: 1 base shell 91 2h 6 NP 3 0a 7 Oh 4 g2 8 k.bp Dimensions mm and are maximum TYPICAL OPERATION Push-Pull. Class ABI. Cathode Bias. Tetrode Connection. Va(b) wee ca cee ereveneeeeneoesestteseesens 560 Vv a(O) creer teste tees te eeeete sere eee 521 Vv Vg2 wee b cece eee eee eet enenereeeeeeteae 300 Vv 14(0) cence bela ee eae ee eee eeeeenteeeeeeees 2x64 mA I, (max Sig) ccccrccteee eee 2x73 mA 12(0) feeb eee cse rece eeernaeneeaennapeees 2x1.7) mA 1p2 (max sig) cccccttcet eset 2x9 mA Ri(a-a) cee be ree e cere ee eeeeeneteneenee 9 kQ BR eescccceecececeeesteeeneenrenaees 2x460 Q Voi (Approx) oo... eee eee eee 30 Vv OUL cre trer treet teeta ee eeeeseeeen eens 50 WwW Dot cecceececeeeceeeeeeeteereeeeeenenees 3 % TM icciecccccceeeeeeseeneneeceereres 11 % Pao) eee nnn eee tee e cnet en eea cane 2x33 WwW Pa (max sig) cccrceeeeeeeeeee 2x12 WwW P92(0) Leese ee ee cece neste stance eaee tees 2x0.5 W Po? (max sig) sccccerreeeeeeeeees 2x2.7 W Vigi-gi)(ac) CTESt wo... eee eee ee 60 Vv SF See notes, Page 2. INSTALLATION: The tube may be mounted either vertically or horizontally. When tubes are mounted vertically it is recommended that the centres of the tube sockets are not less than 4 inches apart and that pins 4 and 8 of each tube are in line. directly above another. When tubes are mounted horizontally it is recommended that the centres of the tube sockets are not less than 4 inches apart and that pins 4 and 8 of each tube are in the same vertical line. Free air circulation around the tube is desirable. One tube should not be mounted8 Chelmer Valve KT88& electronic tube Push-Pull. Class AB1. Fixed Bias. Tetrode Connection. Push-Pull. Class AB1. Fixed Bias. (40% Tapping Points) Ultra-Linear Connection. Va(b) cretesiesessesceseceeeeeeneevees 560 V Vag2(b) crrsretstsessesseseeeeeens 560 460 Vv a(0) cetteteseeescseeecseeeeeeeeees 552 V ag2(0) vrritreseseesesseeeeeneeees 553 453 Vv g2 Seen ene een eae sen e meee eee eeenscerne 300 Vv Ta+g2(0) Dee eee tenn eee e co nnteeeee 2x50 2x50 mA lao) saves ee eee teseeaeeeneetenssetstecaes 2x60 mA a+g2 (max sig) stort 2x157 2x140 mA I, (max Sig) ccrctteteteeeeereee erro 2x145 mA Ri (a-a) cece eeeeseeeeteeseseeens 4.5 4 kQ 192(0) cee ne nsec es seaecceceeeeeeeeeeates 2x1.7) mA *-Veq (APPrOx) ....... ee es es eees 78 59 Vv g2 (max sig) sserreseeceeseeeseees 2x15 mA QUE ttetesesteeseseteseesesnseseees 100 70 OW Ri (a-a) cee ta ete ceccerersteeeeesseeceees 4.5 kQ Diot cet eeeesenscceenesenseusereceses 2 2 % *-Ve1 (APPTOX) ...2. eee 34 Vv FEM ooccccceeeceeseseee 11 10 % Pout ceeceseseseseseeeeeeteteteeeeeces 100 32W Paspa(o) crreccesseceeeeeeneseeneens 2x27.5 2x22.5 W Dot vrecccscesseecseeeeeeeeesesteesees 2.5 % Pasg? (max sig) ener 2x33 2x27 W FEM ooeeceececceseeseelesteneceee: 10% Vigi-gi)(ac) CFESt sees 140 114 Vv Pa(o) ceretesesesseeeessesseenetees 2x33 OW UL ceeteeesestaceceseceecaeateesees 7 6.5 kQ Pa (max sig) secs 2x28 = W P2(0) cect bene ececcccccreeesrnteresese 2x4.5 WwW Po? (max sig) crt eee 2x4.5 WwW V(gi-g1)(ac) CKESt oo... ecco ee 67 Vv Push-Pull. Class AB1. Cathode Bias. Push-pull. Class AB1l. Cathode Bias (40% Tapping Points) Ultra-Linear Connection Triode Connection Vag2(b) vo bene eae cereeeereeeeses 500 375 Vv Vag2(b) dc ceeeeeeeeeneeses 400 485 Vv Vag?(0) cee edaeeceeeesseeceeeese 436 328 Vv Vag2(0) sen aeeeeeeeeeenees 349 422 Vv Ta+g2(0) ste beteetaeee eee saneeeaes 2x87 2x87 mA lasg2(a) ste eeeeeeeners eens 2x79 2x94 mA laeg? (max sig) scree 2x99 2x96 mA a+g2 (max sig) ------ 2x80 2x101 mA RU (ga) cece cierto _ 6 5 kQ Riana) ceresereeeees 4 4 kQ a 2x600 2x400 Q -Vo1 (approx) ......... 40 50 Vv Vegi (approx) ...........00.. 52 35 Vv OUL ct etteeeeeeeceeecenees "17 31 Ww Popp ceccsceseeeseeeseeeeesenees 50 30. W Dot ccieeeeeeeetteeeneees 1.5 1.5 % oe 1.5 1 % FEM cette 5.6 5.6 % IM woe eceeeeceseeneeee 4 3 % Paap 2(o) cecceererseeenes 2x26.5 2x40 Ww a+g2(0) Pa+g?(o) deeb ee seeeeeeeeeseeces 2x38 2x28.5 W Pa+g? (max sig) "+ 2x19 2x27 WwW Pasg? (max sig) ve 2x17 2x16 OW Ry eeceesestreesseeteesens 2x525 2x525 Q V(gi-gi Yac) CFeSt ......., 104 71 Vv V(gi-gi)(ac) crest 78 114 - Vv Ut cresteeeeeeeeeecaeneeeeeees 4.8 4.5 kQ UL cceeceseeceececeeesens 2 1.9 kQ * having a voltage adjustment range of 425%. It is essential to provide two seperately adjustable bias voltage sources, t Intermodulation distortion; measured using two input signals at 50 and 6000Hz (ratio of amplitudes 4:1). A It is essential to use two seperate cathode bias resistors. 2/3