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SOUND PICTURES
LESSON NO. P-1+

tecnologia cine


THEATER SOUND EQUIPMENT
THE PURPOSE OF THIS LESSON IS TO FAMILIARIZE YOU HITH THE VARIOUS
AMPLIFIER CIRCUITS AND SYSTEM HOOK-UPS AS USED IN THE CONVENTIONAL
THEATER-
YOU HILL FIND THE FIRST PART OF THIS PARTICULAR LESSON TO BE BASED
UPON WESTERN ELECTRIC EQUIPMENT HHICH IS MANUFACTURED AND INSTALLED BY
ELECTRICAL RESEARCH Pnooucrs, Inc. Nesrsnu ELECTRIC EQUIPMENT as VERY
POPULAR IN THE SOUND PICTURE FIELD; AND CAN BE USED HITH ALL TYPES OF
WELL KNOWN PROJECTORS- THE LATTER PORTION OF THIS LESSON I5 DEVOTED TO
0
5%!-

PAGE 2 souuo PICTURES
R.C  PHOTOPHONE SOUND EQUIPMENT AND WHICH ALSO IS USED A GREAT DEAL.
DURING THE FEW YEARS wE HAVE HAD SOUND MOTION PICTURES, PRACT!C-
ALLY ALL souun SYSTEMS vznz DEVELOPED HERELY WITH THE IDEA or souuo RE-
PRODUCTION IN MIND, GIVING LITTLE OR no CONSIDERATION To THE quAL|Tv OF
souuo PRODUCED. UNTIL REcEuTLY,A SERVICE ENGINEER wAs CALLED unou To R5
PAIR souuo EQUIPMENT wusuzvsn TROUBLE OCCURRED- Tans wAs VERY EXPENSIVE
AND LED To MANY DELAYS AND POOR PERFORMANCE. THE PUBLIC NOV DEMAND$ THE
BEST |~ BOTH EQUIPMENT AND OPERATORS, IT |s FOR THIS REASON THAT we ARE
anvnne YOU A THOROUGH TRAINING vu SOUND'AND REPRODUCTION. BEFDRE we
TAKE UP THE PRACTICAL woax AND TRAlN|NG,|T IS NECESSARY TD ACQUAINT YOU
w|Tu THE DIFFERENT SYSTEMS AND EQUIPMENT USED an MOTION PICTURE WORK-WE
SHALL START WITH WESTERN ELECTRIC EQUIPMENT, s|v|ns YOU A BRIEF DESCRI-
_ PTION AND DISCUSSION
LESSON NO-
L PAGE 3
THIS ILLUSTRATION VERY CLOSELY, YOU WILL DISCOVER MANY IMPORTANT FACJS.
FIRST, YOU HILL FIND THAT AT LEAST THO PROJECTORS IAIITH BUILT-IN P.t.
CELL AMPLIFIERS ARE REQUIRED IN ORDER TO OBTAIN CONTINUITY OF REPRODUC-
TlON- A METHOD OF SWITCHING THE OUTPUT OF EITHER MACHINE T0 THE I-I-IA ,A_h_1_


PAGE R SOUND PIcTuRE§
IN us: AND A REcTIrIER wHEN THE AL.PowER SUPPLY Is IN usE. IN THIS IN-
sTALLATIoN, wE FIND THAT A D.C. POTENTIAL Is REquIREo FOR THE EXCITING
LAMP, PHOTO—ELECTR|C CELL, FIELD MAGNETIZING cuRRENT FOR THE LOUD sREA5
ERs, AND FOR THE MIA AMPLIFIER wHIcH Is COMPLETELY_D-C- OPERATED. WE AL
so FIND THAT A D.C. PQTENTIAL FOR THE REA AND U}A AMPLIFIERS Is REQUIR:
ED.
TRACING THE SIGNAL
BEFORE BREAKING THE BLOCK DIAGRAM DOWN INTO ITS COMPONENT PARTS,
LET US TRACE OUR SIGNAL THROUGH THIS COMPLETE S‘fSTEM-
THE HEAVY BLACK LINES IN FIO.I INDICATE "s|aNAL LINES". STARTING
AT THE LEFT’WE FIND THE OUTPUT or oNE FILM PICKUP AND oNE MAGNETIC RE-
105-O
IN THE THEATER. IN F|G- 2 YOU WILL FIND A PHOTOGRAPH 0; THE AMPLIFIERS
AND CONTROL SYSTEM .
P.E. CELL AMPLIFIERS
THE WEsTERN ELECTRIC SYSTEM uszs Two DIFFERENT
EcTRIc CELL AMPLIFIERS. THE OLDER TYPE MACHINES USED
TUBE BEING LOCATED IN THE CELL HOUSING AND THE OTHER
SUSPENDED ON THE MACHINE AT SOME coNvEN|ENT POINT.
IN CONNECTION WITH
PLIFIER wE BUILD up
THE SIGNAL CURRENT
THROUGH THE HZA AND
UjA AMPLIFIERS, THUS
SECURING SUFFICIENT
AMPLICATION or Wyoua
SlGNAL- OuR AMPLI-
FIED SIGNALTHEN GOES
Te THE OU??UT ca»-
TROL PANEL,WHERE IT
Is FED To THE VAR-
Ious LOUD SPEAKERS
TYPES or RuoTo-EL-
THREE STAGES, oNE
Two STAGES BEING
THE NEWER MODELS
USE ONLY TWO STAGES AND BOTH OF WHICH ARE SUSPENDED BELOW THE CELL HOU§
ING-
THE P.E. CELL AMPLIFIER uszo WITH THIS LATTER SYSTEM '5 THE



LESSON no U PAGE 5
D-859k} OR D~86Y29 AND ITS DIAGRAM APPEARS IN FlG- 3- UPON LOOKING AT
THIS oIAsRAM,vou WILL FIND THAT THE P.E. CELL I5 RE$|5T*"°E'°*P*¢'T*
COUPLED TO THE FIRST STAGE. Tu: ACTIVE SURFACE or THE CELL, wH|cH Is Tu:
FILM ON THE INNER SURFACE OF THE GLASS IS CONNECTED T0 THE MINUS SIDE OF
THE BATTERY AND THE COLLECTOR RING Is couuscrso THROUGH A TWO MEGOHM as-
SISTOR TO B PLUS. ALL STAGES EMPLOY rue W.E. 239 TYPE TUBE AND THE FIL-
AMENTS ARE WIRED IN sznnss. THE OUTPUT FEEDS INTO A 500 own LINE WHICH
CONNECTS TO THE FADER.
A CIRCUIT DIAGRAM or THE kl-A AMPLIFIER APPEARS In FIG. 3-
BY REFERRING T0
FIs.2 AeAI~,You WILL W
NOTICE THAT THE REA
AMPLIFIER Is MOUNTED
DIRECTLY BELOW THE HIA
AMPLIFIER, THIS NZA A!
PLIFIER CONSISTS or A
SINGLE TRANSFORMER cog
PLED PUSH-PULL OPERAT-
zo STAGE EMPLOYING A
PAIR OF TYPE W.E. 205D
rua:s.(THE CHARACTERIE
TIC or THESE TUBES ARE
cnvzn IN one or YOUR
TUBE cHARTQ.THz F|LA-
MENTS ARE OPERATED on
A.C. FROM STEP—DONN
TRANSFORMERS. PLATE
VOLTAGES ARE OBTAINED
FROM A PAIR or 205D
TUBES WHICH OPERATE As
RECTIFIERS wusn conn-
ECTING THE GRID AND
PLATE or EACH TUBE 10-’
GETHER. Tn|s AMPLIFIER
HAS A GAIN OF 25 D-5-
Anu Is CAPABLE or oc-
LIVERING 2.5 WATTS or
UNDISTORTED ourpur PO!
ER. SEE FIc.5 roa A
CIRCUIT DIAGRAM OF THE
UZA AMPLIFIER.
To PERMIT THE
FILAMENTS TO LIGHT ec-
FQRE THE HIGH PLATE
VOLTAGE Is APPLIED TO
THE TUBES,THE CONTROL
SWITCH Is szr so THAT
ITS FIRST POSITION,
rue POINTS A-B AND D-E
ARE CLOSED,THUS LIGHT-
ING THE FILAMENTS or
THE 742-A AMPLIFIER
m SWIYCH FOR AR
_ nzsuun Ann UICIIR
Q [HERSHEY gymuils
IIIPUT
SPEAKER VOLUME CONWOL
MULYI-TAPPED MD IMPEDANCE MARI‘
AUTDYIAIISFORHII YA? SWIYClI.$
F01} EXIHIN.


PAGE 6 souuo PICTURES '
THE TUBES. AFTER THE FILAMENTS ARE HOT, THE CONTROL IS MOVED TO POSI-
TION NUMBER TVO AND THE AMPLIFIER THEN GOES INTO OPERATION
THE h3A AMPLIFIER
Tu|s AMPLIFIER us SIMILAR T0 tn: REA, AND CONSISTS OF A SINGLE
TRANSFORMER COUPLED PUSH-PULL STAGE. THIS AMPLIFIER USES Two 211E TYPE
TUBES, snvnnc A PowER output or ABOUT 12 wArrs, 0R A GAIN or 6 D.B. IT_


LESSON No R PAGE Y
AMPLIFIER IS SHOWN IN FIG-6A AND WE ADVISE YOU TO STUDY IT THOROUGHLY
BEFORE CONTINUING WITH THIS LESSON-
OUTPUT CONTROL PANEL
THE OUTPUT or THE U§A AMPLIFI-
ER GOES To THE 200A CONTROL PANEL
TH|s UNIT rs THE DISTRIBUTING SYSTEM
ANo us sHowN AT THE TOP OF THE RACK
IN F|e.2 A REAR-v|Ew or THE 200A
CONTROL PANEL |s sHowN IN FIGURE 6B.
THE PRINCIPLE PART or THIS coN
TROL PANEL coNs|sTs or A sTER-oowN
AUTO-TRANSFORMER WITH A NUMBER or IN
TERMEDIATE TAPs, wH|cH ARE coNNEcTEE
TO sEvEN DIAL sw|TcHEs. TH|s PERMITS
THE CONTROL OF sax SPEAKERS AND oNE
MONITOR SPEAKER- THE MONITOR SPEAKER ;¢_.
HAS A PAD WHICH DROPS THE'POw£R ’ To ““‘“ " ’ ”'*
A COMFORTABLE HEARING VALUE.
Fza. 9
The It/.5. 49-A Amp//'7‘/'¢r
OTHER W.E. INSTALLATIONS
THERE ARE SEVERAL OTHER cou-
PLETE WEsTERN ELEcTR|c INSTALLATIONS
usEo FOR VARIOUS PuRRosEs. ONE or THE|R PRODUCTS, THE h6A sYsTEH, |s
VERY POPULAR AND uszo EXTENSIVELY IN THE SMALLER THEATERs. FoR THE LAR
GER sHow HOUSES THERE IS A cHo1cE or SEVERAL INSTALLATIONS, EACH BUILT
UP FROM STOCK AMPLIFIERS- THEsE srocx AMPLIFIERS ARE THE 8B,9A AND IOA


PAGE 8 SOUND PICTURES
THE 119A AMPL lT>'|ER
Tn: U9A, A new HIGH-GAIN AMPL|F|zR,HAs azzn BUILT FOR use WITH
THE h6A AMPLIFIER. IT uses THE 3A PHOTO—ELECTRlC CELL AND Two STAGES or
W.E. 26hA Tuacs. THE 59A IS usso BETWEEN THE PHOTO—ELECTRIC CELL AND
THE MAIN VOLTAGE AMPLIFIER. |T us MOUNTED |n A RUBBER cusnnonco CRADLE

LESSON No.14 PAGE 9
ES OPERATING AT A PLATE VOLTAGE OF 350 VOLTS AND A anon VOLTAGE or -21
voLTs._lT HAS A GAIN or 16 D.B. AND WILL PRODUCE 1.36 WAYTS or uNo1sTQ3
TED woven. OTHER FEATURES or THIS AMPLIFIER AR: SHOWN IN THE CIRCUIT
DIAGRAM or F1s.12.
THE 10A AMPLIFIER
THIS I5 A HIGH-POWER AMPLIFIER USING FOUR 211E TUBES IN A SINGLE
PUSH-PULL STAGE, OPERATING AT A PLATE POTENTIAL OF 150 VOLTS raom A
sPccrAL RECTIFIER on MOTOR GENERATOR,AND A ennu a|As or -36 VOLTS QB-
TAINED FROM BATTERIES. A BLOCK DIAGRAM or A nzcn POWER INSYALLATION qg
ING vac 8B AND 10A AMPLIFIERS IS suowu IN FIGURE I}. Tn: SAME svsrcm
IN RACK AND PANEL roan us suowu IN F!GURE IN.
<(I|1—\uu
   n H I ! __
Lag/cuf of M E. Sauna’ Prafecfar S5/$7‘e/-r1
THE 6000A RECTIFIER
THIS as THE UNIT THAT SUPPLIES THE PLATE AND FILAMENT VOLTAGE roa
THE LARGE INSTALLAT|ONS- As MAY as scan FROM FIGURE 1%, IT CONSISTS or
THREE QISTINCT PANELS, WHICH ARE THE 519A, on FILTER UNIT FOR Tn: HIGH
voLrAcg RECTIFIER 520A,ANo THE PANEL CONTAINING THE PLATE cunnsur MET-
cas. _
TH: 520A PANEL SUPPLIES 1§0;}50; AND 150 VOLTS FOR THE VARIOUS A5
PLIFIERS. I1 EMPLOYS "Two TYPES W.E. 219 RECTIFIER ruazs IN A FULL-
wAvs RECTIFYING CIRCUIT. A runs: POSITION sw|1cn ENABLES THE FlLA-
MENTS or ALL TUBES TO LIGHT acroaz THE PLATE VOLTAGE IS APPLIED.
FILAMENT VOLTAGE roa THE vAR|ous AMPLIFIERS |s OBTAINED rnom THE
521A PANEL WHICH ls ONLY A STEP-DOHN TRANSFORMER FOR EITHER 110 on 220
VOLTS A.C. THIS PANEL ALso CONTAINS A METER FOR MEASURING FILAMENT cug
RENT.



PAGE IO
SOUND PICTURES
W.E. MISCELLANEOUS EQUIPMENT
THERE IS STILL ANOTHER VERY IMPORTANT ITEM To COMPLETE oun INSTA-
LLATION, AND THAT Is THE FADER. FIGURE 15 sHows A FRONT vIEw or THE
FADER AND FIs.16 A cIRcuIT DIAGRAM. BY STUDYING THE D|AGRAM You wILL
FIND THAT THIS FADER Is A D.B. VOLUME CONTROL THAT wILL ATTENUATE THE
SIGNAL rnom Two CHANNELS- THE RESISTANCE NETWORK on THE INPUT AND ouT-
PuT SIDES or THE FADER ARE H PADS.
SOUND HEAD
THE SUBJECT OF THE SOUND HEAD WAS TAKEN UP IN A PREVIOUS LESSON,
BUT TO MAKE OUR DISCUSSION COMPLETE WE ARE SHOWING YOU THE w.E- SOUND
HEAD IN FIGURE I7. BY LOOKING AT THIS PICTURE HE CAN TRACE THE PATH OF
T (— _ THE FILM THROUGH THE PROJECTOR
5I9~A FILTER
PANEL
A-STAGE :1-1:2
B'SIAGl 3
B"! AHPLIFIR
PLAY! SUM.‘
SWITCHES
' 5201 n:cTIr|E|=
PIN EL
SZITA FILAHEIIY
SUPPLY PA|\U~
I AND suuuu HEAD. NOTICE THE
,§§mR ‘ scnzws on THE EXCITING LAMP
vHIcH ENABLE one To ADJUST THE
‘ LAMP TO ANY DESIRED POSITION-
R.C.A. PHOTOPHONE
SOUND EQUIPMENT
BOX
LIKE THE ELEcTRIc RE-
SEARCH Pnooucrs Co., THE R.C.A
PHoToPHoNE Co. BUILDS AND IN-
STALLS SEVERAL TYPES or souno
°§P SYSTEMS. THEsE ARE CLASSIFIED
""“ INTO THE A TYPE, wH|cH Is no
LONGER MANUFACTURED, THE B syg
TEM WHICH IS uszn FOR HOUSES
OF 2,500 on MORE SEATS AND THE
FUNDAMENTAL UNIT FOR THE SMALL
ER INSTALLATIONS svcn AsC svq;
TEM FOR HousEs BETWEEN 800 AND
MUgm:§MMT‘ 2,500; D SYSTEMS FOR HOUSES OF
800; F SYSTEMS FOR HOUSES or
”700; AND G SYSTEMS FOR HOUSES
OF 500 on LESS. Anonc THE NE!
E51 R,¢ A,|NsTALLATIoNs IS THE
HIGH FIDELITY souuo SYSTEM
WHICH WILL aE oIscussE0 on THE
I FOLLOWING PAGES. ALL or THEsE
‘I usu svsvzms OPERATE FROM THE
A.C. POWER SUPPLY LINE.
TYPE A AMPLIFIERS
THE TYPE A AMPLIFIER IS
A VERY LARGE UNIT, CONSISTING
I-v or Two COMPLETE SYSTEMS 'lN
1=;¢.,.14 mans, s|oE av sIoE, AS suown
7776 Com /e7¢e pane/. IN FIG. I8. THE AMF'I_IFIER$
P WOULD BE IDENTICAL WERE IT NOT



LESSON No.U PAGE I1
FOR ONE RACK WITH A LOUD SPEAKER DISTRIBUTING PANEL ON IT.
VOLTAGE AMPLIFIERS
UNLIKE OTHER SYSTEMS THE R.C.A.PHOTOPHONE EQUIPMENT uozs NOT us:
SPARE EICITER LAMP5
FADER
TOME ccNTR¢L.
FIG.15'
735 Fiaczrt
ARE JUST ADDITIONS OR
THE SOUND HEAD
BY STUDYING Fne.
I9 vou WILL NOTICE now
THE FILM ls THREADED
IN A SIMPLEX MACHINE
AND THE PARTS THAT
MAKE UP THE souuo HEAD.
Tues: PARTS CONSIST or
THE EXCITER LAMP, THE
P.E. CELL, THE souuo
GATE, THE LENS SYSTEM,
THE ROLLERS, AND THE
CONSTANT SPEED SPROCK-
ET5. Fen THE OPERA-
TION OF THE VARIOUS
PARTS, REFER To THE
PRECEDING LESSONS.
A HEAD AMPLIFIER, on P.E. CELL AMPLIFIE&
As IT IS CALLED. THE P.E. CELL IS TRANS-
FORMER—COUPLED To A STAGE USING A UX-210
TUBE AND THEN INTO A UX-8M1 TUBE AND FIN-
ALLY INTO A 210 As THE LAST STAGE. GRID
VOLTAGE us OBTAINED FROM new BATTERIES
AND PLATE VOLTAGE FROM A VOLTAGE TAP ow
THE 1000 VOLT D.C. GENERATOR.
POWER AMPLIFIER
THIS AMPLIFIER, WHICH IS DRIVEN av
A VOLTAGE AMPLIFIER, CONSISTS or A PUSH-
PULL STAGE EMPLOYING TEN UV-8H5 TYPE Tus-
ES. IT OBTAINS PLATE AND GRID VOLTAGE
FROM D.C. GENERATORS. As THIS |s AN OLD
INSTALLATION, we WILL LEAVE IT AND STUDY
THE NEW TYPES or souuo SYSTEMS.
TYPE B EQUIPMENT
VERY CAREFULLY As THE OTHER INSTALLATIONS
. L-
TAGE IS OBTAINED FROM A FUL£
WAVE RECTIFIER EMPLOYING TY-
PE BI Tuezs. Tfie I4/.E. Sou/10' /‘/E50’
BY LOOKING AT Fla. 21
vou CAN FORM A coco MENTAL
PICTURE or THE CIRCUIT DIA-
GRAN. THE g;RsE_ REC-
TIFIER SUPPLIES THE VOLTAGE
AND CURRENT FOR THE MAGNETI-
ZING OF THE SPEAKER FIELDS.
TYPE C SYSTEM
THIS INSTALLATION con
SISTS OF THE SAME VOLTAGE
AND POWER AMPLIFIERS THAT
ARE USED IN TYPE B SYSTEMS,
EXCEPT ONLY TWO POWER AMP-
LIFIERS ARE USED.
TYPE D SYSTEM
TH|s SYSTEM |s ALMOST
IDENTICAL To THE TYPE C sys-
TEH, THE ONLY DIFFERENCE BE-
nnc THAT TYPE D EMPLOYS ONLY
one VOLTAGE AND POWER AMPL|—
FIER, AND IT noes NOT EMPLOY
THE TONE COMPENSATION THAT
|s USED |n TYPE C.
TYPE F AMPLIFIERS
FI6.17

PAGE In souun PICTURES
USED IN OTHER HEADS HAS BEEN REMOVED THE.OPTICAL SYSTEM HA5 ALSO BEEN
SIMPLIFIED. THE MECHANICAL SLIT HAS BEEN MOVED TO THE REAR END OF THE
OPTICAL SYSTEM, AND ADJUSTMENTS ARE MADE AT THAT POINT» FOCUSING IS DONE
BY ACONTROL WHICH
Cfrcu/"Es of Pawer Amp/1'7‘/'er,
HIGH FIDELITY SYSTEMS
THE DEMAND FOR HIGH FIDELITY HAs BEEN MET av THE R.C.A.PHoToPHoNE
Co , IN SEVERAL INSTALLATIONS- THEsE SYSTEMS ARE COMPLETELY.A.C. QPERAT
ED AND ARE MOUNTED IN RACK AND PANEL FORM- ALTHOUGH THEY WERE DESIGNED
FOR USE WITH S|MPLEx PROJECTORS, THEY MAY BE OPERATED w|TH OTHER TYPES.
To OBTAIN HIGH FIDELITY, A NEw TYPE SOUND HEAD wAs BUILT AND IS Now
STANDARD EQUIPMENT. .
THE Ps-2h SOUND HEAD
THIS NEW SOUND HEAD IS CALLED THETHOTARY STABILIZERHBECAUSE A RO-
TARY DRUM IS EMPLOYED FOR THE SOUND TAKE-OFF INSTEAD OF THE USUAL GATE.
THE CONSTANT SPEED CONTROL CONSISTS OF A SMOOTH DRUM PULLED BY THE FILM
MOUNTED ON A SHAFT HAVING A LIGHT HOLLOW CASE ON THE OUTER END OF
SHAFT. THIS SHAFT RUNS ON
THE
BALL BEARINGS. INSIDE THE
cAsE IS A FLYWHEEL coNcENT-
nnc VITH THE SHAFT BUT RUNN-
ING on A EALLBEAHTNG so THAT
IT IS ENTIRELY FREE To RD-
TATE AROUND THE SHAFT- THE
cAsE IS THEN FILLED w|TH OIL
-N“
mm»
--..... D...“
TIIZTIHIZ
Oi
TD DAMP OUT THE OSCILLATIONS
WHICH WOULD OCCUR IN THE MO-
TION OF THE DRUM WERE THE
gILEIiL:_=
I
IIl|Hi'I
E =aI
vi. "~"““;: "‘ ‘ E.
FLYWHEEL CONNECTED TO THE
SHAFT. WHEN THE SHAFT IS RO-
TATEo,THE HOLLOW cAsE WILL
F516. 2111
7H5 Tigoz F:.4n@ufijZern



LESSON uo.h PAGE 15
PoTAT:,cAus|ua THE FLYWHEEL TO TURN nu: To THE VISCOSITY or THE OIL
Tnus new souno HEAD IS SHOWN IN Fun. 2“, WITH ALL PARTS LAa:L:o-As THE
MOTOR 1s BUILT INTO THE souuo HEAD CASTING, IT ELIMINATES THE us: or
BELTS OR CHAINS FOR DRIVING PURPOSES-
TYPE PG-}2 SYSTEM
THIS svsrem, IS COMPLETE FROM PROJECTORS To SPEAKERS AND Is usso
ONLY wntu SIMPLE! MACHINES Tu: SYSTEM INCLUDES SEVERAL NOVEL CHANGES
rnon OLDER EQUIPMENT, A SEPARATE zxcnrsn LAMP SUPPLY VOLTAGE,PHOTO—CELL
EQUALIZING POTENTIOMETER, REMOTE VOLUME CONTROLS AND THE NEW souun HEAD
ausr usscn|s:u- A SCHEMATIC DIAGRAM or THE COMPLETE INSTALLATION |s
snow» nu F|e.25. BY STUDY|NG F|e.25, You WILL rnun THAT THE 868 P.E.
CELL |s COUPLED TO THE VOLTAGE AMPLIFIER av AN IMPEDANCE MATCHING TRAN§
FORMER THROUGH THE SWITCHING PANEL AND FADER.
Tn: FIRST STAGE EMPLOYS A TYPE 22h-A TUBE wnncu us RESISTANCE couf
LED To THE 56 TUBE |u THE szcouo sTAs:. THE FILTER UNIT IN THE PLATE
CIRCUIT or THIS STAGE PROVIDES A SHARP CUT-OFF AT 9500 CYCLES. Bv PARA-
LLELING THE 950 MMFD- connsuszn WITH A 550 unro. connzuszn AND CHANGING
TAPs on THE co|L, A CUT—OFF or 1000 CYCLES MAY as HAO. TH: 56 STAGE |s
COUPLED TO A PUSH—PULL STAGE EMPLOYING Two 2N5 TUBES As A VOLTAGE AMPLl
FIER. '
Tn: POWER AMPLIFIER vs A PUSH-PULL STAGE usnua B45 TYPE ruazs. A
PICTURE or oun COMPLETE AHPLIFYING svsrzu MAv as rouun an F:e.26. Tans
AMPLIFIER SYSTEM |s ALSO KNOWN As TYPE PA-52. PLAT: VOLTAGE ron THE vqh
TAGE AMPLIFIER AND POLARIZING VOLTA

LESSON Ho. U PAGE I7
OBTAINED FROM A VELL FILTERED RECTIFIER EMPLOYING A TYPE 80 TuaE. THE
POWER AMPLIFIER REcE1vEs ITS PLATE SUPPLY FROM A HIGH VOLTAGE RECTIFIER
CONTAINING Two TYPE 866 MERCURY vAPoR TUBES. To PREVENT DAMAGE T0 THE
TUBES, A TIME DELAY CIRCUIT PERMITS THE FILAMENT To HEAT UP BEFORE THE
HIGH PLATE voLTAeE IS EMPLOYED.
BECAUSE OF THE HIGH VOLTAGE; EXTREME CARE MUST BE TAKEN T0 PREVENT
PERSONAL INJURY. A SAFETY SWITCH IS CONNECTED IN THE CIRCUIT WHICH TURNS
OFF THE HIGH VOLTAGE, HHENEVER THE COVER-
ING FOR THE POWER AMPLIFIER IS REMOVED.  _,ii

THE EXCITER LAMPS RECEIVE DIRECT
CURRENT FROM SEPARATE DISC RECTIFIERS; amen“
ONE BEING EMPLOYED FOR EACH LAMP. THE “"55
CURRENT IS VERY WELL FILTERED TO OBTAIN
A PURE DIRECT CURRENT.
VOLUME :nnI|0L
OPERATING INSTRUCTIONS lAbV|£:Y.k(;|0s/
To sTART THE EQu|PHEHT,TuRN "DH" ~"w"»“
THE A.C. LINE sw|TcH AT THE ToP OF THE
RACK on: MINUTE BEFORE THE svsTEH IS To
as usED. AFTER 30 SECONDS, THE TIME DE-
LAY APPLIES THE PLATE VOLTAGE To THE
TUBES AND A BLUISH eLou v|LL APPEAR
AROUND THE PLATEs OF THE 866 RECTIFIER  .
TUBES. FIG
AFTER THE MACHINES HAVE BEEN CLEAN— {gar L§gM/ 3/'Ayqp[ £2;k
ED AND o|LED, THREAD THE FILM THROUGH THE
PROJECTOR AND souun HEAD,LEAv|He THE REQUIRED LooPs. TDRH on THE EXCITER
LAHP av THROHING THE sH|TcH on THE BACK or THE souuo HEAD To THE "on"
POSlTl0N- START THE PROJECTOR BY TURNING THE HDTDR sv|TcH T0 THE "on"
POSITION. AFTER THE MOTOR HAs GAINED SPEED (AsouT THO sEcoHDs) FADE THE
souuo c|Rcu|T on THIS PROJECTOR av DEPRESSING AHD RELEAs|He THE FADER
sH|TcH HANDLE on THE souuo CONTROL UNIT- WHEH THE souuo CIRCUIT |s com-
PLETE, THE INDICATOR LAMP on THE CONTROL UNIT HILL LIGHT. THE INPUT cog
TROL UNIT IS NOT USED As THE VOLUME coHTRoL. IHsTEAD, A GAIN CONTROL |s
EMPLOYED FOR EAcH AMPLIFIER AND IS CONTROLLED BY REMOTE CONTROL BUTTONS.
To sToP THE EQUIPMENT; |T IS ONLY NECESSARY To TURN "OFF" THE A.C. LINE
sv|TcH on THE AHPL|P|ER RAcx.
THE PG-65 SYSTEM
_ TH|s as A SMALLER INSTALLATION THAH THE PG-32 EQUIPMENT. IT as
SUITABLE FOR HOUSES HAVING A cAPAc|TT or 800 sEATs. A PS-24 TYPE SOUND
HEAD IS EMPLOYED, THE ouTPuT or wH|cH |s IMPEDANCE MATCHED To THE GRID
OF A 51 TYPE TUBE. THE 57 TUBE |s RESISTANCE couPLED To A 56 TUBE EM-
PLOYING A 500,000 OHM v0LuHE LDHTRDL IN THE GRID CIRCUIT-_ TH|s IS USED
As THE MAIN GAIN CONTROL.
FRQM THE 56 sTAeE, THE SIGNAL FEEDS To Two 56's an A PUSH-PULL
STAGE uH|cH IN TURN DRIVES A PusH-PuLL PowER STAGE or 2A§‘s DEL|vER|H§
APPROXIMATELY IO wATTs or UNDISTORTED POVER- A PANEL HIRING DIAGRAM or
THE AMPLIFYING sYsTEM,KHoHu ALsD As TYPE PA-96Ab as suouu IN Fne. 27.



PAGE I8 souwo PICTURES
PLATE VOLTAGES FOR THE AMPLIFIER AND THE POLARIZING VOLTAGE roa
THE P.E. CELL ARE OBTAINED FROM A FULL HAVE RECTIFIER CONSISTING or Two
TYPE 80 TUBES IN PARALLEL. Tu: STAGE LOUDSPEAKERS ARE cuznerzzo av
usrue THE FIELD COILS AS THE FILTER cnoxzs |u THE RECTIFIER SYSTEM-
TT:::::\21] -%#§$E€1 I55‘:
DIRECT CURRENT FOR THE EXCITER LAMPS I5 OBTAINED FROM A HELL FIL-
TERED DISC TYPE RECTIFIER, ONE BEING EMPLOYED FOR EACH LAMP. A5 THERE
IS NOT SUFFICIENT POWER FROM THE MAIN AMPLIFIER T0 OPERATE A MONITOR
SPEAKER BESIDES THE STAGE SPEAKER$,A SPECIAL POUER AMPLIFIER IS PROVIDED
TO SUPPLY POWER TO THE MONITOR SPEAKER. THIS AMPLIFIER CONSISTS OF A
PUSH—PULL STAGE EMPLOYING H5 TYPE TUBES- THE OPERATING VOLTAGE IS OB-
TAINED FROM A 80 TYPE RECTIFIER; WHICH TOGETHER HITH THE AMPLIFIER STAGE
AND SPEAKER IS MOUNTED IN A STEEL CABINET- THE OPERATING VOLTAGE AND
CURRENT ARES
GRID Scnszn PLATE PLATE FILAMENT
THE TOTAL PLATE CURRENT DRAIN IS ABOUT IMO MlLL|AMPERES- THE Fl-
DELITY CURVE axrzuos FROM 50 TO I0,000 CYCLE$- THE AMPLIFIER I5 counsel
so wuzu BUILT so THAT IT covzas THE RANGE HITH A RISING CHARACTERISTIC
TO 5000 CYCLES AND THEN onops OFF AT 5000 CYCLES. THIS cuavz MAY as
VARIED sv MAKING nunon CIRCUIT CHANGES, A FLAT RESPONSE asaue oaTA:~"



LESSON Mo. A PAGE I9
WHEN THE BYPASS CONDENSER ACROSS THE BIAS RESISTORS or THE FIRSW THO
STAGES IS REMOVED. A SLIGHT RISE UP T0 3000 CYCLES MAY as HAD av SHUNT-
ING THE BIAS RESISTOR 0F THE szcouo STAGE WITH A .I MFD CONDENSER AND
l,OO0 OHM RESISTOR IN SERIES. HIGH FREQUENCY RESPONSE MAY a: OBJAINED
av SHORTING OUT RESISTOR R-27, on REMOVING tn: BYPASS CONDENSER FROM THE
BIAS RESISTOR or THE SECOND STAGE AND SHUNTING THE 57 Tuaz's BIAS RESIS-
TOR WITH A .2 MFD counsussn. AM INCREASE IN Low FREQUENCY RESPONSE MAY
BE OBTAINED BY REMOVING tn: 60,000 OHM RESISTOR R-32 AND R-3} IN THE
GRID CIRCUIT OF THE 2Aj's.
TABLE I
CHARACTERISTICS OF WESTERN ELECTRIC TUBES
_ I , I , , I I _ -.
PLATE PLATE FILAMENT FILAMENT PLATE I Buns I
VOLTAGE CURRENT VOLTAGE CURRENT Mu. RESISTANCE VOLTAGE
—ro;-5 4:--—
WESTERN ELECTRIC TUBES
IN TABCE I YOU ARE GIVEN THE MORE IMPORTANT OPERATING CHARACTERIS-
TICS OF THE MOST POPULAR SERIES OF WESTERN ELECTRIC TUBES.
FROM WHAT YOU HAVE ALREADY LEARNED FROM YOUR PREVIOUS STUDIES IN
THIS COURSE, YOU SHOULD EXPERIENCE NO DIFFICULTY IN ACQUIRING A GOOD
UNDERSTANDING OF THE EQUIPMENT WHICH IS DESCRIBED IN THIS LESSON. MUCH
OF THIS SOUND PICTURE AMPLIFYING EQUIPMENT IS IDENTICAL TO THAT USED FOR
OTHER PURPOSES,VlTH CERTAIN CHANGES AND ADDITIONS UHICH SERVE TD BEST
ADAPT IT TD SOUND PICTURE WORK-
J. A. ROSENKRANZ
DRAW A DIAGRAMMATIC SKETCH WHICH ILLUSTRATES THE LAY-
OUT OF THE SOUND PICTURE EQUIPMENT IN A TYPICAL THEATER
NAMING ALL OF THE VARIOUS UNITS-
DESCRIBE A WESTERN ELECTRIC SOUND INSTALLATION FOR A
MOTION PICTURE THEATER-
DESCRIBE AN R.C.A. PHOTOPHONE souno INSTALLATION FOR A
MOTION PICTURE THEATER.
MAKE A SKETCH OF A TYPICAL SOUND HEAD AS EMPLOYED ON A
MOTION PICTURE PROJECTOR AND NAME ITS PARTS.
DESCRIBE some OF THE MORE IMPORTANT FEATURES or THE 43A
WESTERN ELEcTRIc AMPLIFIER.
EXPLAIN How YOU wouLn OPERATE THE TYPE PG-32 PHOTOPHDNE
EQUIPMENT.
NHAT ARE THE OPERATING CHARACTERISTICS OF son: or THE
MORE IMPORTANT TYPES OF WESTERN ELECTRIC TusEs?
DRAW A CIRCUIT DIAGRAM OF THE M6-A WESTERN ELECTRIC
AMPLIFIER AND EXPLAIN How IT Is USED.
DRAW A CIRCUIT DIAGRAM or THE R.C.A. VOLTAGE AMPLIFIER-

DRAw A CIRCUIT DIAGRAM or THE R.C.A. POWER AMPLIFIER-

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