the aa8v wingfoot 813 amplifier

8/14/2019 The AA8V Wingfoot 813 Amplifier

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The AA8V Wingfoot 813Amplifier

High Technology Of The 1950's In The 2000's

y !reg "#tt#$ AA8V

%irc&it escription #n( )chem#tic i#gr#m

Wingfoot 813 Amplifier Pages

Main Page and Front and SideViews

Tank Coil Information

Interior and Bak Views T!pial "perating Conditions

%irc&it escription #n( )chem#tic

i#gr#mPower S#ppl! P$otos

813 T#%e Information Power S#ppl! Cir#it &esriptionand S$emati &iagram

Cir#it &esriptions and S#%'S$ematis

Inp#t Transformer (rid Metering Cir#itMode Swit$Cir#it

Inp#t Cir#it Plate Metering Cir#it Bias Cir#it

Plate Feed Cir#it T) Swit$ing Cir#it813 Beam Power

Tetrode

Plate Tank Cir#it

%lic* On A )ection of the )chem#tic +elo, for Inform#tion on Th#t -#rt of the

%irc&it.
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%lic* here for # high resol&tion schem#tic/

%lic* here for # rot#te( schem#tic more s&it#le for printing/

T$e Wingfoot 813 amplifier was designed and %#ilt %! me to mat$ t$e W8*+IWingfoot VF" *,iter- At t$e time I reei.ed t$e e,iterfrom /im Tr#tko0 W8*+I0 I

also reei.ed an amplifier t$at /im $ad %een working on !ears earlier- &esigned aro#nd

t$e pop#lar in t$e 1245s6 813 %eam power tetrode0 t$e amplifier was #nfinis$ed andinomplete- T$ere was also a power s#ppl! for t$e amplifier on a separate $assis0 %#t t$e

power s#ppl! $ad design pro%lems0 defeti.e parts parti#larl! t$e filter apaitors60 and

was not operational-

Sine t$e amplifier wo#ld make a %ea#tif#l ompanion to t$ee,iter0I deided to repairand redesign t$e power s#ppl!0 and t$en to ompletel! disassem%le t$e amplifier into a

pile of parts and start ompletel! o.er- T$e res#lt is an amplifier of e,eptional

performane and %ea#t!-
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%irc&it esign %onsi(er#tions.

T$e design of t$e amplifier was largel! determined %! t$e parts on $and7 it wo#ld %e

designed aro#nd t$e 813 %eam power tetrodeand wo#ld $opef#ll! #tilie t$e tankomponents on $and- A gro#nded grid at$ode dri.en6 onfig#ration was seleted0 sine

plent! of dri.e was a.aila%le0 and t$e ir#it wo#ld %e simpler- It was deided to r#n t$e

8139triode onneted90 wit$ t$e sreen in parallel wit$ t$e ontrol grid- T$is wo#ldeliminated t$e need for a sreen s#ppl!0 and d#ring operation t$e t#%e o#ld %e r#n wit$

ero %ias- A %ias s#ppl! wo#ld t$#s onl! %e needed to #t off t$e t#%e d#ring

stand%!:reei.e0 and a simple0 #nreg#lated %ias s#ppl! wo#ld s#ffie- T$o#g$ in inp#tmat$ing ir#it wo#ld $a.e gi.en %etter linearit! and a %etter impedane mat$ to some

e,iters0 one was not #sed sine t$e e,iter o#ld mat$ a wide range of impedanes and

t$e amplifier wo#ld %e #sed for CW0 w$ere linearit! was not a ma;or onern- Finall!0

sine t$e amplifier mig$t %e #sed wit$ a transei.er0 a rela! transmit:reei.e ir#it wasinl#ded to %!pass t$e amplifier and appl! #toff %!pass to t$e 813d#ring reei.e-

%lic* here for pict&res #n( inform#tion on the m#tching Wingfoot VO 22

citer

Amplifier Inp&t Tr#nsformer.

T$e inp#t impedane of a gro#nded grid

amplifier is t!piall! se.eral $#ndred o$ms-T$o#g$ most .a##m t#%e transmitters will

$a.e no tro#%le dri.ing s#$ an impedane0

solid state transmitters0 w$i$ are designed todri.e loads t$at are .er! lose to 4 o$ms0 will

#s#all! ref#se to dri.e s#$ a load- T$e %est

and most ompliated6 sol#tion is to #se a

t#ned mat$ing network on t$e inp#t-


4/9

Amplifier Inp&t #n( il#ment )&pply

%irc&it.

In a diretl! $eated at$ode gro#nded'grid

ir#it it is neessar! to allow %ot$ t$e inp#t)F and t$e filament power to rea$ t$e

filament:at$ode wit$o#t interfering wit$ ea$ot$er- In t$e ir#it s$own at rig$t t$e two 4-41

#f apaitors permit t$e inp#t )F from t$einp#t mat$ing ir#it to rea$ t$e filament0

w$ile pre.enting t$e m#$ lower fre#en!

filament AC from flowing %ak t$ro#g$ t$einp#t ir#it- At t$e same time0 it is important

to keep t$e inp#t )F from flowing into t$e

filament power transformer- T$is isaomplis$ed wit$ a pair of $ea.! d#t! )F

$okes t$at are at#all! wo#nd on t$e same

ore- T$ese allow t$e low fre#en! $eater ACto pass t$ro#g$ w$ile %loking t$e m#$

$ig$er fre#en! )F- An! resid#al )F t$at

mig$t $a.e passed t$ro#g$ t$e )F $okes is

s$orted to gro#nd t$ro#g$ t$e two 4-4 #fapaitors- T$e filament transformer pro.ides

14 .olts AC at amperes to $eat t$e 813

filament-

Amplifier -l#te ee( %irc&it.

In an )F amplifier it is neessar! to

s#ppl! &C plate .oltage to t$e t#%e

a%o#t 444 .olts in t$is ase6 andat t$e same time e,trat t$e

amplified )F t$at appears at t$e

plate of t$e t#%e- In t$e ir#it at

rig$t0 t$e )'1> plate )F $okeallows t$e diret #rrent from t$e

plate s#ppl! B6 to pass t$ro#g$ it0

w$ile pre.enting t$e )F on t$eplate of t$e t#%e from flowing %ak

t$ro#g$ t$e plate s#ppl!- At t$e

same time0 t$e 44 pf plateo#pling apaitor at t$e top in t$e

s$emati6 permits t$e )F on t$e

plate to flow t$o#g$ to t$e o#tp#t

tank ir#it w$ile %loking t$e plate.oltage- T$e 44 pf apaitor at
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5/9

%ottom s$ort ir#its an! resid#al)F t$at mig$t $a.e gotten t$ro#g$

t$e plate $oke and pre.ents it from

rea$ing t$e plate s#ppl!- T$e smalloil in series wit$ t$e plate lead is a

parasiti s#ppressor0 w$i$ $elpspre.ent #nwanted osillations-

Amplifier -l#te T#n* %irc&it.

T$e plate tank ir#it is a pi'network

t$at mat$es t$e $ig$ impedane oft$e plate to t$e low impedane of t$e

antenna- At t$e same time t$e ir#it

filters o#t #ndesired $armonis fromt$e o#tp#t signal- T$e signal from t$e

plate enters t$ro#g$ t$e 44 pf plate

o#pling apaitor at t$e #pper left int$e s$emati- T$e two =4 pf

apaitors and t$e 4 pf .aria%le

apaitor0 in om%ination wit$ t$e

plate tank oil0 t#ne t$e plate toresonane- T$e two =4 pf apaitors

are plaed in parallel to prod#e an

84 pf apaitor- T$is is t$en plaed inseries wit$ t$e 4 pf .aria%le

apaitor- T$e res#lt is effeti.el! a

.aria%le apaitor wit$ a ma,im#mapaitane of a%o#t 2 pf- T$is

slows t$e plate t#ning rate and makes

t$e amplifier m#$ easier to t#ne-T$e %and swit$ .aries t$e

ind#tane of t$e tank oil0 and t$e

144 pf load apaitor ad;#sts t$e

network for t$e %est impedanemat$- T$e - m< )F $oke

performs two important f#ntions7 If

t$e plate o#pling apaitor s$o#ldfail and s$ort0 t$e )F $oke will

s$ort ir#it t$e plate s#ppl!0

$opef#ll! %lowing t$e f#se- T$is willpre.ent t$e plate .oltage from

appearing on t$e antenna0 a .er!

dangero#s sit#ation- T$e $oke also

pre.ents an! &C .oltage fromappearing aross t$e load apaitor0
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6/9

lowering t$e .oltage it is re#ired to$andle-

Amplifier !ri( 4etering

%irc&its.Metering t$e &C grid

#rrents of an )Famplifier is an important

met$od of monitoring

amplifier operation- In t$is

amplifier0 t$e ontrol gridand sreen grid are

onneted in parallel for

)F0 effeti.el! reating a9s#per9 ontrol grid- So

alled 9triode

onnetion9-6 T$o#g$ t$e!are in parallel for )F0 t$e

&C #rrent of ea$ is

meas#red separatel!- T$e

sreen grid and ontrolgrid metering ir#its are

idential and for larit!

onl! t$e sreen gridmetering ir#it is s$own

$ere- *a$ meter is

s$#nted wit$ a 144 o$mresistor- T$is permits t$e

amplifier to operate

wit$o#t t$e meter panelonneted- T$e 4-1 #f

apaitor gro#nds t$e grid

for )F rig$t at t$e t#%e

soket0 and t$e - m< )F$oke and 4-441 #f

apaitor make s#re t$at

no resid#al )F finds itwa! to t$e meter-


7/9

Amplifier -l#te 4etering %irc&it.

Metering t$e plate #rrent of an )F amplifier is e.en more

important t$an metering t$e grid #rrent- In t$is amplifier0

t$e plate #rrent meter is plaed in t$e negati.e lead of t$eplate s#ppl!- T$is keeps t$e meter near gro#nd potential and

keeps $ig$ .oltages off of t$e meter- T$e 144 o$m resistorgro#nds t$e negati.e lead of t$e plate s#ppl! B'6 if t$e

meter is disonneted0 w$i$ is a safet! feat#re0 %#t t$eamplifier annot %e operated wit$o#t t$e plate meter

onneted0 as t$e resistor alone annot $andle t$e neessar!

#rrent and wo#ld %#rn o#t- It is also important for t$e gridret#rn to %e onneted to t$e amplifier $assis gro#nd and

not t$e B' lead0 as onneting t$e grid ret#rn to B' wo#ld

a#se t$e plate meter to indiate %ot$ plate and grid #rrent-

Amplifier Tr#nsmit6ecei7e ),itching

%irc&it.

W$en an )F amplifier is #sed wit$ a

transei.er0 it is neessar! to %!pass t$e

amplifier d#ring reei.e periods- In t$is

amplifier setions 9A9 and 9&9 of rela!D1 $andle t$e transmit:reei.e

swit$ing- Setion 9B9 is #sed for %ias

swit$ing-6 W$en t$e oil of D1 is notati.ated amplifier 9"ff9 or in

9Stand%!96 t$e normall! losed EC6

ontats of rela! setions 9A9 and 9&9onnet t$e amplifier inp#t ;ak diretl!

to t$e o#tp#t ;ak0 %!passing t$e

amplifier- W$en t$e rela! oil isati.ated amplifier in 9"perate96 t$e

inp#t ;ak is onneted to t$e inp#t of t$e

amplifier 9I9 .ia t$e normall! open E"6

ontat of setion 9A9 and t$e o#tp#t;ak is onneted to t$e o#tp#t of t$e

amplifier 9"9 .ia t$e normall! open

ontat of setion 9&9-


8/9

Amplifier 4o(e ),itch #n(

6el#y Acti7#tion %irc&it .

"ne side of t$e 11> .olt AC

line from power ;ak P1 ont$e rear of t$e amplifier6 is

ro#ted t$ro#g$ a Amp f#seto t$e rotors of setions 9A9

and 9B9 of mode swit$ S1-T$e ot$er side of t$e AC line

is ro#ted to one side of t$e

filament transformer andrela! D1- W$en mode swit$

S1 is in t$e 9"ff9 position0 t$e

AC is disonneted from t$efilament transformer and

rela! and t$e amplifier is

t#rned off- W$en S1 is set tot$e 9Stand%!9 position0 t$e

filament transformer and

green stand%! lig$t are t#rned

on and t$e amplifier is in9Stand%!9 mode- W$en t$e

mode swit$ is plaed in t$e

9"perate9 position0 rela! D1is also ati.ated0 plaing t$e

amplifier in 9"perate9 mode-

T$e amplifier an also %e

remotel! swit$ed from9Stand%!9 to 9"perate9 %!

s$orting pins 9C9 and 9&9 of

%ias and ontrol ;ak P3 ont$e %ak of t$e amplifier-

Amplifier +i#s %irc&it.

T$e amplifier %ias ir#it

applies ad;#sta%le %ias to

t$e 813ontrol and sreengrids0 w$i$ are r#n in

parallel- So alled 9triode

onnetion9-6 In9Stand%!9 mode t$e oil

of rela! D1 is not

ati.ated0 and one end of

t$e 4k potentiometer isleft #nonneted- T$is
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9/9

applies t$e f#ll o#tp#t oft$e %ias s#ppl! to t$e 813

grids to #t t$e t#%e off-

ring 9"perate9 mode0t$e oil of rela! D1 is

ati.ated0 and t$e end oft$e 4k potentiometer is

gro#nded0 red#ing t$e%ias to t$e .al#e seleted

%! t$e %ias ad;#st

potentiometer- In at#aloperation t$e t#%e is

operated wit$ ero %ias so

t$e wiper is set at t$e%ottom end of t$e

potentiometer-
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the aa8v wingfoot 813 amplifier

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