Philco 57-122 Manual

PHILCO
RADIO MODELS 57.122 AND
Circuit Description
'I'hc
Philco
Nlorlcls
1'r7-122
antl
ir7.I-122
itrc
ir-tttbc,
t:rblc-rttorlcls
strlrcrhctcrotlytrc
t'atlit>s,
pt'ovitling rcccl)-
tiorr in thc st:rnilartl
l>ro:ttlt::tst
lr:trr<1.
-l'hc
high-inrPcrlance
l<><_r1t
acri:rl
nor.rrrally-
1tr'ovirk's
:rrlccltratc
"signai
ltick-tr1t.
An
cxtclrral acrial ntay
bt'
conricctcd,
'if
clciirecl,'lly tletaching
thc aclial
lcatl
(shown
in
figurc 6) fro-ri thc-chassis,
and conncctine
tirc
leacl
to
art
cxtcrnal acrial lcatl-in.
I)o
not
tlsc
a
grotttrtl.
'I'ltc loop is
cotrpletl
to tltc
7A8 coll\Icrtcl' tttbc.
Vari:rltlc-coirrlenscr
funing is
crrrployccl,
thc oscillator
l-ot()r-scction
platcs
bcing shapcd
t<l
obt:titr
tracking,
thrrs elirninaiing
the
ncccssity
for a
scrics patltling
t:onrlctrscr.
T'hc 7A8
is
trausfiorttrer
cotrplctl
to thc l4A7 i-f
:rrnplificr, n'hich
is
also
tratrsfot'nrct'
t'rtttplecl
to
thc
rlio?lcs
of thc
l4R6
second
dctcctor
-
first
arrdio-frc-
(tuency
arnplificr. A-v-c voltage is applictl to
thc
.irntt.rl
gricls
o[ both thc
i-[
antl cotrvcl'tcr
tttbes.
-I'hc tri<ltlc
scction
oI thc l4I]6 is thc
first
autlitr
sta{rc,
and is
resistatrce
cotrplctl
to thc
50A5
otltPtlt
trrbc.
Thc
otrtpttt ttttrc is trartsiorlllcl'
clottplctl t<l
:t
l)crrnanent-nlaglrct
<lyrrarnic spcakcr.
l)-r:
<rpcr:rting
voltagcs arc
olltaitrctl [t'ottt
a
!ll>Z!>()'l
lr:rl[-u'avc
rcctificr, thc otrtptrt
of u'hich is filtcrccl lly
1r
tlu'cc-scction rcsistor-contlenscr
filtcr.
(londenscr C304
in
Section 3 is a sltcciirl cotttlctrsct',
irrdtrctively
r,r'otttrct
to form
a
scries-trrned
circttit,
rcsott-
irnt at thc
interrttecliatc freqtrency.
Tilis
spccial
corr-
rlenser
oflers less
intpcdance
at this
frcqtrcncy
than
a
convcntional contletiscr, thtrs
llclrrrittinu higher
i-l'
g-ain,
rt'ith no tentlent'y tor.t'artl
inst:rllility.
Philco TROUBLE'SHOOTING Procedure
In this nlatrual, thc
schetnatic
diagratlr is
tlivitlcd
int<r
lour
scctior-rs,
with a
chassis
layotit
for
citclt
section,
showipg component ancl
test_.points
for
each section.
The teit poihts are also indilatecl
on the
schernatic
rliasram
i" the
corresponding
section.
A
sirnplifiecl
troilble-shooring procedtrre is
given
in
a
chart
for
each
secrion.
f'he
nisd step
in caclichart
is a rnastcr c5eck,
irrdicating whethcr
tiotrble cxists
in that section. Fail-
rrrc
to oiitairr tlrc "NORNIAL INDI(IATION" in
a
q.ivcn
setul) inrli<':rtcs
trottblc, u'hich shottlcl
llc
locatc<l
'bv yoltagc,
rcsist:rncc,
or
capacitancc' chccks
o[
parts
iritli<-ateti'
in rhc
stcl), antl
-t'clnctlic<l
lrt'fot'c
tcrstins
lrr
rthcr.
MODEL 57-122
(Wolnut)
MODEL 57.1-122
(lvorY)
SPECIFICATIONS
(]ATIIN
ET
I'lastic
Cabinet; walnut
and
ivory.
CIRCUIT
.
5-tube
suPerheterodYne
FREQUENCY
RANGE
540-1620 kc'
OPERATING VOLTAGIT
f05-f
20
volts, a'e'
or
d'c'
I'OWER
CONSUMPTIONS0 watts
AUDIOOUTPUT
.l
watt
Built-in loop;
eonnection
for external aerial
160 kc.
7A8.
l.lA7, l,ltl6,
50A5.
35Z5GT
TP
I
60864
AERIAL
INTERMEDIATE
F
RE(lL/ENCY
I'HILCO TUI}ES
(5)
l.
Preliminary
Checks
'I'o
avoitl
possible
clanrage
to
thc t'adio, the follow-
irrg
prcliminhry
checks
should be made before
turning
on the
power:
Carefully inspect
bot\ top and bottom of
chassts'
Nlake s.tre
that all
tubes
are
secure
in
the
ProPer
sockets (sec
figurc 6), and look
for bad
connections,
burnccliesirtSrs,or bther obvious sources
of trouble.
l\Ieasure
the
resistance
between
B
*
and
B-
(test
points
C
and
B
in
figure
I
),
using
the
ohmmeter
irolarity giving the
h"ighest'resistince-
reading;
if
itr" r"uhifrg is
i-orver
thai
50,000
ohms,check
Cl0lA,
(llOlR,
"ia
Cl0lC;,
for
leakage
or
shorts. This
rcsistancc
valtte,
rvhich
is
much-lower than normal,
rlncs
not
represent
a
qtrality check
of
these con-
rlcnsers:
it
is'the
lorvest
valttc'which
rvill permit the
rectifier to oPerate safely
rvhile the voltCge tests
of
Section
I
(porver srrpply) are performed.
Cana<l:r,
l1)4s
2.
I'h
i l<
o
(ior'lrot
it
t
iot
t
of