Philco 16 - Philco 16 Series Frequency Drift and Tuning Issues; Philco 16 Series Frequency Drift Solutions; Philco 16 Series Waveband and Tuning Problems

Sec. 1
"Case Histories•• of Receiver Troubles and their Remedies
PHILCO 1', 1'B, 1'X, 1'RX-(CodH 1%1, 12Z)-(Co11t',f)
Fadinc on _______ 1)
variable tuning condenser imperfectly
crounded to chassis. Bond condenser
frame to chassis with heavy flexible pig-
tails which will not interfere with "float-
ing" mounting
•hort-waye
bands
Oscillator drift
2) clean the rotor-shaft contacts
S) .tighten all screws on gang condenser,
and between gang condenser and chassis
4) waveband switch not grounded perfect-
ly. Ground frame of waveband switch
to chassis with pigtails
5) replace fibre insulator on high-frequency
compensating condenser with new and
thicker type
Frequency _________ l)
in order to alleviate frequency drift it
is recommended that the first and second
i-f transformers be replaced with part
No. 32-1186, using compensating con-
denser assemblies (Part No. 91-6090),
with shunt condensers, (Part No.
30-1086) connected across both the pri-
mary and secondary sections. The third
i-f transformer should be replaced with
Part No. 31-1866 using compensating
condenser assembly (Part No. 31-6003),
no shunt condensers being used
drift
(due to i-f
drift)
Frequency _______ l)
drift
( due to dial-
creepinl')
Volume un- ______ l)
controlled
Code inter- ------1)
ference
Whi:stlinc or ______ 1)
1quealinc
(intermit-
replace tension spring on back of gang
condenser -using improved Part No.
77760
if at zero volume control setting and
with the QAVC switch in the S position
the volume does not reach minimum or
zero, replace the 0.02-mfd. condenser in
the 78 QAVC control-grid circuit with
a 0.01-mfd. condenser
readjust wave trap for minimum inter-
ference. In extreme cases, reduce the
i-f to a lower value-say 440 kc. The
high and low frequency compensating
condensers of the oscillator circuit
:should be readjusted in order to repro-
duce the correct i-f
if accompanied by .image signal check
0.05-mfd.
condenser No. 15 for "open."
Connected from first detector grid re-
turn to ground
tently or
:steady)
2) check 0.05-mfd. condenser No. 48 from
second i-f plate supply filter resistor to
cround
3) solder pigtails from all r-f, i-f and oscil-
lator transformer shield cans to ground
replace loose tuning meter bracket
4)
Hum ---· ----------1)
(in early
replace the a-c switch jumper from
switch through terminal lug mounted on
condenser at back of set with shielded
wire (with the shield grounded)
:series)
Hum ----·--·--------1) check for "open" 0.3-mfd. condenser No.
16 connected across filter choke
Tone impron-----1) connect a 0.006-mfd_ 400-volt tubular
rnent condenser from the 77 tube plate to the
( early models) tone-control connection
Two resonance --1) replace shadowgraph with improved part
peaks indicat- number 45-2021
ed on shadow-
graph,
Widening of
shadow upon
r•sonance
(Cont'd)
PHILCO 1', 1'B, 1,x, 1,RX-(Codea 121, 122)-(Cont'tl)
Choked -----1) open-circuited 2-mfd. by-pass condenser
B in condenser block
2) open-circuited 0.5-mfd. first audio plate
by-pass condenser
Noisy reception 1) defective shadowgraph bracket. Replace
Motorboating ----1) check for "open" section in condenser
sound block No. 62 (capacitiH 2-2-mfd., 2-0.06-
(steady or in- mfd., 1-1-mfd.)
termittent)
PHILCO 16, 16-X, 16-RX (Code 123)
See also the Case Histories listed for Philco 1~ (Codes 121
and 122) receivers
Inoperative on -.1) high-resistance contacts in waveband
S-W band switch. Replace wtih new switch
Intermittent ______ 1) intermittent connection between coil
reception lead and hook-up wire in third i-f trans-
former
PHILCO 1', 16B, 16X (Codes 125, 126)
Inoperative ______ l) replace 0.05-mfd. condenser No. !% con-
n•cted from filter resistor of r-f ampli-
fier plate supply to ground (open
shadow on tuning meter)
2) replace twin 0.05-mfd. condensers No. 15
connected from each side of shado-.r-
graph to ground (open shadow on tun-
ing meter)
3) check 1-mfd. condenser No- 79 connect-
ed from screen grid of 77 first audio
tube to ground •
4) check 0.05-mfd. condenser No. SI con-
nected from filter resistor of second i-f
plate supply to ground
5) cheek 0.25-mfd. condenser No. It con-
nected from filter resistor of first audio
plate supply to ground
Inoperative, ______ l)
check contacts on band switch. These
contacts may shift or drop out complete-
ly. (This condition may be indicated by
Weak reception
short wave reception coming in on the
broadcast band setting, and by improper
tracking of the oscillator)
Weak nception _}) check 0.003-mfd. condenser No. 11 con-
nected from ave load resistor of first r-f
tube to ground. Breakdown indicated by
inability to peak on broadcast band pad-
der
2) check for "gassy" 5Z3 tube
Weak reception._ 1)
(intermit-
tently)
Weak reception. 1 )
No plate volt-
age on second
i-f tube,
Wide shadow-
graph indica-
tion
Intermittent _l)
reception,
check compensating condensers No . .JI
(first i-f primary), No. 49 (second i-f
primary), No. 55 (third i-f primary).
Tapping the i-f transformer cans will
usually indicate intermittent condenser.
Replace faulty one
open-circuited 500-ohm wire-wound pig-
tail type second i-f tube cathode bias
rui:stor
open-circuitin~ 0-06-mfd. cond•n:ser con·
nected between the junction of the two
diode load resisto1·s and the bottom lur
of the volume control ·
Very weak sig-
nals (shadow-
graph
operates)
2) open-circuiting by-pass condenser. Trou-
ble in lead contacts
3) open-circuiting 250-ohm resistor a11em-
bly blocks in i-f plate circuit
(Cont'd over)
155