6-4.
TROUBLE-SHOOTING
CHART
SYMPTOM
CAUSE
REMEDY
Fuse
blows with V6 out
of
socket.
Short
in
T1
Replace
Fuse
blows only with
V6
in
socket.
Defective
V6,
short
C7
Replace
Filament not lit.
Open heater
in tube
Open
green lead for T1
or leads
to filaments.
8.3V
winding of
T1
open
Replace
tube
Replace
T1
POWER
bulb doesn't light
Defective
R18,
12
Replace
MX
stereo
bulb
doesn't
light
when
stereo program is
in
progress
Defective R10,T2,T3,I1,C6,
CR1, CR2
Replace
MX
stereo bulb lights
only
with VI out of
socket
Misaligned
T2
and T3
Realign
DC
voltage at
V6
cathode
(pin
7)
is incorrect as speci-
fied below:
a)
No
voltage
Defective V6
C7
shorted
internally or
externally
Connection
to center
top
of h.v.
secondary winding of
T1 open
Replace
Repair
or
replace
Repair or
replace
b)
High
voltage Lead
from
C7C, R19,
or R20
open Repair or
Replace
c)
Low voltage T4
shorted
to ground
C7A
open or shorted
V6
defective
Replace
Replace
Replace
Excess hum C7
open
Replace
Sustained
microphonics
Vl defective
Replace
Distorted Stereo
T2,T3,T4 out of
alignment
Realign
Lack of
separation
V2,R31,R33,R34,R35,CR1,CR2,
CR3,CR4,
CR5,CR6
Replace
High-pitched
whistle
on certain
FM
stereo
stations
67kc
(SCA sub-carrier)
trap T5
misaligned or
defective
Realign by
adjusting
coil slug for
inaudi-
bility
of
whistle. If
defective, replace.
6-5.
SPECIAL
OPERATING
NOTES
The MX-99,
as
supplied,
incorporates
a
capacitor,
C25,
having a
value of .001
mfd and
associated
with
input stage
VIA,
which is
designed
to
provide
optimum
compensation for
the
high frequency
roll-off (at
53kc)
of
all EICO
tuners (HFT-90,
92 and ST-96).
When
using
the MX-99
with one
of
these EICO
tuners
that is
properly
aligned
and
operating
normally,
the optimum
setting
of the MX-99
SEPARATION
control
will usually
fall
somewhere
between4and 8
on the
dial,*
andat this
setting
separation
will
be
maximum across
the
audio
band.
There are
two
other cases
involving the use
of
the MX-99
with
other brands
of FM
tuners.
Provided that the
station is
employing the
modulation
percentage
practices recommended
by the
FCC,
i.e.,
45%
main carrier,
45%
sub-carrier,
10%
pilot carrier.
Check
with the
station
involved.
CASE
1
If you
are
using
the MX-99
with another brand of
FM
tuner,
and you
find that
maximum separation
is
obtained
with
the
SEPARATION
control set
somewhere
between
0
and
4,
you
can
usually maximize
high-
frequency
separation and
reduce distortion by
removing
capacitor
C25
from the
circuit.
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