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BASS CONTROL 1, BASS CONTROL 2 (CONCENTRIC):
The plus sign on the right side of the dial indicates that
clockwise rotation from the mid- point (0) of either control
increases (boosts) _
bas~ response; the minus sign on the
left
side indicates that counter- clockwise rotation from the
mid- point decreases (cuts) bass response. There is no in-
teraction with the
TREBLE
control.
Start all adjustments
with this control set at the mid-
point (0), which is called
the "flat" position since bass response
is neither cut nor
boosted at this position.
maintenance
TREBLE CONTROL
1, TREBLE CONTROL 2
(CONCEN-
TRIC): The plus sign on the right side of the
dial indicates
that clockwise rotation from the mid-
point (0) of either
control increases (boosts) treble response; the
minus sign
indicates that counter-
clockwise rotation from the mid-
point decreases (cuts) treble response. There is no inter-
action with the
BASS control.
Start all
adjustments with
this control set at the mid-
point (0), whi ch
is called the
flat" position since treble response is neither cut nor
boosted at this position.
GENERAL
Your amplifiershou Id require I ittle
service except for nor-
mal tube replacement. We recommend no substitutions for
the tube types used in this amplifier except as stated. All
the tube types used are distributed national Iy, but
replace-
ments can be obtained directly from EICO if desired.
To facil
itateservicing, remedial and trouble-
shooting pro-
cedures have been provided in the TROUBLE-
SHOOTING
CHART that follows. A VOLTAGE AND
RESISTANCE
CHART is also provided
as an aid in
locating defective
components. DC operating voltages are given both at no
signal and signal developing 14 watts
output, as well as
the corresponding 1 kc signal voltages.
TROUBLE-
SHOOTING PROCEDURES
Connect the leads from the stereo cartridge and from the
two speakers to the amplifier.
These connections are made
as described in the section "
Electrical Connections " . Set
the Input Selector control at PHONOand the Function Se-
lector at STEREO. Playa known high quality stereo
record-
ing on the phonograph. If there is no output to the speaker
of if the output is low or audibly distorted
, procede to the
checks for those symptoms. If there is
excessive hum in
. the output
, disconnect the phono input cable
from the
ampl ifier and short the phono input
jack to chassis. If the
hum disappears, the trouble is not in the amplif.er but in
the phonograph or in the connection to the amplifier.
each case, check for the trouble in the amplifier which
seems defective. If both
amplifiers are defective, check
the power supply.
The cause of phonograph hum may be a metal pick-up arm
not grounded to the cable shield (try a good single ground
connection to the cable shield from turntable frame, pick-
up arm, and cartridge case), direct
hum pick-up by the
magnetic cartridge from the record player motor(tryusing
a rubber mat on the turntable to increase the separation of
the pick-up from the motor), or pick-up from a power
transformer or other magnetic
field in the vicinity
(try
moving phonograph away from suspected source). Check
also that the phono input cable shielding is
grounded to
the ampl !fier chassis at one point only, through
the skirt
of the input connector where it
plugs into the ampl ifier.
Finally, try a good building ground such as a connection
from a cold water pipe terminated under speaker terminal
G" on the amplifier
Do not connect such a ground wire
to other
components in the system
If possible, let each
channel be connected to the amplifier
using a separate
shielded cable to the ampl ifier input. It is
also desirable
that the ground leads on both cables not be
connected to-
gether at any point
- not even at the
cartridge.
How-
ever, with some
cartridges, it will not be possible to do
this. In this case, just disregard
this last instruction.
Excessive hum on other inputs may be checked in a similar
manner. Disconnect the input cable in question and short
the particular input jack to the chassis. If the hum dis-
appears, the trouble is external to the amp!
ifier.
Note
that on all
inputs, the braid of
th;;; input cable shou Id con-
nect to the ampl ifier only through the skirt of the input
connector. The cause and
remedies for the following
symptoms are then based on the
assumption that checks
made in the manner described above have eliminated the
possibilityof the trouble being external to the amplifier.
If the trouble is no output or low output
, check AC signal
voltages and DC operating voltages starting at the input
and work step_
by-
step toward the output in each ampl i-
fier. Set the
VOLUME control to
maximum (10), the
FOCUS, BASS and
TREBLE controls
to their mid- points
(0), the
INPUT SELECTOR to PHONO and the FUNC-
TION SELECTOR to STEREO
. Use a 1000cycle sine-
wave signal
, such as supplied
by the EICO 377 Sine &
Square Wave Audio Generator
In addition, use a pre-
cision 100: 1 attenuator to permit obtaining a
level of
0035 volt fed into MAG. PHONO
from an audio gen-
erator output of 0. 35 volts, which can easily be measured
onthelowestACvolts range ofyourVTVM
(also improves
signal to
hum from generator). Use a high
input imped-
ance VTVM for all AC signal voltage
measurements; a
VTVM or 20,
OOOQ/v
YOM
for DC volts measurements.
. If the trouble
is an excessively distorted output, try tube
replacement, signal tracing, or procede directly to vol-
tage and resistance measurements.
When the defective stage is local ized, procede
to a resist-
ance and voltage check of the stage, using the data in the
VOLTAGE and
RESISTANCE chart. Disconnect theampli-
fier from the power line and discharge capacitors prior to
making any resistance check and prior to removing any or
all of theEL84output tubes.
Do not turn the amplifier on
with any of the output tubes
remove
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Troubleshooting
