Philips N4307 - Level Indicator Adjustment; Cleaning; D.C. Voltages

level indicator may be adjusted with R446 so that it registers on the division
between
the
red
and
black
sectors
of
the
scale.
Remove
the
input
signal
and
switch
to
“‘Record”’;
the
meter
pointer
should
be
deflected
up
to
a
maximum
of 1mm., due to bias current.
Correction Coil L2 (adjusted only on replacement): Depress the ‘‘Record”’
key
only
and
apply
a
1
kHz
signal
to
pin
3,
Sktz,
so
that
a
voltage
of
0-775
mV,
measured with an A.C. millivoltmeter, is present at MPx, with the track
selector switch S2 set to position “1-4”. Change the input signal frequency to
14kHz. The voltage at MP1 should now read 3-5mV; adjust correction coil
L2 for this reading, then seal it with locking paint.
Cleaning: The magnetic heads, tape guides and capstan should be cleaned
at regular intervals if optimum performance is to be maintained. Remove
cover for access to these parts, which can be cleaned with a soft cloth wrapped
around a wooden stick and moistened with methylated spirits or industrial
alcohol. Metal objects should not be allowed to come into contact with the
magnetic head faces.
After
approximately
500
hours
of
service,
it
is
advisable
to
clean
the
follow-
ing
parts with
methylated
spirits
or
industrial
alcohol:
Magnetic head faces; Tape guides; Capstan and pressure roller; Drive
belts; Grooves in flywheel and pulleys; All friction driven surfaces; Brake
shoes and braking surfaces of turntables. Clean the inside of both turntables
with a soft dry brush and if necessary clean or replace pressure felt.
D.C. Voltages—Switch to “ Record”.
Stage | Collector | Base | Emitter
Tr 1°35 0°62 —
T2 1°38 0-6 ——
13 1°82 0°62 0°16
T4 5°3 1°18 0°65
Ts 7-6 0:8 0°65
T6 13'0 1°S7 I*44
T7 — 130 13'I
TS 24'S 13°3 13'2
Tro 10°8 orl 0°78
Switch to “ Playback”’.
Stage | Collector | Base | Emitter
Tr 1°36 0°62 —
T2 1°33 0°59 —
T3 I'9 0°68 018
T'4 5°6 1°22 O'7
Ts 8-6 1'99 P37
T6 13°25 1'6 I°47
a7 — 13°25] 13°4
T8 2.5 13°6 13°5
Ti10
—
—_
=