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HITACHI
HMA-8500MKT
ADJUSTMENTS
1.
2.
Idling current
Connect the © side of a voltmeter to the test point
shown in Fig. 3 via a 1 kohm resistance. With R757L,
R and R758, R at their leftmost positions, switch on
the power and when at least 8 minutes have elapsed
and
R757L,
R and
R758L,
R have
been
shifted
separately to the semi-fixed center position, rotate
semi-fixed resistor (1) at the side where the voltmeter
pointer deflects in a clockwise direction (with the
other semi-fixed resistor (2) at its leftmost position),
and adjust the deflection of the DC voltmeter to 30
mV. Now rotate the other semi-fixed resistor (2) in
the clockwise direction and adjust the voltmeter to 32
mV.
Rotate the semi-fixed
resistor (1), which was
rotated first, in the clockwise direction and adjust to
33 mV. The method of adjustment is the same for the
left and right channels.
Adjusting the meter
(1) Zero adjustment of the meter
(2)
If the meter point has shifted off the zero point even
though
no signal or noise is entering the input,
remove
the escutcheon
and adjust the zero ad-
justing lever so that the pointer of the meter comes
to the ''0" position of the scale plate (Fig. 4). After
adjustment, adhere a piece of tape over the adjust-
ment hole.
Adjusting the meter sensitivity
Adjust sensitivity of the meter after zero adjustment
is completed. With no load applied to the speaker
terminals, connect the audio oscillator to the CON-
DENCER COUPLING INPUT to feed in a signal of 1
kHz. Set the BTL switch to OFF and Meter range
selector to 8 ohms position.
In this case, adjust the output of the audio oscillator
fora speaker terminal output voltage of 8.98 Vrms.
Then, adjust R508L and R508R so that the pointer
of meter reads 10 W under these conditions. (Fig.
5)
When
performing this adjustment,
adhere a piece
of insulating tape to the screwdriver so that it does
not touch the chassis. If it does touch the chassis,
the fuse may blow and damage may be caused.
O
Screwdriver
Schraubenzicher
:
fs
ane
Fig. 4
Tournevis
Abb. 4
Heat
sink
fin
[
/
Kuhtkorperrippe
—
Aifette
de
|
7
dissipateeur
thermique
R506R
RS508L
=
Fig. 5
Abb. 5
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