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4. ADJUSTMENTS
NEUTRAL
POTENTIAL ADJUSTMENT
1. Push the Speaker selector push-button A with the Power switch "ON".
2. Connect
the DC voltmeter
to speaker terminal A and check the meter oscillation is kept within from +20mV
to —20mV.
See figure 8.
screwdriver.
Note:
Be careful not to short-circuit the pattern with screwdriver during adjustment.
DC Voltmeter
Speaker Terminal
Figure 8.
IDLE POWER
ADJUSTMENT
1. Connect the DC voltmeter to the both terminals of R645 (Rch.) and R646 (Lch.) and check the meter oscillation
is kept within from 1mV to 2mV. See figure 9.
|
2. When
the voltage deviates from the above scope, adjust the Semi-fixed
resistors R653 (Rch.) and
R654
ae
with screwdriver.
Note:
The adjustment should be made one minute later after turning the power on.
Be careful not to short-circuit the pattern with screwdriver during adjustment.
CHECKING
PROCEDUSE
OF MAIN P.C. BOARD
BACK
1. After removing the Bottom
plate, unsolder the 12 (3 x 4) pins of 4 power transistors (Q617, 618 ... 2S5D718,
0619, 620 ... 2SB688)
from the Main P.C. Board and solder 4 pcs of 100 ohm %W resistor (22563101) between
emitter and base on the pattern at four points. See figure 9.
Caution:
The pins of the four transistors unsoldered should
be fell toward radiator Sa away from the P.C.
board.
Never apply power before attaching the resistors.
2. Apply power and keep the Power switch all the way in ON position.
To check the neutral potential, make sure that the voltage is kept within from +20mV
to —20mV,
connecting
the speaker terminal to DC voltmeter.
DC Voltmeter
|
Speaker Terminal
Figure
10.
Signal Generator
Ss
AC Voltmeter
WIRING REARRANGEMENT
Caution:
Failure of this rearrangement may results in bad distortion in high-pass.
After fixing the P.C. board and soldering the power transistors, rearrange the wiring as figure 12.
ay
~ (bring to the left as ae
2 Core Shield
Mini-connector 10P Lead
(bring to the right as possible)
(place close to speaker terminal
Earth ead (brown)
and bottom plate as possible)
(place close to speaker terminal
as possible)
Figure
12. Bottom View
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