Hitachi HA-7700 Serviceanleitung Seite 9

To adjust the Rch, connect the @ side to the R IN
terminal, and the © side to the G6 terminal. Then
perform the adjustment using R703L or R703R res-
pectively for a zero reading (within + 0.5mV) with the
3mV range. (Fig. 9)
ene"
Fig. 9
® Adjusting the output DC
Be sure to perform this adjustment after the input DC
adjustment is completed.
Insert the shorting pin in the input, set the DIRECT
COUPLING/CONDENSER COUPLING switch to CON-
DENSER COUPLING, turn the speaker selector switch
ON, and perform the adjustment with no load.
Perform adjustment using R709L or R709R after con-
necting the DC voltmeter to the @ and © sides of the
speaker A terminals of Lch or Rch for a zero reading
(within +5mV) with the 100mV range. (Fig. 9)
HITACHI HA-7700
@ Adjusting the equalizer output DC
Insert a shorting pin into the input terminal of PHONO-1
and set the function switch to PHONO-1, and PHONO
selector to 47kohms. Next, connect a 680 ohms
resistor to the positive @ terminal of the DC voltmeter
and connect it to the test point TP.L or TP.R. Connect
the negative © terminal to G21. Adjust R426L or
R426R so that the voltmeter reading becomes 0 in the
1V range and within +100mV in the lower range. Be
sure to connect the resistor to the voltmeter because
oscillations may occur if adjusted without the resistor.
Equalizer P.W.B.
680 ohms
Detach
AC voltmeter ae
Audio oscillator Oscilloscope
Fig, 11
2. Operation check of the speaker protection circuit
Make sure that the relay operates (a click sound isheard)
approx. 4-7 seconds after the power switch is tuned on
with the speaker terminals unloaded (speaker dis-
connect).
Next, when a resistor of approx. 10 kohms and2 dry
cells (1.5V) are connected in series to the earth pattern
on the audio printed wiring board and the VQ teminal,
the relay turns off within 1 sec. When the dry cdIs are
taken away, the relay operates again. Next, chane the
polarities of the dry cell and carry out the ibove-
mentioned operation to check the operation of therelay.