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4 Bias
current
1. Adjust bias current when
heads or other parts are
replaced.
2. Use the highclass V.T.V.M.
for high frequency re-
sponse.
3. After the bias current
adjustment, check the fre-
quency response at 10kHz
signals.
(Main amp
C. board)
3. Adjust semi-fixed resistors R604,704
(chrome) 605,705(normal) so that the
10kHz frequency response does be-
chrome
quency response.
Level over at 10kHz compared with
1kHz — bias current less
Level less at 10kHz compared with
1kHz — bias current over
level control so that the VU meters
adjusting steps(1) through
indicate zero VU.
(4)
according to type of tape
used.
R324 ,424
(REC
GAIN)
R338,438
(DC
BIAS)
R325,425
(CONT
GAIN)
R312,412
(PB GAIN)
2. Set the deck in the record mode.
3. Input 1kHz —10dBs signals from LINE
IN jacks adjust the recording volume
controls so that the voltage across
LINE OUT is —5dBs.
4. Turn R325 and R425 (CONT GAIN)
and R338 and R438 (DC BIAS) in the
direction opposite to the marking.
5. Adjust R324 and R424 so that level
does not change when ANRS is turned
on and off, and turn on ANRS.
6. Input 1kHz, —50dBs signals from
LINE IN.
Adjust R338 and R438 so that voltage
across LINE OUT is —-39.5dBs.
7. Input 5kHz —30dBs signals from
LINE IN.
Adjust R325 and R425 so that voltage
across LINE OUT is —21.5dBs.
8. Repeat steps(5) through (7).
9. Turn ANRS switch is "Super" position
when input 10kHz -10dBs signals from
LINE IN.
Check output levels are -11dBs +2dB.
10. Connect receptable of bias oscillator
disconnected in step (1).
11. Play reference tape VTT-664 and adjust
R312 and R412 so that level does not
change when ANRS is turned on and off.
CD-1770/A/B/C/E
No. 4144
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