JVC KD-A11 - Page 12

KD-A11A/B/C/E/J/U
No. 4192
sensitivity
Checking
record/
response
Checking
record/
playback
signal dis-
tortion
Set the cassette deck to its recording
mode.
Apply a 1 kHz, approx. —10 dBs signal
to the DIN IN terminals.
Adjust the recording level controls un-
til the signal is available at — 7 dBs at
the DIN OUT terminals.
Adjust VR 151 and VR 251 until the
VU meters deflect to 0.
Record 1 kHz, 100 Hz and 12.5 kHz
signals at an input level of O VU to —20aB.
Play back the tape.
Check to see that the 100 Hz and 12.5 kHz
signal output deviations fall within the
standard range, using the 1 kHz signal out-
put as a reference. (It is basically desirable
that the 1 kHz, 100 Hz and 12.5 kHz signal
outputs are the same.
Record 1kHz, 100Hz and 12.5kHz signals
at an input level of OVU to —20dB. Play
back the tape.
Adjust VR103 and VR203 (for a normal
tape), VR104 and VR204 (for CrO2 tape),
until the indicated deviation of the 12.5
kHz signal output from the 1kHz signal
output becomes 0.
Apply al kHz, approx. —10 dB signal
to the DIN IN terminals. Adjust the
recording level controls until the signal
is available at —2 dBs at the DIN OUT.
After checking to see if the VU meter
becomes to O, record the signal applied
to both left and right channels using a
normal tape.
Play back the recorded part.
Perform the recording signal adjust-
ment with VR181 and VR281 so that
the VU meter becomes to 0.
Record a1 kHz, 0 VU —7 dBs signal
to DIN IN terminals and perform
recording with the VU meter becomes
0 VU.
Play back the recorded part. Check the
output with a distortion meter to see
if the value conforms to the standard
value.
Perform the adjustment when the
parts are replaced.
For nor- Reference | This checking should be performed for
mal tape: | frequency;
VR103, 1 kHz
203
For CrO2 | 043 dB
tape: at 100 Hz
VR104, 0+3 dB
204 at 12.5
Response (dB)
Normal tape;
less than 2%
normal, chrome and metal tapes and
for both right and left channels.
Fe-Cr and METAL tapes use only to
check.
Bias current adjustment for a cas-
sette deck should generally be per-
formed referring to the record/
playback frequency response.
This is because the frequency
response of a cassette deck
depends more greatly upon the
bias current than does that of an
open reel deck.
The current measuring method
described below is an alternative
one.
If the bias current is not properly
adjusted the record and playback
characteristics become as shown
below.
Increase in high frequencies
(with a small bias currént)
Optimum level
Decrease in high frequencies
(with a larger bias current)
1kHz 12.5kHz
Frequency (Hz)
The level difference between left and
right channels for normal tape, chrome
tape and metal tape should be less
than 1dB (1 VU). Perform the adjust-
ment using a normal tape, level differ-
ence between recording and playback
for CrO2 and metal tapes should be
less than 1.5 dB, and that between left
and right channels should also be less
than 1 dB.
Be sure to perform this adjustment fol-
lowing bias current and recording level
adjustments.