Technics RS-646DS-D

Level meter
Equipment:
+ VTVM
* Oscilloscope
* AF oscillator
+ ATT
Overall distortion
Equipment:
* Distortion meter
* AF oscillator
* ATT
* Oscilloscope
* Test tape---C-RA
(reference blank tape)
MEASUREMENT & ADJUSTMENT
When standard recording level is supplied
1. Test equipment connection is shown in fig. 21.
Bw
AF Oscillator
LINE IN LINE OUT
ATT Record mode
Fig. 21
.
Set
the
bias
selector
to
“LOW”
and
the
EQ.
selector
to
"120uS".
.
Supply
1kHz
signal
(~24dB)
from
AF
oscillator,
through
ATT,
to
LINE IN (L-CH) jack.
. Adjust ATT until monitor level at LINE QUT (L-CH) jack becomes
0.42 V (—7 dB) and confirm that the level meter indicates 0 VU posi-
tion.
. If in the above condition, the level meter doesn’t indicate OVU posi-
tion, change the “Connection points” of the amplifier pattern, and make
the adjustment.
D
If
the
indication
of
the
left
channel
meter
is
below
—1.5dB,
short
circuit connection point © as shown in fig. 7.
@
If
the
indication
is
still
insufticient
by
shorting
connection
point
©,
short
circuit
connection
point
©
also
as
shown
in
fig.
7.
.
Adjust
VR11
so
that
the
right
meter
will
indicate
the
same
value
as
the left meter. (See fig. 28 on page 17).
REMARKS
* Record mode
. Test equipment connection is shown in fig, 22.
co
ATT 6002 Record
mode
LINE OUT
law 3
oscillat
AF
oscillator
Test
tape
R/P head
Playback mode Disto Higa?
meter
Fig. 22
Supply 1 kHz signal to LINE IN and adjust ATT so that output jevel
at LINE OUT indicates 0.42 V (—7dB).
Make recording.
Playback and measure distortion factor of output signal.
When the distortion factor does not satisfy the standard, check the
bias current. When the bias current is lower than standard, distor-
tion will increase.
Care should be exercised in the adjustment because the bias current
also has an influence on the overall frequency response. Refer to
"The overall frequency response” and "The bias current adjustment”
Test tape
Standard value: |
Less than 3.0% (Normal) |
Less than 3.5% (CrO2) |
* LINE IN level contro!
* Bias selector ++++++++- LOW
*EQ
selector
+--+
1
(for
Normal
tape)
| * Bias selector «+--+
*EQ selector -.+..+++
(for CrOz tape)
20uS
12