Note:
Before
measuring
and
adjusting,
the
overall
frequency
response make sure of the playback frequency response (For
the method of measurement, please refer to the playback fre-
quency response).
Overall frequency response chart (Normal)
PTT
——
eH
Nae
|
|
|
---++3dB
+2dB1
+20B
odB+—
0dB
—2dB
—2dB
—4d0B
7
-30B
—6dB
(Recording equalizer is fixed)
. Make connections as shown in fig. 11.
. Place UNIT into normal tape mode and insert the normal
reference blank test tape (QZZCRA).
. Supply a 1kHz signal from the AF oscillator through ATT to
LINE IN.
. Adjust ATT so that input level is -20dB below standard
recording level (standard recording level =O VU).
. Adjust the AF oscillator frequency to 1kHz, 50Hz, 100Hz,
200Hz, 500Hz, 4kKHz, 8kHz, 10kHz and 12.5kHz signals,
and record these signals on the test tape.
. Playback the signals recorded in step 6, and check if the
frequency response curve is within the limits shown in the
overall frequency response chart for normal tapes (fig. 10).
(If the curve is within the charted specifications, proceed
to steps 7, 8 and 9.)
If the curve is not within the charted specifications, adjust
as follows;
a
i
= 28)
:
63Hz
100Hz
200Hz
500Hz
1kHz
2kHz
5kHz 10kHz 12.5kHz
VRQ (L-CH)
{vaio (R-CH)
LINE IN
OSC Playback LINE OUT
/record mode
0
°
SO
VTVM
Oscilloscope
piace
Saco ee
For overall frequency
VIVM Oscilloscope recoonse measurement
Record/
Ae
alate
For bias voltage
Measurement
Fig. 11
Adjustment (A):
When the curve exceeds the
FF
overall specified frequency
response
chart (fig. 10) as
shown in fig. 12.
1) Increase bias current by 5
Adjustment (B):
When the curve falls below
the
overall
specified
fre-
quency response chart (fig.
10) as shown in fig. 13.
1) Reduce
bias current
by
turning VRQ (L-CH) and H-—
VR10 (R-CH).
(See fig. 1.)
Repeat steps 5 and 6 for
confirmation (Proceed to
kHz
9kHz
6 kHz 7 kHz 8kHz
turning
VRQ
(L-CH) and
VR10 (R-CH).
Repeat steps 5 and 6 for
confirmation (Proceed to
steps 7, 8 and 9 if the
kHz
kHz
6 kHz 7kHz 8kHz
curve
is now
within the
charted specifications as
shown fig. 10.)
If the curve still falls below the charted specifica-
tions (fig. 10), reduce
bias current further and
repeat steps 5 and 6.
steps 7, 8 and
9 if the
curve
is now
within the
charted specifications as shown fig. 10.)
If the curve still exceeds the specifications (fig.
10), increase
bias
current
further
and
repeat
steps 5 and 6.
. Place UNIT into CrO, tape mode.
. Change
test
tape
to CrO,
reference
blank
test
tape
(QZZCRX), and record 1kHz, 50Hz, 100Hz, 200Hz, 500Hz,
4kHz, 8kHz, 10kHz and 15kHz signals.
Then, playback
the signals and check
if the curve
is within the limits
shown in the overall frequency response chart for CrO, , <4,
tapes (fig. 14).
eAd8
ime
. Place UNIT into metal tape mode and change test tape to , 54,
|
metal
reference
blank test tape (QZZCRZ),
and
record
44,
1kHz, 50Hz, 100Hz, 200Hz, 500Hz, 4kHz, 8kHz, 10kHzZ, _54,
12.5kHz and 15kHz signals.
Then, playback the signals _,,,
and check if the curve is within the limits shown
in the _¢q3
overall frequency response chart for metal tapes (fig. 14).
. Confirm
that bias currents are approximately as follows
when the UNIT is set at different tape mode.
eRead
voltage on VTVM
between
ground and test point
(TP1 for L-CH, TP2 for R-CH) and calculate bias current by following formula:
Value read on VTVM (V)
10 (Q)
around 400,A (Normal position)
Standard value: around 500A (CrO, position)
around 800,,A (Metal position)
Overall frequency response chart (CrO,, Metal)
+
eel
500Hz
1kHz
2kHz
Fig. 14
50HzZ
100Hz
200Hz
5kHZ
10kHz 15kHz
Bias current (A) =
