Playback Frequnecy Response; Erase Current Adjustment; Overall Gain Adjustment And Overall Frequency Response - Technics RS-TR979 Service Manual

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RS.TR979
PLAYBACK FREQUENCY RESPONSE (DECK 1/2)
1. Playback the frequency response portion (315Hz, 12.5kHz-
63Hz, -20dB) of the test tape (QZZCFM).
2. Assure that the frequency
shown in Fig. 6 for both L-CHand R-CH.
0
~
0
0
ERASE CURRENT ADJUSTMENT (DECK
1. Insert the Metal. blank test tape (QZZCRZ)and set the unit to
the Record Pause mode.
2. Check if the output at this time between the erase current
confirmation point Deck 1=TP351 (Deck 2=TP301) and GND
(chassis) (the output
2=R308)) is within the standard value.
Standard value: 180:t20mA (Metal)...EVM Reading: 180:t20mV
OVERALL GAIN ADJUSTMENT AND OVERALL
FREQUENCY RESPONSE (DECK 1/2)
1. Load a Normal blank test tape (QZZCRA)into the deck under
test. Press the ATC button, then the REC button. (At this
point the deck automatically
frequency response.)
With the deck placed in Record. Pause mode, apply the
2.
reference test signal (1kHz) to the Rec. input and adjust the
output level to 320mV with the attenuator (ATT). After this,
start recording.
3. While playing back the reference signal just recorded, veri~y
that the output level falls in the following range.
Standard value: 320mV:tO.5dB
I
4. Apply test signals
covering the range from 50Hz to 10kHz) whose levels are
20dB lower than the reference signal level (1kHz) to the Rec.
input and record these signals in sequence.
5. Play back the test signals just recorded and verify that the
levels at the test frequencies fall in the ranges specified in
Fig. 8 with respect to the reference signal level.
6. Repeat steps 4 and 5 above for CrO2blank test tape (QZZCRX)
and Metal blank test tape (QZZCRZ), in these cases raising
the upper end of the test signal frequency range to 12.5kHz.
Verify that the signal levels at the test frequencies fall in the
ranges specified in Fig. 9 with respect to the reference signal
level.
7. Perform the same checks for both DECK1 and DECK2.
Steps 1 through 4 above are concerned with overall gain;
steps 5 through 7 pertain to overall frequency response.
response is within the range
~
'
::::
-
- (@}.J)
..
"~' ""'
EVil
Fig. 5
1/2)
on both edges of Deck 1
adjusts the overall gain and
I
(with the specified test
Fig. 10
+6dB'
+4dB
-- -
+3dB'
+2dB
Ode
I
-2dB'
--
-3dB
-4dB
-6dB
63Hz 100Hz 200Hz
ERASE HEAD
=
R358 (DECK
Norma' Overall frequency respon..
+6dB
+4dB
+2dB
Ode
-2dB
-4dB'
-6dB
50HZ 100Hz 200Hz
crOz Meta' Overall frequency respon..
+6dB
+4dB
frequencies
+2dB
I
I
Ode
-2dB
-4dB
-6dB
50HZ 100Hz 200Hz
-16-
"
./:
I
I
I
I
:
'
500Hz
1kHz 2kHz 4kHz
315HZ
Fig. 6
IIil!II
DECK1:
IIil!II
DECK2:
Fig. 7
chart (NR OUT)
...
./
............
./'
500Hz 1kHz 2kHz
Fig. 8
./"
............
l./'
500Hz 1kHz 2kHz
Fig. 9
-
+5dB
- -
+3dB
+2dB
Ode
2dB
-
3dB
-
-5dB
,
12.5kHz
8kHz
+.
EVM
(Electronic
Voltmeter)
+4dB
Ode
- -
-3dB
10kHz
chart (NR OUT)
f- -
+5dB
f-
I
Ode
-4dB
I
I
,
12.5kHz