Technics RS-M04 Service Manual

ITEM MEASUREMENT & ADJUSTMENT
@® Overall frequency
response
Condition:
* Record/playback mode
* Normal tape mode
* Fe-Cr tape mode
* CrO2 tape mode
* Metal tape mode
* Input level controls ---- MAX
* Output level control ++» MAX
* Standard input Jevel
MIC +-+-++ —72+3.5dB
LINE IN «+» —24+3.5dB
Equipment:
*VTVM_ * AF oscillator
*ATT + Resistor (600Q)
* Test tape
(reference blank tape)
+++ QZZCRA for Normal
++ QZZCRX for CrO2
-++QZZCRY for Fe-Cr
++ QZZCRZ for Metal
Note:
Before measuring and adjusting, make sure of the playback
frequency response (For the method of measurement, please 2 Leper
refer to the playback frequency response). aon LINE IN Test tape
1. Test equipment eee is shown in fig. 38.
2. Place the test tape (QZZCRA) in the cassette holder. crag ele
3. Set UNIT into record mode, and normal tape mode. Fo] The: oO]
4. Supply 1kHz signal from AF oscillator through ATT to Test tape Payback mode VTVM Oscilloscope
LINE IN. Fig. 38
. Adjust ATT so that input level is
—20dB below standard recording
level (standard recording level =O VU).
. At this time, LINE OUT level indicates
0.07 V.
. Record each frequency 50Hz, 70Hz,
600 Hz, 1kHz, 2kHz, 8kHz, 10 kHz,
and 12kHz (14kHz for CrO2, Fe-Cr
and Metal).
. Playback and express in dB the
difference between playback output
level of each frequency based on
playback output level of 1 kHz.
. Make sure that the measured value Overall frequency response chart
is within the range specified in the (Fe-Cr, CrO2, Metal)
overall frequency response chart
(shown in fig. 30). 50 Hz /0Hz
. Change test tape to Fe-Cr (QZZCRY),
CrOz (QZZCRX) and Metal (QZZCRZ).
. Set UNIT into each tape mode.
. Measure as same as manner from
step (3) to step (8).
. Make sure that the measured value
is within the range specified in the
overall frequency response chart for
Fe-Cr, CrO2 and Metal tape shown
in fig. 31.
R/P head
Overall frequency response chart (Normal)
12kHz
200 Hz 600 Hz
Adjustment-using bias current
1. When the frequency response between the middle and high
frequency range becomes higher than the standard value,
as shown by the solid line in fig. 41 increase, refer to bias
current adjustment.
. When it becomes lower, as shown by dotted line, refer to
bias current adjustment. . Fig. 41
1kHz ——(2kHz j 8kHz 12kHz
Bias current adjustment VR201 (L-CH)
1. Test equipment connection is shown in fig. 42. viene eee Seach as
2. Set UNIT into record mode, and normal tape mode. s
3. Read voltage on VTVM and calculate bias current by following
formula: ;
Value read on VTVM (V) VIVM Oscilloscope
10 (Q)
Bias current (A) =
Standard value: around 350uA (Normal tape mode) |
. If measured value is not within standard, adjust VR201 (L-CH) and VR202 (R-CH).
. Set the tape selector to each position.
. Make sure that the measured value is within standard.
Standard value: around 370A (Fe-Cr tape mode)
around 440A (CrO2 tape mode)
around 700zA (Metal tape mode)
10

Technics RS-M04 Specifications

General

Brand	Technics
Model	RS-M04
Category	Cassette Player
Language	English