Sony TC-366 Service Manual page 31

12-15. Dummy Coil Adjustment
Connection:
As shown in Fig. 12-22.
Adjusting Parts:
T0306 203) sete tne heehee: See Fig. 12-2
Switch Settings:
MONITOR switch ..............0..00 TAPE
TAPE SPEED switch ......0...0.0.... 19 cm/s (7% ips)
VR Setting:
AUX VOLUME............. indicated on page 25
Procedures:
(1) Thread a blank tape.
(2) Deliver a 20 kHz signal of -30dB (24.5 mV)
into the L-CH (R-CH) AUX INput jack and
place the machine in stereo-record mode.
(3) Memorize the VTVM reading.
(4) Set the L-CH (R-CH) in record mode.
(5) Adjust L203 (L103) with a non-magnetic
screw driver, taking care not to break the
core so that the VITVM reading is the same
as the reading obtained in preceding pro-
cedure (3).
AF tape, blank
OSC REC Amp.
VTVM
_
AUX
20 kHz
-30dB
LINE OUT
Fig. 12-22 Dummy coil adjustment setup
12-16. Erase Ratio Measurement
Connection:
As shown in Fig. 12-23.
Switch Setting:
MONITOR switch ......... TAPE
VR Setting:
AUX VOLUME.............. indicated on page 25
Procedures:
(1) Thread a blank tape.
(2) Deliver a 1kHz signal of +10dB (2.5V)
into the AUX INput jack and record the
signal on the blank tape.
(3) Rewind the tape and erase a part of the
recorded tape (record mode with no signal
input).
(4) Memorize the VIVM_ reading on the
recorded part and the erased part of the
tape.
Be sure that the ratio of the recorded part
to the erased part in level is more than
65 dB.
If not, check the tape pass adjustment and
that the erasing current is 80~120mA.
To measure the erasing current, connect the
two 1 resistors in series to the erase head
as shown in Fig. 12-24 and the VTVM across
the 19 resistor.
Be sure that the VTVM reading is 80~
120 mV.
Note: Take impedance-matching correctly for the band-
pass filter.
(S
~
REC Amp.
AF tape, blank vivM
OSC =o
AUX
1kHz, +10dB
LINE OUT
Fig. 12-23 Erase ratio measurement setup
head, erase
Fig. 12-24. Erasing current check setup