Rec Mute Function Check - Teac C-1 Service Manual

NOTE: The tape must be completely erased prior to this
procedure. Preferably use bulk erased tape.
Numbers in parentheses correspond to steps in Fig. 6-22.
1, Load TEAC MTT-506 test tape.
2. Apply a 125 Hz test signal at -9 dB (274 mV).
3. Place the deck in the record mode for about 30 seconds.
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4. Rewind the tape to the starting point of recording.
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5. Play the tape and measure the output level of the re-
corded portion. Note this reading for temporary referen-
ce level for the following measurements ........ (3)
6. Remove the test tape, turn it over and replace it in the
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7. Play the tape back and read the output level. ..... (5)
8. Get the difference between this reading and the read-
ing previously measured for the 125 Hz signal.
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Fig. 6-22 Adjacent track crosstalk measurement procedure
6-6-1090 REC MUTE FUNCTION CHECK
Specification:
Difference between specific recorded portion and erased
internal portion: 65 dB (min.)
NOTE: For this check, a | kHz narrow bandpass filter
should be used. The test signal delivered from
the AF oscillator should be tuned to the filter
used.
1. Connect the deck and the test equipment as shown in
Fig. 6-9.
2. Load TEAC MTT-506 test tape.
3. Apply and record a 1 kHz signal at +1 dB (0.869 mV)
for several seconds.
4. Push the REC MUTE button so that it will cause the
tape to run with no incoming signal recording for several
seconds.
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5. Push the forward button again to make normal record-
ing for a short duration.
6. Rewind the tape to the original starting point of the
1 kHz signal recorded portion.
7. Play the tape and obtain the output level of both the
recorded portion and the created no signal portion.
8. Measure the output level difference between the por-
tions.
9. A 65 GB difference or more is required.
Specifications:
Variation from reference at 1 kHz: 4dBto7dB
Variation from reference at 10 kHz: 8 dB to 12 dB
(1) 1 kHz recorded w/NR SYSTEM in OUT
1. Connect the deck and the test equipment as shown
in Fig. 6-9.
. Make sure that the NR SYSTEM switch is set in the
OUT position.
. Load a TEAC MTT-506 test tape.
. Apply and record a 1 kHz signal at —29 dB (27.5 mV).
. Rewind and play this recorded section.
. While playing the 1 kHz signal, read the indication of the
output level on the AC voltmeter with the NR SYSTEM
switch at OUT and DOLBY (D0) mark) positions.
7. The output level in the DOLBY position should be 4 dB
to 7 dB lower than the OUT position.
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(2) 1 kHz recorded with NR SYTEM set to OUT and
DOLBY positions.
8. Repeat the above procedure, but record with NR SYS-
TEM switch in OUT then DOLBY positions, and measure
in OUT position. Specification is the same as that of item
(1).
(3) 10 kHz recorded with the NR SYSTEM in the OUT
position.
9. Repeat the above (1) procedure changing the applied
test signal to 10 kHz at —39 dB (8.69 mV).
10. The output level in the DOLBY position should be 8 dB
to 12 dB lower than in the OUT position.
(4) 10kHz recorded with the NR SYSTEM switch in both
OUT and DOLBY positions.
11. Conduct the (2) procedure changing the test signal to 10
kHz at —39. dB. Specification is the same as that for
item (3).
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