Sony TC-K670 - Electrical Adjustment Procedures; Tape Speed and Bias Current Adjustment; Playback Level and Record Bias Adjustment

Tape Speed Adjustment
Setting:
Test pin CNE707: short
Procedure:
Mode: playback
test tape
WS-48B
(3 kHz, 0 dB) frequency counter
LINE OUT
1. Set to FWD playback mode.
2. Adjust motor rear side (variable resister) so that the frequency
counter reading becomes 3,000 + 15 Hz.
Adjustment Location: motor rear side
variable resister
Playback Leve! Adjustment
Procedure:
Mode: playback
test tape
P-4-L300
(315 Hz, 0 dB)
LINE OU
Adjust RV121 (L-ch) and RV221 (R-ch) so that the reading on VTVM
meets the adjustment limits below.
Adjustment Limits:
LINE OUT level: — 5 + 0.5 dB (0.41 — 0.46 V)
Level difference between channels: less than 0.5 dB
Check that the LINE OUT level does not change even if Playback and
Stop operation is repeated several times.
Adjustment Location: MA I N (A) board
Bias Consumption Current Adjustment
Procedure:
LINE IN
(no signal)
CS-412 blank tape
digital voitmeter
i=
47 kQ
CNE521
B+ (4+7.7 V)
1. Set RV181 and RV281 to mechanical center and turn the set
recording mode.
2. Connect digital voltmeter as shown by the following table.
3. Adjust the following transformers for the minimum readings on the
digital voltmenter.
|__| Mesurement Point _| Adjustment Part
® and @, CNES21 7181 not more than
R-ch | _@and © CNED2 1281 200nV
Adjsutment Location: MA | N (A) board
Record Bias Adjustment
Setting:
REC LEVEL control: Standard Record (see page 12).
test pin CNE707: short
Procedure:
1. Mode: record
AF OSC
10 kQ CS-122 blank tape
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attenuator
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6
Il! oo°o
A
reernrenmnerrenned
LINE IN
Yio
he,
p3t-
6aV(-27.
8d)
2.
Mode:
playback
recorded
a
portion
LINE OUT
Playback the signal recorded in step 1.
Confirm that the 10 kHz playback output is 0 + 0.5 dB relative to the
315 Hz output. If necessary, adjust RV181 (L-ch) and RV281 (R-ch) for
repeat the steps given above.
Adjustment Location: Audio system control (A) board