Sony TC-KB920S - Tape Speed and Bias Adjustments; Tape Speed, Playback Level, and Bias Adjustments

– 11 –
Tape Speed Adjustment
Procedure:
Mode: playback
1. Set to FWD playback mode.
2. Adjust RV71 so that the frequency counter reading becomes
3,000±90 Hz.
3. Frequency difference between the beginning and the end of
the tape should be within 3%.
Adjustment Location: AUDIO board (See page 12.)
Sample value of Wow and Flutter: 0.3% or less W.RMS (JIS)
(WS-48B)
Playback Level Adjustment
Procedure:
Mode: playback
Adjust RV121 (L-CH) and RV221 (R-CH) so that the reading on
level meter meets the adjustment limits below.
Adjustment Limits:
LINE OUT level: –7.7±0.5 dB (0.301 to 0.338 V)
Level difference between channels: within 0.5 dB
Check that the LINE OUT level does not change even if Playback
and Stop operation is repeated several times.
Adjustment Location: MAIN board (See page 12.)
+
–
set
LINE OUT
frequency counte
r
test tape
WS-48B
(3 kHz, 0 dB)
47 k Ω
+
–
set
LINE OUT
47 k
Ω
test tape
P-4-L300
(315 Hz, 0 dB)
level mete
r
Bias Consumption Current Adjustment
Procedure:
1. Set RV103 (L-CH) and RV203 (R-CH) 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 voltmeter.
Measurement Point Adjustment Part Value
L-CH 2 and 3, TP321 T101
minimum
R-CH 1 and 2, TP321 T201
Adjustment Location: MAIN board (See page 12.)
Record Bias Adjustment
Setting:
REC LEVEL control: Standard Record (See page 10.)
Procedure:
1. Mode: record and playback
2. Adjust RV103 (L-CH) and RV203 (R-CH) so that 10 kHz play-
back output is 0±0.3 dB relative to the 315 Hz output.
Adjustment Location: MAIN board (See page 12.)
–
+
set
LINE IN
(no signal)
B+ (+7.5 V)
TP321
3
2
1
L-CH
R-CH
47 k Ω
digital voltmete
r
CS-413 blank tape
set
47 k
Ω
AF OSC
Attenuator
LINE IN
315 Hz
10 kHz
50 mV (–23.8 dB)
600
Ω
10 k Ω
CS-123
blank tape
LINE OUT
level meter
+
–