Mechanical Adjustments; Electrical Adjustments; Torque Measurement; Standard Input Level - Sony tc-tx77 Service Manual

SECTION 3

MECHANICAL ADJUSTMENTS

PRECAUTION
1. Clean the following parts with a denatured-alcohol-moistened
swab:
record/playback/earth head pinch roller
rubber belts
idlers
2. Demagnetize the record/playback head with a head demagne-
tizer. (Do not bring the head demagnetizer close to the erase
head.)
3. Do not use a magnetized screwdriver for the adjustments.
4. After the adjustments, apply suitable locking compound to the
parts adjusted.
5. The adjustments should be performed with the rated power
supply voltage unless otherwise noted.

Torque Measurement

Mode Torque Meter
FWD
CQ-102C
FWD
Back tension
REV
CQ-102RC
REV
Back tension
FF, REW CQ-201B
capstan
Meter Reading
30 – 65 g•cm
(0.42 – 0.90 oz•inch)
1.5 – 6 g•cm
(0.021 – 0.083 oz•inch)
30 – 65 g•cm
(0.42 – 0.90 oz•inch)
1.5 – 6 g•cm
(0.021 – 0.083 oz•inch)
70 – 130 g•cm
(0.98 – 1.80 oz•inch)
– 7 –
SECTION 4

ELECTRICAL ADJUSTMENTS

PRECAUTION
1. The adjustment should be performed in the publication.
(Be sure to male playback adjustment at first.)
2. The adjustments and measurement should be performed for
both L-CH and R-CH.
• Switch position
DOLBY NR switch
DIRECTION switch
• Standard record position
Deliver the standard input signal level to input jack and set
the REC LEVEL (RV301) control to obtain the standard
output signal level as follows.
– Record Mode –
AF OSC
10 k Ω
attenuator
600 Ω
LINE IN

Standard Input Level

Input terminal
source impedance
input signal level
Standard Output Level
Output terminal
load impedance
output signal level
Test Tape
Type Signal
P-4-A100 10 kHz, – 10 dB
P-4-L300 315 Hz,
WS-48B 3 kHz,
0 dB = 0.775 V
Test Mode
With the POWER turned OFF, short the test point CN801 (2P) on
the SYSTEM CONTROL board (making IC801 pin !º "L") and
turn the POWER ON. Thus, the TEST mode will be activated.
If a recording is done in the TEST mode, the REC MEMORY
mode becomes active where the tape is rewound by the amount of
recording when a rewinding is executed after recording.
After adjustment, make the CN801 (2P) open to release the TEST
mode.
: OFF
: A
level meter
47 k Ω
+
set
–
LINE OUT
LINE IN
10 kΩ
0.5 V (– 3.8 dB)
LINE OUT (L-CH)
47 kΩ
0.5 V (– 3.8 dB)
Used for
Azimuth Adjustment
0 dB PB Level Adjustment
0 dB Tape Speed Adjustment