Mechanical Adjustments; Electrical Adjustments; Test Mode; Tape Deck Section - Sony XR-4790 Service Manual

SECTION 4

MECHANICAL ADJUSTMENTS

1. Clean the following parts with a denatured-alcohol-moistened
swab:
playback head
rubber belt
idlers
2. Demagnetize the playback head with a head demagnetizer.
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 power supply
voltage unless otherwise noted.
• Torque Measurement
Mode Torqu Meter
Forward CQ-102C
Forward
CQ-102C
Back Tension
Reverse CQ-102RC
Reverse
CA-102RC
Back Tension
FF, REW CQ-201B
• Tape Tension Measurement
Mode Torqu Meter
Forward CQ-403A
Reverse CQ-403R
pinch roller
capstan
Meter Reading
30 - 65 g•cm
(0.42 - 0.90 oz•inch)
0.5 - 4.5g•cm
(0.01 - 0.06 oz•inch)
30 - 65 g•cm
(0.42 - 0.90 oz•inch)
0.5 - 4.5g•cm
(0.01 - 0.06 oz•inch)
60 - 200 g•cm
(0.83 - 2.78 oz•inch)
Meter Reading
more than 90 g
(more than 3.18 oz)
more than 90 g
(more than 3.18 oz)

ELECTRICAL ADJUSTMENTS

TEST MODE

This set have the test mode function. In the test mode, FM Auto
Scan/Stop Level and AM (MW) Auto Scan/Stop Level adjustments
can be performed easier than it in ordinary procedure.
<Set the Test Mode>
1. Set the "power select" switch (S801) is "A" position.
2. Turn ON the regulated power supply. (All LEDs on the set
lights up, and the clock is displayed.)
[OFF]
Note: Press the
[4]
3. Push the preset
[5]
4. Push the preset
[1]
5. Press the preset
6. Then the display indicates all lights, the test mode is set.
<Release the Test mode>
[OFF]
1. Push the button.
2. Return the "power select" switch (S801) to initially set posi-
tion.
See the adjustment location from on page 16 for the
adjustment.

TAPE DECK SECTION

Tape Speed Adjustment
Setting:
test tape
WS-48A
(3 kHz, 0 dB)
set
Procedure:
1. Put the set into the FWD PB mode.
2. Adjust adjustment resistor for inside capastan motor so that
the reading on the speed checker or frequency counter becomes
in specification.
Specification: Constant speed
Speed checker
–1.5 to +2.5%
Adjustment Location: See page 16.
– 13 –
SECTION 5
button, if the clock is not displayed.
button.
button.
button for more than two seconds.
0 dB= 0.775 V
speed checker
or
frequency counter
10 k Ω
– +
LINE OUT
Frequency counter
2,955 to 3,075Hz