Panasonic PV-M2738 Operating, Service Manual

Page: 19 / 151

1-17
DEFEATING THE AUTO TRACKING
To defeat the Auto Tracking Function, place the instrument in
the STOP mode and place a jumper between TP6003 and
TP6009 on the Main C.B.A. The tracking will be placed in the
neutral position.
HOW TO SET TRACKING TO THE
NEUTRAL POSITION
Ejecting the cassette tape and then reinserting it will reset the
tracking to the Neutral position.
CYLINDER ROTATION IN STOP MODE
The cylinder will continue to rotate for approximately 5 minutes
after the STOP button is pressed in Play mode etc. Eject the
tape in order to stop the cylinder.
BLACK SCREWS ON THE CHASSIS
Black Screws are used on the Mechanism Chassis to identify
screws that require adjustment.
HOW TO RESET ALL
COMBINATION VCR MEMORY
FUNCTIONS
To reset (clear) the select language, channel auto set and set
clock functions to their initial power on condition (power on, no
cassette inserted), hold down the PLAY and REWIND buttons
on the unit together for more than 5 seconds.
Power will shut off.
HOW TO CONFIRM AUTO CLOCK SET
FEATURE
1. Connect an RF cable from the output of one unit to the input
of the test unit.
2. Select corresponding RF channels.
3. Playback a recording of P.B.S. channel including clock set
data and confirm this feature.
VARIABLE VOLTAGE ISOLATION
TRANSFORMER
An Isolation Transformer should always be used during the
servicing of Combination VCR whose chassis is not isolated
from the AC power line. Use a transformer of adequate power
rating as this protects the technician from accidents resulting
in personal injury from electrical shocks. It will also protect
Combination VCR from being damaged by accidental shorting
that may occur during servicing.
Also, when troubleshooting the above type of Power Supply
Circuit, a variable isolation transformer is required in order to
increase the input voltage slowly.
Soldering Iron
Presolder
Tweezers
Chip
Soldering Iron
SPECIAL NOTE
All integrated circuits and many other semiconductor devices
are electrostatically sensitive and therefore require the special
handling techniques described under the
"ELECTROSTATICALLY SENSITIVE (ES) DEVICES" section
of this service manual.
REPLACEMENT PROCEDURE FOR
LEADLESS (CHIP) COMPONENTS
The following procedures are recommended for the replacement
of the leadless components used in this unit.
1. Preparation for replacement
a. Soldering Iron
Use a pencil-type soldering iron that uses less than 30
watts.
b. Solder
Eutectic Solder (Tin 63%, Lead 37%) is recommended.
c. Soldering time
Do not apply heat for more than 4 seconds.
d. Preheating
Leadless capacitor must be preheated before
installation. – (266
°
F ~ 302
°
F)
(130
°
C ~150
°
C) for about two minutes.
Note:
a. Leadless components must not be reused after
removal.
b. Excessive mechanical stress and rubbing of the
component electrode must be avoided.
2. Removing the leadless component
Grasp the leadless component body with tweezers and
alternately apply heat to both electrodes. When the solder
on both electrodes is melted, remove the leadless compo-
nent with a twisting motion.
Note:
a. Do not attempt to lift the component off the board until
the component is completely disconnected from the
board by a twisting action.
b. Be careful not to break the copper foil on the printed
circuit board.
Fig. 8-1
3. Installing the leadless component
a. Presolder the contact points on the circuit board.
Fig.8-2