Panasonic OmniVision PV-M1347, Service Manual

Page: 38 / 143

2-20
BACK TENSION CONFIRMATION
Purpose:
To fine adjust the Back Tension so that the tape runs
smoothly with a constant tension.
Symptom of Misadjustment:
1) If the tape tension is less than the specified value, the
tape cannot come into proper contact with the Video
Heads, resulting in poor picture playback.
2) If the tape tension is too high, the tape will soon be
damaged.
Measurement Procedure
Equipment Required:
Back Tension Meter (Made in U.S.A., Purchase Locally)
VHS Cassette Tape (120-Minute Tape)
Specification ........................................................ 25 +/- 2.5g
1. Play back a T120 cassette tape from the beginning for
approx. 10 to 20 seconds to stabilize tape movement.
2. Insert a Tension Meter into tape path and measure the back
tension.
3. If the reading is out of specification, make sure that there is
no dust or foreign material between the Tension Band of
Tension Arm Unit and the Reel Table.
If cleaning does not correct the tension measurement,
replace the Tension Spring and the Tension Arm Unit.
Fig. M3-1
Note:
1) Be sure that the three probes of the meter are all in solid
contact with the tape, but not touching any other parts of
the mechanism.
2) It is recommended that measurements be repeated at
least three (3) times because the tension meter is very
sensitive to external vibrations.
Probes of Gage
P1
P2
FE Head
Fig. M3-2
Tension
Spring
Tension
Arm Unit
S Spring Arm
Right Post (Use this post only.)
Left Post
Tension Band
S Reel
Table
The Left Post will be deleted on running
change basis.
DO NOT attach the Spring to the Left
Post.
CAUTION: