5-15
DNW-A22/A22P
0
0
(Ex, Ha=2)
(Ex, Hb=40)
40
Dial gauge
Dial gauge
Video head A
Probe
Video head A
Probe
< A >
< B >
Hr = Hb
_
Ha
= 40
_
2
= 38 (µm)
Measurement of Head Tip Protrusion
n
When turning the upper drum manually, hold the cover of
the measurement gauge by your hand to not come to turn
the gauge with the drum rotation.
1.
Turn the upper drum manually counterclockwise (
3
)
very slowly to approach a video head aside of the
probe. (Refer to <A> in Figure 4.)
2.
Read the dial gauge pointer. (= Ha)
n
The scale of the dial gauge is 2
µ
m (0.002 mm) pitch.
Clockwise:
+
. Counterclockwise:
_
.
3.
Turn the upper drum manually counterclockwise (
3
)
very slowly to center the video head in the probe.
(Refer to <B> in Figure 4.)
4.
Read the dial gauge pointer. (= Hb)
5.
Calculate the real head tip protrusion Hr with the Ha
and Hb.
Hr = Hb
_
Ha
6.
Calculate the head tip protrusion Hr for all heads with
steps 1 through 5 performing .
7.
Measure and calculate the real head tip protrusion Hr
for all heads again.
n
Do it two times for fear of measuring error.
Figure 4. Example of Head Tip Protrusion Measurement
This table is in measure order of the heads.
Head tip protrusion (Hr = Hb
_
_
_
_
_
Ha)
Head
Spec.
name
(
µ
m)
First time
Second time
Dummy
_
(No need for measurement)
A4 dummy
*
_
(No need for measurement)
B4 dummy
_
(No need for measurement)
Y-A
20
=
_
|
=
_
C-A
20
=
_
|
=
_
PB A6
22
=
_
|
=
_
PB B6
22
=
_
|
=
_
Dummy
_
(No need for measurement)
A8 dummy
*
_
(No need for measurement)
B8 dummy
_
(No need for measurement)
Y-B
20
=
_
|
=
_
C-B
20
=
_
|
=
_
PB
A2
22
=
_
|
=
_
PB
B2
22
=
_
|
=
_
*
: A4 and A8 dummy heads are equiped in former upper drum assembly.
Removal of Head Tip Protrusion Measurement
Gauge
1.
Turn the upper drum manually counterclockwise (
3
)
very slowly to move a video head aside from the
probe.
2.
Loosen the adjustment screw fully (by turning it
counterclockwise).
3.
Lift up the positioning flange from the outer circum-
ference of the drum’s upper surface to a few millime-
ters, and then lift the measurement gauge slowly and
remove it while pushing two legs against the outer
circumference of the drum’s upper surface (applying
force slightly to the measurement gauge in the direc-
tion indicated by arrow A). (Refer to Figure 3.)
n
Perform carefully and slowly so that the probe of a
measurement gauge does not touch the outer circum-
ference or video head on the drum.
5-3. Video Head Tip Protrusion Check
