Ensure that the tape path is clean before using the test
tape.

Test Tape. (30 Minutes running time)

RESOLUTION

The 3Mhz resolution lines should be visible.

HEAD SWITCHING POINT

The head switching point has been artificially generated
1/3 of the way down the screen. Adjust the head
switching point so it coincides with the horizontal line
"switching point" as marked on the cassette case picture.
(With someVCR's this line can disappear, this is normal.)
When the switching point differs 2 lines or more it should
be adjusted.

BACK TENSION

The vertical line seen in the centre of the test pattern is
used to gauge the amount of back tension.When the
vertical line pulls past the left hand marker line with arrow
head, the back tension is too high.When the vertical line
pulls past the right hand marker line with arrow head the
back tension is too low. (See picture on cassette cover
with points marked A and B.)

AUDIO/SYNCH. HEAP ADJUSTMENT

• Sound (=1 kHz):

Adjust azimuth and head height for maximum sound
level. Check that the tilt angle is correct

• Tracking:

The user tracking control should be in the centre
position.The automatic tracking control should be
switched off or disabled. Adjust the horizontal position
of the head so that the video envelope reaches the
maximum level (use anoscilloscope) whilst also
observing the test pattern. Adjust the horizontal
position until the vertical line in the centre of the screen
is no longer displayed double at the top.

HEAD MOUNTING

The first minute of this tape is in black and white, the rest
of the tape is in colour. If this is not the case, the head has
been fitted 180 degrees out of phase and should be
reversed.

VIDEO HEAD TESTS

(Refer to the test patterns on the cassette cover.)

FIELD 1

The "drop-out compensation" should replace the missing
lines. In the best case vertical black and white lines will
appear in this field. In the worst case only noise will be
visible. A low FM-level will mainly be seen in the drop-out
compensation, as a result of dirt, wear on the video head
or head-gain not correctly adjusted.

FIELD 2

There should be no interference below the black bars.
When lines appear in field 2 the picture can still be judged
as good or at least reasonable. The less interference the
better.

FIELDS

Should not display any interference. When any lines occur

in this field it

means-that the video head is beginning to wear. The

tracking control can be used to check that the best

picture has been achieved in all fields. If the tracking

control setting deviates too much

from the center position the audio/sync adjustment

should be repeated. In some cases it is not possible to

make a good diagnosis as a good picture can also have

drop-outs.

VIDEO HEAD-GAIN/RESONANCE ADJUSTMENTS

The following is only for VCR's that have head gain/head
resonance adjustments.

These adjustments are normally only done after the video
head has been replaced.

THE FOLLOWING FIELDS ARE USED FOR THE
ADJUSTMENT

1. Resolution lines

2. Black to White and White to Black changeovers

3. Fields! to 3

PREPARATION

• A scope has to be connected to the FM waveform
testpoint

• The tape guides should have been adjusted correctly

• The user tracking control should be in the centre

position

Mark the present positions of the head gain and head
resonance controls, so that the starting position can
always be found for the next adjustment.

• Head gain Adjustment.

First, the level of the FM waveform has to be adjusted to
the maximum, then adjusted for waveforms of the same
level.

• Head resonance adjustment.
If two controls are available to adjust the head
resonance, use the controls in turn in order to achieve
the best result. You will be able to see this best by
looking at that part of the test image which changes
from white to black. Sometimes it is necessary to lower
the4evelof the FM waveform to get the best results.
One has to watch the picture sharpness carefully. The 3
MHz lines have to be clearly visible.