Erase Head - Philips VR109/55 Service Manual

www.freeservicemanuals.info
6. Press CH DOWN button on the VCR until the CTL
waveform has shifted from its original position (not
the position achieved in step 5, but the position of
CTL waveform in step 4) by approximately
-2msec. Make sure that the envelope is simply at-
tenuated (shrinks in height) once CTL waveform
passes its original position and is further brought
in the minus direction.
7. Set the Tracking Control Circuit to the center posi-
tion by pressing the CH UP button and then the
PLAY button on the VCR.
1-C. Checking/Adjustment of Envelope
Waveform
Purpose:
To achieve a satisfactory picture and precise tracking.
Symptom of Misalignment:
If the envelope output is poor, noise will appear in the
picture. The tracking will then lose precision and the
playback picture will be distorted by any slight variation
of the Tracking Control Circuit.
1. Connect the oscilloscope to TP301 (C-PB) on the
Main CBA. Use TP302 (RF-SW) as a trigger.
2. Play back the Gray Scale on the Alignment Tape
(FL6N8). Set the Tracking Control Circuit to the
center position by pressing the CH UP and then
the PLAY button on the VCR. Adjust the height of
Guide Rollers [2] and [3] (Fig. M3, Page 2-3-3)
watching the oscilloscope display so that the enve-
lope becomes as flat as possible. To do this adjust-
ment, turn the top of the Guide Roller with the
Guide Roller Adj. Screwdriver.
3. If the envelope is as shown in Fig. M7, adjust the
height of Guide Roller [2] (Refer to Fig. M3) so
that the waveform looks like the one shown in Fig.
M9.
4. If the envelope is as shown in Fig. M8, adjust the
height of Guide Roller [3] (Refer to Fig. M3) so
that the waveform looks like the one shown in Fig.
M9.
5. When Guide Rollers [2] and [3] (Refer to Fig.M3)
are aligned properly, there is no envelope drop
either at the beginning or end of track as shown in
Fig. M9.
Note: Upon completion of the adjustment of Guide
Rollers [2] and [3] (Refer to Fig. M3), check the X Value
by pushing the CH UP or DOWN buttons alternately, to
check the symmetry of the envelope. Check the number
of pushes to ensure center position. The number of
pushes UP to achieve 1/2 level of envelope should
match the number of pushes DOWN from center. If
required, redo the "X Value Alignment."
06/28/2012
1-D. Azimuth Alignment of Audio/Control/

Erase Head

Purpose:
To correct the Azimuth alignment so that the Audio/Con-
trol/Erase Head meets tape tracks properly.
Symptom of Misalignment:
If the position of the Audio/Control/Erase Head is not
properly aligned, the Audio S/N Ratio or Frequency
Response will be poor.
1. Connect the oscilloscope to the audio output jack
on the rear side of the deck.
2. Play back the alignment tape (4822 397 10057) and
confirm that the audio signal output level is 6 kHz.
3. Adjust Azimuth Adj. Screw so that the output level
on the AC Voltmeter or the waveform on the oscil-
loscope is at maximum. (Fig. M6)
Dropping envelope level at the beginning of track.
Dropping envelope level at the end of track.
Envelope is adjusted properly. (No envelope drop)
2-3-4
World of Free Manuals
Fig. M7
Fig. M8
Fig. M9
H67T0MA