Service manual

Drive Mechanism GV 30…, GV 50…
k
5 - 30 GRUNDIG Service
Fig. 9.5
9.3 Adjusting the Tape Path
When one of the parts shown in Fig. 9.3 has been removed or replaced,
do not fail to check and adjust the tape path. The tape path is adjusted
while observing the envelope waveform of the video head output
signal.
5050B Supply side
guide roller
5060B Take up side
guide roller
50100 Full
erase head
Guide s
Post
Tape guide
Tape
drum
Tape guide t
7010A Pinch
roller
50700 Load
lever
Capstan shaft
50200 R/P head assy
Fig. 9.3
– Check and correct the setting of the brake band (point 9.1).
– Check and correct the settings of the reel winding torques (point 9.2).
– Connect a dual-channel oscilloscope (trigger channel A) with 10:1
probes as follows (see Adjustment Procedures P. 3-2):
• Channel A: Head switching pulse – test point TP183
• Channel B: FM envelope – test point TP182
– Play the test cassette
– Press the tracking buttons (3) and (4) simultaneously for resetting
the tracking centre.
– Turn the screw (50210) counterclockwise by 20° to 30°. Using a
slotted screwdriver set the X-value (Fig. 9.4) so that the amplitude
of the FM packages is maximum. Fasten the screw (50210) using a
torque of 4.0…5.0kg/cm.
Screwdriver
50210
50200
Fig. 9.4
– Press the tracking buttons (3) and (4) until the amplitude of the FM
packages becomes maximum and flat.
If this adjustment is not successful, adjust the guide rollers
(Pos. 5050B and 5060B) of the left and right threading roller unit with
the adjustment screwdriver so that the amplitude of the FM pack-
ages is as flat as possible.
– Tape rides over the top edge:
turn the left guide roller clockwise
turn the right guide roller clockwise
– Tape rides over the bottom edge:
turn the left guide roller counterclockwise
turn the right guide roller counterclockwise
9.4 Adjusting the A/C Head (Fig. 9.5)
– Turn the screw (50210) counterclockwise by 20° to 30°. Set the X-
value with a screwdriver to obtain the maximum amplitude of the FM
packages. Tighten the screw (50210) using a torque between
4.0…5.0kg/cm.
– The tape must run between the upper edge of the audio head and
the lower edge of the control head. Make sure that the spaces A and
B are the same (Fig. 9.6).
– Connect the oscilloscope to the audio output.
– Play the test cassette with the 400Hz Standard-sound audio signal
recording.
– Set the height adjustment screw for maximum output voltage.
– Play the test cassette with the 8kHz Standard-sound audio signal
recording.
– Set the azimuth adjustment screw for maximum output voltage.
Azimuth adjustment screw
Height adjustment screw
This screw has been preset in the factory
and must not be re-adjusted
Audio head
Control head
A
B
A=B
50200
50210
Fig. 9.6