Grundig GV 900 SV/1 Servise Manual page 93

GV 900..., GV 940...
The torque of the two reels must be higher than 30mNm (306gf-cm).
Otherwise check and clean the following parts of the drive mecha-
nism: Capstan motor shaft (Pos. 61), reel belt (Pos. 34) and limiter
pulley (Pos. 48).
Fig. 28
5.4 Adjusting the Reel Torque in Record / Playback Mode
– Dismantle the cassette compartment (point 3.1).
– Insert the torque cassette meter and observe the notes on operating
the drive mechanism without cassette compartment (point 3.1.1).
– Press button Z in Longplay mode.
– The torque must have an average value of 6.9mNm ±2.5mNm (70
±25gf-cm). Otherwise check the limiter pulley (Pos. 48).
5.5 Adjusting the Torque and Brake Force in Picture Search
Reverse Mode
– Dismantle the cassette compartment (point 3.1) and observe the
notes on operating the drive mechanism without cassette compart-
ment (point 3.1.1).
– Put the torque meter with adapter on to the supply or take-up reel and
set it to 0.
– Press button Å followed by button Ï.
– When carrying out this measurement, turn the torque meter
counterclockwise (one turn every 2-3 seconds).
– The torque of the supply reel must be 14mNm ±3.9mNm (144gf-
cm ±40gf-cm).
Otherwise, check the limiter pulley (Pos. 48).
– The brake force of the take-up reel must be 3.4mNm ±1.5mNm
(35gf-cm ±15gf-cm). Otherwise check the take-up main brake
(Pos. 25).
5.6 Adjusting the Brake Force of the Reel Brakes
– Dismantle the cassette compartment (point 3.1) and observe the
notes on operating the drive mechanism without cassette compart-
ment (point 3.1.1).
– Press button Ì.
When the pinch roller starts to rotate, turn the supply reel until the
drive mechanism automatically moves the pinch roller away from the
capstan.
– Press button ı and, during the drive mechanism is pressing the
reel main brakes against the reels, disconnect the video recorder
from the mains.
– Measure the brake forces of both reels in both senses of rotation with
a torque meter. The measured values must lie within the following
ranges:
– supply reel
clockwise 8.8...23.5mNm (90...240gf-cm)
counterclockwise 3.9...9.8mNm (40...100gf-cm)
– take-up reel
clockwise 3.9...9.8mNm (40...100gf-cm)
counterclockwise 8.8...23.5mNm (90...240gf-cm)
5.7 Adjusting the Pinch Roller Pressure
– Dismantle the cassette compartment (point 3.1) and observe the
notes on operating the drive mechanism without cassette compart-
ment (point 3.1.1).
– Select "Playback - Pause" mode.
– Attach a wire hook (e.g. solid paper clip) to the shaft of the pinch
roller.
– Hook the tension gauge on to the wire hook.
– Press button Å.
– With the tension gauge pull away the pinch roller from the capstan
shaft by an amount that they just do not touch each other any more.
In doing so, the force of pressure must be 8.8Nm...11.8Nm
(900gf-cm...1,2kgf-cm).
GRUNDIG Service
5.8 Adjusting the Tape Path
– Dismantle the cassette compartment (point 3.1) and observe the
notes on operating the drive mechanism without cassette compart-
ment (point 3.1.1).
– Check and adjust the setting of the brake band (point 5.1).
– Check and adjust the torque in picture search reverse mode (point
5.5).
– Connect the dual-channel oscilloscope (triggering channel A) with
the 10:1 probes as follows:
• Channel A: Head switching pulse – test point P201-(2)
• Channel B: FM envelope – test point P201-(1)
– Play the test cassette.
– Loosen the screws (Pos. 202). With the X-value adjustment screw-
driver set the X-value to obtain the maximum amplitude of the FM
envelope. Tighten the screws (Pos. 202).
– With the tracking buttons set the FM envelope to maximum ampli-
tude and flatness.
If this adjustment is not successful, set the guide rollers (Pos. 49) of
the left and right threading roller unit with the adjustment screwdriver
that the amplitude of the FM envelope is as flat as possible.
– The tape rides over the upper edge:
turn the left guide roller clockwise
turn the right guide roller clockwise
– The tape rides over the lower edge:
turn the left guide roller counterclockwise
turn the right guide roller counterclockwise
– With the tilt adjustment screw (Pos. 220, Fig. 30) position the lower
edge of the tape correctly on the guide roller (F Fig. 29) (the tape
must not curl at the lower edge).
500g
Fig. 29
5.9 Adjusting the A/C Head (Fig. 30)
– Loosen the screws (Pos. 202). With the X-value adjustment screw-
driver set the X-value to obtain the maximum amplitude of the FM
envelope.
– Tighten the screws (Pos. 202) with a torque of 0.2Nm (1,5...2,0kgf/
cm).
– Connect the oscilloscope to the audio output.
– Play the test cassette with the 400Hz Standard-sound audio signal
recording.
– Set the height adjustment screw (Pos. 201, Fig. 30) for maximum
output voltage.
– Play the test cassette with the 8kHz Standard-sound audio signal
recording.
– Set the azimuth adjustment screw (Pos. 221, Fig. 30) for maximum
output voltage.
221
202
Fig. 30
Drive Mechanism
61
19
Tape
202
220
201
5 - 13
F