Grundig GV 411-2 Service Manual page 30

Abgleich / Adjustment Procedures
2.4 Family Board – Audio (AF)
Test equipment / aids: AF Millivoltmeter, AF Generator, branded Video Cassette.
Service work after replacing the Family Board, the RP Head or the Erase Head: Adjustment no. 1.1, 2
Adjustment
1. Erase Frequency, Frequency counter: ............................................. 1918-(7)
F5603 Record
1.1 Bias, R3618 AF millivoltmeter: ................................................... R3600
Record
1.2 Frequency – Feed an audio signal of 200mV
Response Test generator to the EURO-AV1 socket, contact 2 or 6.
– Make a recording of 400Hz and 8kHz each of 1 minute at
least. Afterwards play back these recordings (in doing so
switch over to Standard Sound "MONO").
– Connect an AF millivoltmeter (oscilloscope) to EURO-AV1
socket, contact 1 or 3.
2. Standard Sound - AF generator (1kHz / 0.7V
Playback Level ................................ EURO-AV1 socket, contact 2 and 6
AF millivoltmeter: .............. EURO-AV1 socket, contact 1
Record (Normal Play).
Play back this recording (in doing so switch over to Stan-
dard Sound "MONO").
Call up the Service Function: Press the "STOP" button on
the remote control and then the "play" button on the video
recorder and hold them down for at least 5 s.
3. Keyboard Control Unit (ODCE1)
Test equipment: Frequency Counter
Service work after replacing the Keyboard Control Unit: –
Adjustment
1. Clock, C2005 Disconnect the VCR from the mains.
IC7101: ....... Connect Pins 67 and 68 with Pin 33 (+5V).
Frequency Counter: ............................................ 1101-(1)
Reconnect the VCR to the mains.
3 - 6
Preparation
(480mV ) from the AF
rms PP
):
rms
Preparation
Adjustment Procedure
With F5603 set the reading on the frequency
(Erase Oscillator)
±
counter to 70kHz 10kHz.
Set the voltage drop across R3600 with R3618
15mV .
rms
Check the frequency response.
The voltage ratio of 400Hz to 8kHz must not be higher than
1: 0.7 or 0.7:1 (±3dB). If the voltage ratio exceeds these
limits, the bias must be altered:
To increase the playback voltage at 8kHz: Reduce "BIAS".
To reduce the playback voltage at 8kHz: Increase "BIAS".
Press the "play" button on the video recorder and hold it
down during the total adjustment process.
With the " – " or " + " button on the video recorder set the
±
output voltage to 0.5V 50mV. Whenever one of these
rms
buttons is pressed the voltage changes by 1dB and the set
value is stored in the EEPROM.
Terminate the Service Function by pressing button "standby".
Adjustment Procedure
The period is set with C2005
(CLOCK ADJ.)
±
0,715ns by the manufacturer.
Disconnect IC7101-(67), -(68) from +5V (Pin 33).
GV 411-2
to
(BIAS)
to 488.281,25ns
GRUNDIG Service