Check and Alianment
No alignment is needed for radio part. IC91 tuner is pre-aligned.
Dolby alianment:
cassette adjust
MTT 150
F = 400 Hz
200 nWb
3260
and
3261
AC voltage at pin
1
& 24 of 7251
= 387.5 mV +/- 50mV
Checks:
Reference oscillator frequencies
device MSM 6307
83CE558 HEF4521 SAA6579T
pin 24&25
51 & 52 4&6 13& 14
frequency 6 MHz 11.5 MHz 4.194304 MHz
4.332
MHz
0.5% 0.5% 20 ppm 60 ppm
FM mute:
98 MHzImV output at load resistor R & L = 775 mV = REF
no signal output should be < -24 dB ( REF - 24 dB )
Demodulated FM levels
Input Output of IC91 ( pin 16 & 17)
98 MHz 300 mV 50 mV .
IMPORTANT:
The search levels are measured and values are put in the EEprom at the factory.
Service provides EEproms containig mean values of search levels.
Consequence:
If you have to change the IC91 module, you must also change the EEprom.
7a
22DC594/35X
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