Jvc BR S422 E Service Manual Part 5

Page 36

7.4.3 Normal audio system

1. IC16, IC17 (LN/285M)
The LA7285M incorporates the LINE amp. REC amp, PB amp and the limiter circuit inside.

REC/ MUTE LINE] EP/LP Vac NIPPLE REC REC E0 REC LINE ALC
SE TUNER IS? FILTER AMP AMP Wit-3 AMP AMP DET
IPB OUT NFB KN OUT IN

HEAD 60 GND E0 50 E0 50 LINE ALC TUNER GND LINE
SW AMP SW-I $W-2 AMP AMP AMP FILTER IN IN
IN NFB OUT PB IN
Fig. 7-4-3 Block diagram
0 Pin functions
Pin No. Name Function
1 HEAD SW1 ON : EE and PB modes. OFF: REC modes
2 E0 AMP INPUT PB signal input from audio head
and
HEAD SW 2 ON : EE and REC modes, OFF : PB mode
3 GND Ground for exclusive use of head switch of pin (D. EQ amp. and PB EP switch
4 EP SW 1 Not used
5 EO SW 2 Not used
6 E0 AMP NFB To apply negative feedback for demonstrating equalizer characteristic
7 E0 AMP OUTPUT
8 LINE AMP PB INPUT PB signal input from E0 amp.
9 ALC FILTER Detection and setting of attack time and recovery time according to the time
constant of CR.
10 TUNER INPUT CH2 for input of time code signal (LTCl
11 GND Ground for circuits and blocks except head switch and E0 amp circuit
12 LINE INPUT EE. REC signal input
13 ALC DETECTION INPUT ALC level is determined by attenuation by R255. R256 (CH1) and R285, R286
(CH2).
14 LINE AMP OUTPUT
15 REC AMP INPUT Recording current is set by R254 (CH1) and R284 (CH2).
REC amp. is inversional amp.
16 LP SW Not used
17 REC AMP NFB To boost high frequency response depending on L, C, R connected.
18 REC AMP OUTPUT
19 RIPPLE FILTER
20 POWER SUPPLY (Vcc)
To remove ripple with capacitor
H M L
21 EP/LP/SP CONTROL EP LP SP
22 LINE TUNER PB CONTROL LINE TUNER PB
23 MUTE CONTROL MUTE - MUTE
ON OFF
24_ REC/EE CONTROL EE - REC
Table 7-4-1

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