Hitachi HAM 70 Technical Information

Page 1

@HITACHI

SERVICE MANUAL

Technical Information

No. 302 E

HA-M7O

No. 288 EF HA-M7O
No. 297 EGF HA-M70

This Service Manual gives a description of the new circuits in the HA-M70 and so it should be used together with the
manual for the HA7M70 (Manual No. 288EF or 297EGF) which was recently distributed.

DESCRIPTION OF NEW CIRCUITS

This unit employs a microcomputer to select the func-
tions using the one-touch system (function control cira
cuit), perform muting and control the tape deck and
turntable. Fig. 1 shows a block diagram of the inside of
the microcomputer (HD38702 A10) and Fig. 2 shows a

block diagram of the unit itself.

Block diagram of inside of microcomputer (HD38702 A10)

\J

32: Mute output

REC indicator
output

316 Scan output (FF/HEW)

Pause output ii:

Stop output 2':

Play output 3|:

Turnt ble, deck

conlr

Start cut output 4|: 325 Scan output (STOP)
:3 Scan outputiPAUSE)
{323 Scan output(REC)

:Jzz PHONO

GND 5:
Record play
detection signal input 5E

Turntable operar 7:

Input identification

tion signal input E
Deck operation at: § :izl TAPE ,
signal input 3 Function
GND 9!: 'fi :im AUX outputs
:
Reset to: '3 :]l9 TUNER
VDD (+4Vi ll: .5 IIIB PHONO
Test i+ 14V) In: E :in TAPE Function
CE inputs
OSC 13: .331 ms AUX
gs
vss (+14V) NE .22 an TUNER _
Fig. 1
Table 1 List of HD 38702 A10 Functions
Pin no. Name Details

® m (S Deck control signal PAUSE, STOP, PLAY Signals are output at high level.

(9 Turntable control signal START/CUT signal is output at high level.

© Record play detection signal Low level signal is input when stylus descends onto turntable record,

(D Turntable operation signal Operational mode of turntable lS input, low level when turntable is operating, otherWise

(T/T signal) Signal is high level.

Deck operation signal Operational mode of deck is input; correspondence is made with scan outputs @N @ and
input is iudged when corresponding scan signal is high level Input is judged as "corresponr
ding Signal available when low level and as no corresponding Signal available" when high
level

®~ ® Function input signal Signal switched by function swnch is input, judged as "signal available when low level

@m ® Function output Signal Function Signal is output, Function which is selected by signal for indicator and input selecr

@ tor circuit is put in high level.

@N @ Scan signal Scan signal (or deck operation Signal acceptance is output. This is set to high level With
corresponding signal only and is swuched in succession (used together with pin. l.

® Mute signal Mute Signal is output at high level. Control signal of muting circuit for reducmg shock nOise
heard when turntable starts and when stylus descends onto surface of record. When ©
record play detection signal is input, function is released for about i second (signal is set to
low level).

SPECIFICATIONS AND PARTS ARE SUBJECT TO CHANGE FOR IMPROVEMENT.

STEREO AMPLIFIER

October 'I 98 1

TOYOKAWA WORKS