Technics RS-TR474 Service Manual page 29

Microprocessor check section
Is the voltage at Microprocessor NO
pin 57 approx. 5V ?
Is the voltage at Microprocessor
pin 60 approx. 5V ?
Is the voltage at Microprocessor
pin 240V?
Is the voltage at Microprocessor
, pin 59 OV ?
Ne
YES
Is the clock oscillating ?
(check with an oscilloscope and
1:10 probe.)
Connection and power check.
NO
Are there pulses at
microprocessor pin 18 and CN3
pin 12?
NO
Check power, D601 and D602
circuits and their connections.
audio circuit
Does failure occur in audio
circuit or tape mechanism ? Te she-audlo-cireult
tape mechanism
To the tape mechanism.
Tape mechanism
DECK 2: iC701 @
Does the voltage input to AD
change as each operating switch
is pressed ?
NO
DECK 1:
Voltage increases from 0V
in approx. 0.4V
increments when Power,
Stop, F. Play, R. Play, FF
and REW buttons are
pressed in that order.
DECK 2: :
Voltage increases from
0.4V in approx. 0.4V
increments when Stop, F.
Play, and R. Play buttons
are pressed in that order.
Caution:
The counter reset is
connected to other
mechanism systems.
Example:
To check mechanism 1, be
sure to press the counter
reset switch on
mechanism 2.
Check continuity of switches
whose voitage does not change
when pressed.
In case of failure, replace with
new switches.
DECK 1: 1C701 @ or W701 © Q -
Tape mechanism 2 Tape mechanism 1
Does the voltage at
microprocessor pin 64 change
when S801 and S802 of the
mechanism PCB (or the leaf
switch of the mechanism) are
forced into the on positions ?
Does the voltage at
microprocessor pin 2 change
when S803 and $804 of the
mechanism PCB (or the CrO,
Metal switches of the
mechanism) are forced into t
on positions (A D1 D2) ?
YES
Connection check for Connector
switch failure.
Soldering checks
Do pulses develop at
microprocessor pins 25, 27-71
28 when the mode switch is
pressed on ?
Do pulses develop at
microprocessor pins 26, 27 and
28 when the mode switch is
pressed on ?
Microprocessor failure.
YES
Does the voltage at
microprocessor pin 1 change
when switch of the mechanis
(MODE, Revers REC INH and
HALF SW) are forced into the
positions.
Do similar pulses develop at CN1
pins 4, 5 and 6 of mechanism 1
when the mode switch is pressed
on ?
Connection checks for
connectors, FFC cable,
soldering, etc.
YES
Are pulses applied to termina
13, 15 and 16 of IC801 when t
mode switch is pressed on ?
YES
Are pulses applied to terminals
13, 15 and 16 of {C801 when the
mode switch is pressed on ?
mi Pattern and soldering checks.
- | Plunger failure.
Does the plunger instantly pull in | NO | Q803, Q804, D801, D806, D802,
Play button is pressed ?
D804 failure.
1C801 or IC802 failure.
Does the plunger remain pulled in
during FF/REW operations ? NO
YES |
Belt has come off.
Reel motor failure.
1C801 or IC802 failure.
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