Mitsubishi Electric DD-8020, Service Manual

Page: 14 / 68

Pickup (P.U.) transmission initial
operation does not occur.
The pickup transmission initial operation is carried out to
determine the initial position by transmitting the pickup to the
innermost position once (start-limit switch (pin 4 of CN503)
develops "L".) and to the external direction at low speed
(start-limit switch develops "H", turning off the switch.).
1
Does pulse of
1.65V 1.65V develop at
pin 162 of IC401?
Check BUS between IC401-IC306
and oscillation.
Check feed gear.
N
Y
2-1
"No disc" misjudgement display of
disc presence.
Does lens move with
UP/DOWN full stroke in
focus direction?
Is laser current normal?
Check IC401.
Does search signal
output at both edges of focus coil?
(Pins 15 to 18 of CN501)
Does focus search
voltage of 1.65V 0.4V develop
at pin 23 of IC503 (E544)?
Check pickup head
and wiring.
Does RFSB signal
develop more than 0.3V?
Check IC502.
Lens cleaning.
Replace pickup head.
Check peripheral
circuit of IC306.
Check IC503.
Y
Y
Y
Y
3
N
N
N
Y
N
N
Fig. 1-3-2
Fig. 1-3-3
1-8