+5V Standby Circuit; Troubleshooting +5V Standby Circuit; +12V Regulator; Troubleshooting +12V Regulator - Sony CPD-420GS Training Manual

+5V Standby Circuit

During 'Active Off' and 'Suspend/Standby' modes, the +8V DC secondary
supply applied to IC605/1 (INPUT1) and Q601/C is reduced to +5.5V DC.
In order to prevent loss of the +5V DC Standby, it is necessary to supply
a back up voltage.
During 'Active Off' mode, the +16V DC secondary supply source is re-
duced to +9V DC and is applied Q601/E. Q607 is OFF which turns Q606
and Q601 ON. Q601 then outputs +9V DC to provide power to IC605/1
(INPUT1). Finally, at the same time, IC605/7 (OUTPUT1) outputs regu-
lated +5V DC.
During normal operation, the +8V DC supply is used to provide VCC volt-
age to IC605/1. The "Back-up" supply circuit (Q601) is shut down via the
'REMOTE ON/OFF' command from IC1001/7.

Troubleshooting +5V Standby Circuit

The loss of the +5V DC Standby voltage may appear as a no power
symptom. Check the +16V DC source, R617, Q601, Q606, Q607,
IC605 and related components. Check the +8V DC source, D654,
R654 and D610.
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+12V Regulator

During 'Active Off' and 'Suspend/Standby" modes, the +16V DC supply is
reduced to +9V DC and is applied to IC605/2 (INPUT2). The 'REMOTE
ON/OFF' control signal from IC1001/7 is L and is routed to IC605/3 (DIS-
ABLE), which disables the +12V DC regulated output.
During 'Active On' modes, the +16V DC supply is applied to IC605/2 (IN-
PUT2). The 'REMOTE ON/OFF' control signal from IC1001/7 is H (+5V)
and is routed to IC605/3 (DISABLE) to enable the +12V DC output at pin
6 (OUTPUT2).

Troubleshooting +12V Regulator

During the 'Active On' mode, confirm the presence of +12V DC at IC605/
6 (OUTPUT2). If missing, verify that a H is present at IC605/3 (DIS-
ABLE).