Revox B225 Maintenance Instructions

R^OX
B225
SECTION 3/1
3. CIRCUIT DESCRIPTIONS
3.1 SERVO 1 PCB 1.769.310
The following circuits are implemented on the SERVO 1
PCB;
- Stabilization of the supply voltages
- Drawer position detector
- Focus control loop
- Disc motor control loop
3.1.1 Stabilization of the supply voltages
All supply voltages are stabilized by voltage controllers
(IC 4 to IC 9, LM317/LM337).
The +5V supply (+5 V STBY) is always available. It
supplies the microprocessor system and the IR receiver
even when the CD player is switched off (standby).
The remaining supply voltages are switched on or off
by the microprocessor with the PS-OFF signal. When
the CD player is switched off, PS-OFF becomes "H" (+5 V)
and transistors Q9 and Q10 become conductive
(staturated), causing the +5 V and +12 V supply voltages
to drop to a residual voltage of 1.3 V. The -7 V supply
is switched off through the circuit R38, R39
?
and Q8;
the -12 V supply via R52, R54, and Qll; and the -17 V
supply via R51, R53
f
and Q12. This prevents the positive
supply voltages from becoming negative. The voltage
is doubled through diodes D15, D16, D17 and capacitors
C29, C30
#
and taken to the voltage controller IC9 for
the -17 V supply. D18 protects the controller from
an excessive direct-axis component of the voltage.
3.1.2 Drawer position detector
The two light barriers DLQ1 and DLQ2 (on PCB 1.769.310)
check whether the drawer is open or closed. The
corresponding signals indicate the following conditions:

Revox B225 Specifications

General

Brand	Revox
Model	B225
Category	CD Player
Language	English