Symmetricom 5071A, Сборка и сервисное обслуживание

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3. Theory of Operation
Functional Block Descriptions
144
Power Supply Block
All references to internal-battery power, battery status or battery
operation, do not apply for 5071A Option 048. Option 048 does not
have an internal standby battery.
The Power Supply Block consists of LF1 line filter/cable assembly, T1
toroidal power transformer, A1 rectifier/crowbar/Ext dc input filter circuits, A11
power steering logic assembly, A12 Dc-Dc power-converter module, and B1
24V internal standby batteries (Opt. 048 does not have batteries). This block
has three inputs and five outputs. Figure 3-3 is a power supply block diagram
that shows specific power paths to and from all power supply blocks with jack
and connector labels.
The power supply block provides the instrument with internal dc power from
either an ac power, internal standby battery (none for Opt. 048), or an
external dc power source. It monitors the presence of these power sources,
switching from ac-line, to external-dc, and then to internal standby batteries
respectively, (In opt. 048 switching is from external dc-line, to ac-line). In
addition, this block maintains the internal standby battery charge and protects
the batteries from catastrophic discharge, (none for Opt. 048).
AC power enters the instrument at LF1 line filter/cable assembly, providing
initial filtering, fuse protection, and line-voltage selection. The LF1 cable
assembly connects directly to the primary windings of T1 toroidal power
transformer stepping down the selected line voltage to an approximate 28
Vrms (37 Vrms for opt. 048) ac voltage. The T1 secondary output is rectified,
filtered, and crowbar protected by circuits on A1 producing a 32-38 Vdc ( 45-
51 Vdc for Opt. 048) voltage which is then routed to A11.
DC power enters the instrument at the rear panel EXT DC Input connector
(fuse protected by F2), is routed through low-pass filter components on A1,
and then sent to A11.
B1 provides 24 Vdc to A11 and receives an appropriate trickle or boost
charge input from A11 as required when ac power is applied only. (Does not
apply for Opt. 048).
A11 implements the power-source steering hierarchy, provides power-status
signals to A3, maintains the internal standby battery charge when ac power is
applied, and provides internal standby battery fuse protection (non-Opt. 048
instruments) . A11 receives the ac, dc, internal standby power sources,
selects one of them and routes it to the A12 Dc-Dc power converter module.
A12 converts the 22-42 Vdc ( 40-58Vdc for Opt. 048) steered power to
n5V, +12V, and -12V dc and routes these three voltages to A1 at
A1J2.
Note