ST700 GENERAL HANDBOOK
667/HB/27880/000 Page 80 Issue 8
Failure to isolate the supply before changing parts may result in damage to the
ST700.
6.4.2 General Requirements
When replacing PCBs the original PCB should be inspected and the following points
checked:
(a) Check the connectors on the PCB. Are any pins bent, broken or damaged in any
way? If there are, make a note of the PCB and pin number in the Controller Visit
Log Book as the ribbon backplanes may have been damaged.
(b) Check any ICs that are mounted in sockets and ensure that they are the correct
ones for the position and are securely fitted. Refer to the works specification for
further details.
A problem with a loose fitting IC or use of an incorrect one can usually be
rectified easily without having to fit a replacement PCB.
(c) Do not forget to record the replacement in the Controller Visit Log Book.
6.4.3 Access to PCBs in ST700 Cabinet Assembly
The ST700 CPU PCB is mounted directly on the outside of the ST700 Rack
Assembly hinged front plate and is easy to access once the Lid is removed from the
equipment mounting frame.
If a fault is suspected with the Phase Drive PCB, the whole Power/Phase assembly
is replaced as described in section 6.4.6.
If fitted, the I/O Board or OTU Board are fitted inside the ST700 Rack Assembly,
behind the CPU PCB.
Warning: To open the hinged plate, the 64-way Phase Control Ribbon cables at the
front of the ST700 Rack Assembly must be disconnected. Disconnection of the cable
disconnects all logic power from the CPU and therefore prevents the ST700
operating the lights, but it does not switch the incoming mains off. The mains
must be isolated at the master switch before any disconnection of cables or fuse
replacement takes place.
6.4.4 Access to PCBs in other Outercases
All ST700 Rack Assemblies installed in cabinets with 19” mounting kits provide full
access to the front face of the ST700 and have sufficient room to allow the hinged
front plate to swing open, giving access to the internal PCBs.
Access to the PCBs is the same as described in section 6.4.3.
