Control Data Corporation CYBER 180 810 Maintenance And Parts Manual page 73

CHANNEL DISABLE PARITY SWITCH
A channel disable parity switch software register is provided for each regular
I/O Channel. Its contents can be changed using the deadstart keyboard
maintenance command PS.
If the switch is ON, it forces a new parity of the data bits that are sent
from the external device and disables any parity error associated with the
data.
If the switch is OFF, it does not force a new parity and does not disable any
parity error. The parity sent to the PP is the same parity that is sent from
the external device.
POWER TROUBLESHOOTING
Ref er to the power down troubleshooting SAMS in appendix C if computer shuts
down on a fault condition. If more detailed infonnation is needed, refer to
the Power Distribution and Warning System manual.
The following two procedures are for use in checking the transformer and the
load in the bus-bar.
FAULTY TRANSFORMER CHECK
1. Press CABINET POWER OFF.
2. Disconnect all wires from all tenninals ·of suspect transfonner.
3. Using an ohnuneter, check for shorts between primary and secondary
tenninals. A good transfonner produces a reading of infinity.
4. Using an ohnuneter, check for open circuits across the primary and
secondary windings of the transfonner. A good transfonner produces a low
resistance reading across the windings.
SHORT IN LOAD CHECK
WARNING
Be sure no power is present when
making resistance measurements.
1. With an ohmmeter on Xl scale, check for a short between bus bar and ground.
2. If a short is detected, check for pieces of wire on other material that
may be causing a short in bus bar assembly.
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