Repair Procedure 13 - NCR PC4i Service Manual

Care should be used in removing any socketted IC
component or damage to the component/socket may
result.
CPU ERROR (8088)
Format of code:
CONTROL :01:00
Detail code:
NONE
Repair Procedure
Check the 8088 U6 (U125) for correct installation.
Determine if the ready line of U6 (U125) is active;
this will suspend operation of the microprocessor. If
this condition is observed then check RDY and DMA
wait inputs into the CPU VLSI (U7/125). If one of
these two control lines is not active then suspect
that the clock IC (U7) or the processor (U6)(U125) is
defective.
NOTE: A control line attached to a defective
that is also
gates can produce unpredictable results and
conditions that are difficult to troubleshoot.
INTERRUPT CONTROLLER (8259) TEST
Format of code:
CONTROL:02:ww
EXP DATA: xx,
LEVEL 1 DIAGNOSTICS ERHOB RETURNS
CAUTION
Date
13
attached to the inputs of other
Date
OBS DATA: yy
Time
Time
input
5-4?