Is The Line Grounded? Y N; Defective Internal Cable; Defective External Cable; Defective Logic Board - IBM 5280 Manual

A
E
S
COMMUNICATIONS MAP
CBS COUPLER
PAGE 9 OF 13
066
- Disconnect the internal cable
from the A-ES-JOI connector.
- Use the CE meter on the RXl
scale to measure the resistance
to a ground pin. A short will
read less than 20 ohms. At the
POI connector ON THE INTERNAL
CABLE, measure from POl-06,
'Coupler Cut Through', to POI-23
,'Signal Ground' (MIM 867, probe
point E).
Is the line grounded?
Y N
067
Defective communications MPU
card(A-ES)(MIM 311).
If a 'Ros Patch' cable is
connected to the card,
GO TO MAP 0600, ENTRY POINT A.
0620
Disconnect
from the
J140.
the external cable
machine at connector
Use the CE meter on the RXI
scale to measure the resistance
to a ground pin. A short will
read less than 20 ohms. At the
P140 connector ON THE EXTERNAL
CABLE, measure from PI40-06,
'Coupler Cut Through',
P140-2l ,'Signal Ground'
867, probe point
F).
Is the line grounded?
Y N
069
Defective internal cable.
070
- Defective external cable.
to
( t'1IM
A A
B D
8 S
MAP 3012-9
071
- Defective logic board.
072
- Place the telephone(s) on hook.
Connect the CE meter leads TO
THE COUPLER as follows:
Minus to 'Signal Ground' (gray)
Plus to 'Data Modem Ready'
(yellow)
(ENTRY POINT B)
Again place a call from another
telephone to the coupler number.
When the coupler telephone
rings, take the telephone off
hook and observe the CE meter
for a +EIA level.
Does 'Data Modem Ready'
lead) go to +EIA level?
Y N
073
(yellow
Did the telephone stop ringing
when taken off hook?
Y N
074
Power off.
Remove the 3SLS card.
Check continuity between
A-D2oBIO '+Switch Hook' (MIM
867, probe point C) and the
Red lead AT THE COUPLER.
Is continuity good?
Y N
EC840874 PEC839787
1 1 1 1
2 0 0 0
A A A A
F G H
J
MAP 3012-9