At The P140 - IBM 5280 Manual

D E F
2 2 2
COMMUNICATIONS MAP
CBS COUPLER
PAGE 3 OF 13
009
Defective communications MPU
card (A-E5)(MIM 811)~
If a 'Ros Patch' cable is
connected to the card,
GO TO HAP
uouu,
ENTRY POINT A.
010
Disconnect the external cable
from the machine at connector
J140.
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 P140-05 'Switch Hook', to
P140-21 ,'Signal Ground' (MIM
867, probe point
F).
Is the line grounded?
Y N
011
Defective internal cable.
012
Defective external cable.
013
- Defective logic board.
A B
2 2
MAP 3012-3
014
- Connect the CE meter leads TO
THE COUPLER as follows:
Plus to 'Signal Ground' (gray)
..... .! ___ . _ .L._ 9r-- •• ':.J..._'- l l _ ...... '
' - ' l l t y ; ; ,
\.U -..7 ........ ""''-'11 fl'-'''''''
- Take the telephone off hook.
- A positive deflection
indicates a -EIA level.
Does 'Switch Hook', (red lead),
go to a -EIA level?
Y N
015
Defective coupler or
talk/data mode switch.
016
The talk/data mode switch is
reversed in the telephone.
017
- Connect the CE
THE COUPLER as
met er 1 eads
follows:
TO
Minus to 'Signal Ground' (gray)
Plus to 'Switch Hook' (red)
- Take the telephone off hook.
- A positive deflection indicates
a +EIA level.
Does 'Switch Hook', (red lead), go
to a +EIA level?
Y N
018
4
G
The talk/data mode switch is
not wired to the coupler.
Have the customer place a call
to the telephone company.
EC840874 PECS39787
MAP 3012-3