IBM 5280 Manual page 228

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K
Q
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A COMMUNICATIONS MAP
R
1 CBS COUPLER
1
PAGE
12 OF 13
093
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 P140-20
'Data Modem Ready', to
P140-21 ,'Signal Ground'
(MIM 867, probe point F).
Is the line grounded?
Y N
094
- Defective internal cable.
095
- Defective external cable.
096
Defective logic board.
097
- Place the auto-call
the 38LS) in the
originate a normal
call.
GO TO PAGE 9, STEP 072,
ENTRY POINT B.
switch (on
position to
telephone
A
F
9
MAP 3012-12
098
Place the te1ephone(s) on hook.
Connect the CE meter leads TO
THE COUPLER as follows:
Minus to 'Signal Ground' (gray)
Plus to 'Off Hook' (blue)
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.
Is 'Off Hook'
+EIA level?
(blue lead) at a
Y N
1
3
A
S
099
- Check continuity between
A-D8B03 '+Off Hook' (MIM 867,
probe point C) and the Blue
lead ON THE COUPLER.
Is continuity good?
Y N
100
The
problem
cables.
101
is in
- Place
hook.
the telephone(s)
the
on
Go back to the MDI prompt,
answer 'Y', and follow the
prompts.
EC840874 PECS397S7
MAP 3012-12