Step 5 Device Adapters - Driver/Receiver - IBM 3274 51C Maintenance Information

Step 5 - Device Adapters - Driver/Receiver
a. Category A Device Failure (one or all devices fail)
(1)
(2)
(3)
Replace the type A tenninal adapter card No. 12
and driver/receiver card No. 28 (located in the
coaxial panel).
Reseat device A cable AI-Zl or Z3.
If this is a new installation, a missing Device Ready
o
or a missing Downstream Load
D
on a 3290
(in the Operator Information Area) may be caused
by customization response 112, 116, or 117
(number .of terminals attached).
(4) One device fails - go to step c.
b. Category B Device Failure (one or all devices fail)
(1) Replace the type B terminal adapter card Nos. 24,
25, 26, and 27, and driver/receiver card No. 30.
(2) Reseat device B cable AI-Z2.
(3) All devices still fail. This could be caused by one
disabled Category B device. Perform step d (Device
Summary Status, Test 3); if line 2 (status of each
display) indicates one dash (-), isolate problem to
that 3277 device.
(4) One device fails - go to step c.
c. Device Problem Isolation - Category A or B Devices
(1) To determine the failing 3274 port location,
perform step e (Device Summary Status, Test 3), or
see the customer's Device Cable Attachment Form
to convert the failing network address (device) to
the actual coaxial port location.
(2) Check the coaxial cable device for defects. Cables
to the same type of device can be interchanged
(3278 for 3278, 3287 for 3287, etc.) to assist in
problem isolation. The coaxial port panel is shown
below.
Al-Z2
Al-Z3
• • • •
Type B
Ports (4)
o
•
4
•
3
2 3
B
• •
5 6
A
• •
2
•
7
_____ Type A
• Ports (8)
o
Coaxial Panel, Port Layout
(3) Check the internal device A and B cables for
defects, using Figure C-13 for A devices and Figure
C-18 for B devices.
2-8
d. Isolation Procedure for a Coax Problem
I
If possible, exchange the suspected coaxial cable with
the cable at a known working port location. A device
POR is required, after the cables are interchanged, for
the control unit to recognize the change. For
~
display,
set the Normal/Test switch to Test, then back to
Nonnal. (However, on a 3290 display, turn power off,
then on, and wait up to 2 minutes.) To isolate a failing
display coaxial cable, verify that the Ready
0
symbol,
or
D
symbol for a 3290, is displayed.
Warning: When device cables are being exchanged and
the devices are different or the screen size or features are
not the same, addressing problems may occur which can
affect system operation.
Retry the failing operation or run the Test 0 display
pattern. To run Test 0, see 3274 Models 51C, 52C, alld
61C Maintenance Concepts, SY27-2528.
Notes:
1. Perform Step 5, d( 1) and d(2) to isolate a cable
problem.
2. It is possible to have unassigned Type-A ports if port
addresses were individually configured. Run the /3
test, and check for x in line 2. See Step 5, item e,
Example C
(1) Resistance Test (to attached device). See Figure
2- 6
8.
Note: The coax signal and shield are transfonner-
coupled at the device driver/receiver. Resistance
test applies to Category A terminals only.
Power does not have to be turned off on either
the 3274 or the attached device.
Disconnect the cable from the 3274 coax panel.
Measure the resistance from the center pin of the
connector, on the cable end, to the outer case of
the connector. Use the R x 1· range on the
meter. The presence of 3274 driver/receiver
signals will not affect the test.
Is the resistance between 1 and 250 ohms?
N
• If the resistance is too high or
infinite, check for an open or a
faulty connection.
• If the resistance is zero, check for
a signal-to-shield short.
Reconnect the cable at the 3274 coax panel.
Power does not have to be turned off at the 3274.
(2) Resistance Test (To 3274). See Figure 2-6,
O.
Disconnect the coaxial cable from the attached
device. Measure the cable resistance again, but at
the device cable end, using the R x 100 range on
the meter. ..
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