HP Integral Personal Computer Service Manual page 125

·8-42 Troubleshooting and Di ....... tlca
I ........ Penon •• Computer
nable 1-12. HP·IR Tro.bI .... ooting and Repair
Use the following procedure if a failure of the built-in HP-IB
is
indicated (by either the short HP-IB
test on the service ROM or the HP-IB test on the service diagnostic disc). In each of these steps,
always turn off the power before you connect or disconnect a cable or replace a component.
Not.: The following procedure applies only to the built-in HP-IB. For problems with an
external HP-IB interface, refer to the Integral Personal Computer Interface and Memory Mod-
ule Assembly-Level Service Manual.
Itep
1. Set up the computer to troubleshoot the
logic B peA (refer to table 8-27).
2.
Repeat the short HP-IB test on the service
ROM.
3. Run the continuous HP-IB test (on the ser-
vice ROM) by pressing (
SHIFT)
and the
HP-IB
test function key. (Press
(ESC)
to
stop.) Refer to the schematic in figure
12-9
while performing the following steps.
4. Probe pins 1 through 4, 9, 11, and 13
through 17 on the HP-IB back-panel con-
nector with a logic probe or OScilloscope.
Refer to
figure 8-8 for the pin aSSignments.
1 __
~
13
c a
D
a
HP-IB
D D
c
D
CONNECTOR
a
D
PINOUT
a a
D
a
c a
D
a
D
a
a
a
12 __ ~D
D-
~
24
I
Indicated Action
If the message
***
ERROR - 241
appears,
replace
U41
on the logic
B peA.
If the message
***
ERROR - The
HP-18
fa i 1 ed appears, go on to step
3.
Each pin should be toggling high
(+
2.7 to
+3.3Vdc) and then low
(0.0
to +0.3 Vdc). If
any of the outputs are not toggling high and
low, go on to step 5.
If all of the pins are toggling, the problem can-
not be traced to the component level. Replace
the logic B peA.
<l
1 2
3 4
J9
5
6
7 8
CONNECTOR
9
10
PINOUT
11
12
13 .14
15 16
11
18
19
20
21
22
23 24
......
25
26
Figure
.-8.
Connector Pin As.lgnments