HP Portable PLUS - Repairing the Modem

8-32 Troubleshooting
Portable PLUS Computer
Table 8-11. Repairing the Modem
Use this procedure if the diagnostic tests indicate a problem with the modem circuit. (This proce-
dure assumes that the serial interface operates properly.)
If you make a repair at any step, repeat the
modem test to see
if the circuit is repaired; if it's good, go back to the main diagnostic procedure in
section 8.2.1.
CAUTION
Don't replace resistors or capacitors on the original modem PCA or on a new modem PCA.
They have been selected at the factory to give transmission levels that meet FCC
requirements.
"'
01o\ON051 Ie
DIAGNOSTIC
[RROR
[RROR
I'IOO[I'I[N
GOOD
,
--
toIODEI'ION
GOOD
,
", P HIl
GOOD
Step
1. Note the outcome of the modem diagnostic
test.
2. Start the "Find Modem oscilloscope rou-
tine: To select this routine, select routines
from the main disc-based diagnostic menu,
then select the modem option.
3. Monitor the MODEMON signal while the
modem scope routine
is running: A3J2 pin
10.
?
?
?
I
§
AfGUIAfa
§
N:1aJ1OII'1l
N F>t:PI.. . cr
'''''''''IST;;w:I
Response
If failure code 216 or 314 occurred (or the
modem
is not installed), go to step 2.
If failure codes 216 or 314 were not indicated,
but any other modem problem occurred,
skip to
step 7.
If MODEMON is high while the circuit is "on"
this signal is good; go to step 4.
If MODEMON stays low, isolate the modem
from
A2U17 (PPU) by disconnecting, and check
the signal again
at A2U17, pin 33: if the signal
is still low, replace A2U17; if the signal goes
high, replace the modem
PCA.