MiTAC 7521 PLUS/N service manual 129

7521Plus / N N/B MAINTENANCE

8.11 SIO PORT TEST ERROR

An error occurs when a mouse or other I/O device is installed.

SIO TEST ERROR

1.Check if the mouse or others I/O device are installed (J507) properly.

(Including driver)

2.Check if CMOS COM port setting correctly.

Board-level

Troubleshooting for

SIO test error.

YES

Test

OK?

NO

Try another known good I/O device.

YES

Re-test

OK?

NO

Change M/B or go

into board-level Troubleshooting.

Correct

it and end.

Change the faulty part and end.

Check the following parts for cold solder or one of the following parts on the mother-board may be defective, use an oscilloscope to check the following signal or replace the parts one at a time and test after each replacement.

Parts:	Signals:
U27,U1	ISA_IRQ4	D/DCD#
Q1,R1	RS232_OFF#	COM1DCD#
	D/RI#	COM1DSR#
J507	D/DTR#	COM1RXD
	D/CTS#	COM1CTS#
	D/TXD	COM1RTS#
	D/RTS#	COM1TXD
	D/RXD	COM1DTR#
	D/DSR#

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