SE serial ports diagnostic and repair

[clh333]

I acquired an SE about a month ago - first one I have owned - and recently posted here a question concerning printing from the SE.  (I have a StyleWriter and couldn't make it work with the SE / OS 6.0. .

Since then I have been running tests on the machine and today ran Snooper 2.0, which diagnosed a problem with the serial port.  The first pass tested the modem port, which failed at all speeds tested, but skipped the printer port as Apple Talk was on.  I turned off Apple Talk and repeated the test:  This time both ports failed.

I understand there is a Zilog Z8530 chip which controls both ports.  I am assuming that is responsible for the problem.  But before I dig out the board I would like to ask whether any other diagnostic test could be run to confirm the problem.  Also, if anyone has a suggestion for how to approach the repair I would welcome their input.  For example are any other related chips suspect?

Thanks for your replies.

-CH-

 

[apm]

I don't know anything about Snooper, but usually the serial tests need a loopback cable installed (i.e. routing the transmit signal back to the receive). If you don't have anything like that attached, then I would expect it to fail.

 

[clh333]

Thanks for your reply. 

I eventually attached a known-good modem and tested with that.  Although the handshake test still failed the throughput tests passed.  I understand from reading that the handshaking is hardware-based; I don't know why that would fail but the modem cable is molded-on and so I don't know what I could do to substitute.

I also found an old ImageWriter II and was able to print to that through the printer port.  From these practical tests I concluded that the  Z8530 was working acceptably.

Thanks again for your help!

-CH-