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Best way to test serial ports on an SE/30

ironhalo

Active member
After several rounds of troubleshooting I have my external floppy and SCSI ports fully functional again. Now it’s time to focus on the serial ports.

What are the preferred ways of thoroughly testing these on an SE/30? Is it possible to cable them together and test them in a loopback configuration via some software utility? Or should I just dig out an old modem (and hope it still works) to send some AT commands to it via ZTerm? If the latter, would receiving AT replies from the modem prove the port is fully functional, or is more thorough testing of some kind required to come to that conclusion?

Thanks in advance!
 

Nixontheknight

Well-known member
for the modem port, test it using a modem, and type some AT commands, if you get back nothing or garbage (and you're sure you're at the right baud rate), it's bad, but if you get OK, it's good. As for the printer port, test it using AppleTalk, which would probably be a moot point if you don't have another mac with a printer port.
 

ironhalo

Active member
Yeah, don’t have another working Mac or printer here at the moment to test with, which is why I was hoping there might be a clever way to test one port with the other. Perhaps with a custom made serial cable and a diagnostic utility of some sort.
 

sstaylor

Well-known member
The old Apple service test software used what they called a "serial loopback cable" which you would plug one end into each serial port, but I couldn't tell you how it was wired. Perhaps it was just a plain null-modem cable but i honestly don't know.
 

ironhalo

Active member
The old Apple service test software used what they called a "serial loopback cable" which you would plug one end into each serial port, but I couldn't tell you how it was wired. Perhaps it was just a plain null-modem cable but i honestly don't know.
Yeah, that's exactly what I was imagining. Would have been silly for them not to have a procedure for that considering how easy it likely was to implement.

Is that Apple service test software for the SE/30 hardware something that is easy to find? I don't see anything like that on MacintoshRepository (searching "service" under the 68k category).

Is this it? https://www.macintoshrepository.org/104-apple-personal-diagnostics
 

sstaylor

Well-known member
I've been scratching my head trying to remember what Apple called the official testing software for repair providers. ServiceSource? AppleTest? It's been too long and my brain is in a cloud at the moment. I'll keep thinking and if I remember I'll let you know.
 

ironhalo

Active member
Cool, thank you. I'm intimately familiar with AST and ASD, as I managed an authorized Apple repair shop starting around 2005. However I'm completely in the dark on whatever software existed for service techs on the 68k platforms.
 
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craig1410

Well-known member
You might be thinking about MacTest SE/30 although I've not managed to get it working since it requires a SCSI loopback device as well as a serial loopback cable. What I've been using is Snooper which can test individual ports (modem or printer) by looping pins 1 to 2 and 3 to 5 inside the port. I just did this with the legs of an axial resistor chopped off. Pins 1 and 2 are the ones at the bottom and pins 3, 4 and 5 are the next layer up. No need to bridge 6, 7 or 8.

HTH - links below.

 
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