PB 2400c + StyleWriter 2200 = serial connection issues

[jonpurdy]

So this is a weird issue that's taken me many months to diagnose.

• Picked up PowerBook 2400c from @JRL in February and it works really well aside from this issue; absolutely my favourite Mac ever despite the tiny keyboard.
  
• Ordered a StyleWriter 2200 shortly after that in almost mint condition from Japan, finally received it in late May.
  
• SW2200 boots up, prints test page just fine, paper occasionally jams but it does work. Except that it doesn't receive print jobs from the PB2400 (2400 just says it couldn't communicate with the printer).
  
• Recapped SW2200, same issue.
  
• Ordered a second (cheap) SW2200 around July; same issue. Works fine with test printing but PB2400 can't print to it.
  
• Checked the miniDIN 8-pin cable and each pin has continuity.
  
• PB2400 has the correct extensions (tried both the original 2200 and later 2500 extensions). Tried 7.6.1 and 8.1.
  
• Got lucky and found a DB9 Serial Port Plug (Apple #077-8129) to run the MacTest Pro serial loopback; failed! 
  
• Ordered a second logic board and IO board for PB2400. All combinations of original + second boards don't print to either printer and fail the serial loopback test.
  
• However, randomly figured I could the PB2400 into my MBP using my USB-Serial adaptor and the mini-DIN to DB9 cable. Tried this and I was able to send text across the wire with ZTerm! Major breakthrough! (Even tried this out with SheepShaver and pointing the modem port to my USB serial device and it works great!)
  
• Edit: when I try to print with PB2400 connected through USB-serial on MBP listening in CoolTerm, I do see a few hex characters show up, so the 2400 is definitely trying to do something.
  

To summarize:

• PB2400 (original parts) + SW-2200 A = can't print
  
• PB2400 (original parts) + SW-2200 B = can't print
  
• PB2400 (newer parts) + SW-2200 A = can't print
  
• PB2400 (newer parts) + SW-2200 B = can't print
  
• PB2400 (original parts) + serial loopback test = fail
  
• PB2400 (newer parts) + serial loopback test = fail
  
• PB2400 (newer parts) + ZTerm to MBP = success
  
• (didn't test original parts + ZTerm yet)
  

So, are there any ideas about what to try next? It is possible that both SW2200s have the same issue (they test print but can't receive data from the Mac). I don't have a second vintage Mac here to test and won't be buying one (no space and have enough machines back in Toronto). But I'm happy to have spares of everything; I would've ordered these even if I didn't have this issue.

 

[cheesestraws]

Perhaps a silly elementary suggestion, but: have you checked that AppleTalk is not trying to use the serial port?

 

[jonpurdy]

Perhaps a silly elementary suggestion, but: have you checked that AppleTalk is not trying to use the serial port?

Ah yes, I should've mentioned that. AppleTalk is always disabled, and I've even tried booting with extensions disabled except the ones related to printing just to make sure there's nothing else trying to use the port.

 

[vacputer]

I just gave this a go and I couldn't replicate the issue. What version of the SW2200 driver are you running?

 

[jonpurdy]

I just gave this a go and I couldn't replicate the issue. What version of the SW2200 driver are you running?

Funny enough, this did not end up being the problem.

Long story short: I randomly ordered a vintage Apple serial cable (with the actual Apple logo on the ends), figuring that it had a 5% chance of fixing the issue. Remember, I tested continuity of each of the pins on my first cable and it worked to send data over ZTerm.

Of course, I plugged it in and it worked perfectly. No issues printing at all, and it worked on both printers flawlessly. So after all that, it ended up being a weird cable. I regret nothing because I love having spares for the printer and the 2400c, though it would've been nice to be able to print for the past few months.

Now the big question: why wouldn't the cable work? I'm not an electrical engineer but could it have something to do with the resistance and maybe the printer or 2400c weren't sending a clean enough signal, or something like that? 

 

[cheesestraws]

Now the big question: why wouldn't the cable work? I'm not an electrical engineer but could it have something to do with the resistance and maybe the printer or 2400c weren't sending a clean enough signal, or something like that? 

Does one of them have the TX-RX pins crossed over and one not?  That would account for the original working to the mbp with a terminal program but not to a printer...

 

[jonpurdy]

Does one of them have the TX-RX pins crossed over and one not?  That would account for the original working to the mbp with a terminal program but not to a printer...

It’s possible I suppose. I am a bit ham-fisted and might’ve checked continuity incorrectly. I’ll check again out of curiosity.