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dead modem? - psypher - 05-21-2020

Hi I got my wimodem232 a little while ago its version 2.1 but when i ordered it it didnt come with the lcd screen (which is fine not sure if it was not an option at the time). I have had it for about one month and it was working with no issue. I have a mac classic ii and im using it with zterm. yesterday i was connected to a bbs when suddenly while loading some text the text stopped and i got a circle character then nothing. it didnt say disconnected or anything just everything stopped in the terminal. so i power cycled the modem but nothing changed, i closed and opened the terminal program and it was as if it didnt see the modem anymore. i tried going though different baud rates with no success and eventually used the jumper to set the modem back to 300baud so i could be sure it was set right. that had no effect so i did a full reset (red blue flashing light) hooked it all back up and same thing terminal is just blank and cant do anything with it. I should mention that i let some time pass in between to make sure it wasnt just something strange . Is there anyway to test to see if it indeed is sending signals to the computer, i dont have another computer to test it with. all the lights seem okay plug it in and it goes white then yellow. any help would be greatly appreciated.

PS im in japan so i may not be able to respond right away.


RE: dead modem? - admin - 05-21-2020

It sounds like the WiModem232 is working (booting with the right colors, resetting, etc.).  The fact that terminal program just suddenly locked up makes me wonder if you had the SCC chip in your Mac go bad?

What you can do to try to test your computer is build a loop-back cable.  Basically, it ties TxD to RxD so every character you type in the terminal gets echo'd back to the terminal.  If this works, then the WiModem232 would be bad.

Make sure you are using a good 5v power supply for the WiModem232.  I saw odd things happen myself when powering it from a portable USB power supply where it's battery was almost dead.


RE: dead modem? - psypher - 05-21-2020

ill try the loop back cable any links to how to make one? the power supply is good and i have tried it with another just to make sure.


RE: dead modem? - admin - 05-21-2020

You need to determine the pinout of your serial port. I am not sure what exact Mac you are using. Have you tried a different terminal program? Maybe you have corrupted terminal software or a config file for it?

I offer a lifetime warranty on the electronics that I make, so I don't mind swapping this out with another one. It seems best right now to try to get the loopback test verified to make sure your Mac hardware is ok.


RE: dead modem? - psypher - 05-21-2020

i have a mac classic ii and im using zterm. i dont get anything in the terminal unless its connected to a modem so if i type in it nothing will show unless its already connected. so even after i made the loopback cable i dont get any information on screen. i did also try mac terminal but when i type there nothing will show up in the window however there is a (error) beep not sure if it would beep twice if it received data back as well. i tried that and only got one beep but again not sure if it would matter. is there any way to verify the scc chip is working?


RE: dead modem? - admin - 05-22-2020

The loopback test is how you verify the SCC! There is a program called "Snooper" for the Mac. It's a diagnostic program that I use to use with EMPLANT (the Mac emulation board I made for the Amiga). My board had real SCC ports and the loopback test would pass on it using Snooper. You could try to find that program (I am sure that Archive.org or some other place has it), and try that with your Mac. I am not sure what the Mac Classic II uses for the SCC. If it's the standard DIP package 85C30 then I happen to have hundreds of those chips still if you can't find one.


RE: dead modem? - admin - 05-22-2020

I looked into your Mac model. I can see that it has a SMT version of the 85C30. Sad That makes replacing it a nightmare. However, I did read that this motherboard does odd things (like no serial or AppleTalk) when there are bad caps. Do you have AppleTalk setup? That would be another way to verify the SCC is working or not.

Here is some info on the re-capping your Mac:

https://scruss.com/blog/2016/12/11/mac-classic-ii-rev-2-re-capping/


RE: dead modem? - psypher - 05-22-2020

(05-22-2020, 09:55 AM)admin Wrote: I looked into your Mac model.  I can see that it has a SMT version of the 85C30.  Sad  That makes replacing it a nightmare.  However, I did read that this motherboard does odd things (like no serial or AppleTalk) when there are bad caps.  Do you have AppleTalk setup?  That would be another way to verify the SCC is working or not.

Here is some info on the re-capping your Mac:

https://scruss.com/blog/2016/12/11/mac-classic-ii-rev-2-re-capping/
I dont have AppleTalk set up but im gonna try out Snooper tonight and let you know what I find. I also did a recap about two months ago so that shouldnt be an issue.


RE: dead modem? - psypher - 05-22-2020

(05-22-2020, 09:58 PM)psypher Wrote:
(05-22-2020, 09:55 AM)admin Wrote: I looked into your Mac model.  I can see that it has a SMT version of the 85C30.  Sad  That makes replacing it a nightmare.  However, I did read that this motherboard does odd things (like no serial or AppleTalk) when there are bad caps.  Do you have AppleTalk setup?  That would be another way to verify the SCC is working or not.

Here is some info on the re-capping your Mac:

https://scruss.com/blog/2016/12/11/mac-classic-ii-rev-2-re-capping/
I dont have AppleTalk set up but i just ran the snooper test and it didnt pass for modem or printer it said no hand shake and when it went though the baud rates it also cam back bad. what chip is it i have another parts board that maybe i will be able to get what i need from it. I also did a recap about two months ago so that shouldnt be an issue.

update I think its a AM85c80 which does the scsi and scc is it possible that only the scc would have failed? scsi stuff is still fine?


RE: dead modem? - admin - 05-23-2020

There are two chips that handle serial and SCSI. The 85C30 just does the serial. The 53C80 is the SCSI controller. It's funny that these two chips have these numbers, and they are often confused between each other.