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| Mac Classic II Serial Port/Reboot Problem |
Posted by: dans1984 on 2019-06-18 12:02:37
Hi All,
I've had a Mac Classic II laying around for a few years and finally got round to recapping it as it had the screen bars. I thoroughly cleaned the board with Isopropanol put a new battery in it and it booted.
However, there is a couple of issues although one i think to be the original hard drive.
- It reboots 2 or 3 times on cold boot, chiming each time before staying on the screen with the floppy? icon (screen is a little wobbly, but that gets better after a few mins). After a few minutes i hear the hard drive spin up and then it loads and runs fine after that.
- I have connected the Mac to a PC using a Lindy Mac DIN8 to Serial DB9 cable and try and use Zterm and Putty to communicate, however the mac can only send not receive, I've tried pretty much all the settings. I'd eventually like to use it for transferring data/browsing BBSs.
If anyone has any ideas on either of these problems, it would be much appreciated.
Thanks!
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Posted by: Bolle on 2019-06-18 12:30:40
1. You need to recap the analog board/PSU as well on the Classic and Classic II. Caps on there are prone to failure.
2. I would start by checking if there are any bad traces in the serial section.
Grab the schematics and go testing your way from the SCC up to the serial ports themselves.
There are caps sitting right in the middle of the serial section between the receivers. The chance to have a broken trace somewhere around there is high.
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Posted by: dans1984 on 2019-06-18 12:54:38
Ah, I figured the analogue board might need capping as well.
Is there a good resource for Mac Classic II Schematics, anywhere i can download them?
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Posted by: Bolle on 2019-06-18 13:22:08
There is an archive of a lot of old Mac schematics on archive.org
Dont have the link right now on my mobile but you should be able to easily find it.
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Posted by: dans1984 on 2019-06-19 12:20:55
I've downloaded the schematic, checked every line, particularly the RxD lines and found all traces, as far as i can tell have continuity. I have checked the U3/U5 DS26LS32 and every pin is connected except U3 (Used for RxD) pin 9 should go to ground according to the schematic. However, it does not go to ground - visually it doesn't seem to go anywhere - so unsure if it should, there is certainly no evidence of damage or corrosion.
Any further suggestions?
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Posted by: dans1984 on 2019-07-06 01:05:02
Just an update, i've recapped the analogue board and the machine is working as new.
However, the serial issue still remains. I've tested as explained above but so far, not found anything particularly concerning on the board.
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