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Macintosh SE/30 Recap Issues


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Hi,

 

I just completed recapping an old Macintosh SE/30 I got from a friend. Before the recap, the Macintosh could boot up, but hung at a somewhat distorted grey screen, with no mouse cursor and no startup chime. After the recap and upon first boot, I could hear the startup chime and the grey screen is crisp with no distortion. I thought I have done well when I realized that the machine would actually hang at the grey screen without proceeding to ask for boot disk (the internal floppy drive as well as the hard disk drive have been removed). There is no mouse cursor on the screen and pressing the interrupt switch would generate the chime of death. Pressing the reset switch will just cause a reboot, followed by the startup chime, and then the machine would freeze again.

 

I think that the machine hangs at the RAM test phase. With 8MB of RAM I could expect it to take at most 15-30 seconds to complete the RAM test, but I waited for 5 minutes and nothing happened. Most online sources describe similar symptoms (hang at grey screen, but with mouse cursor) and say that this has to do with the network filter at the serial port or the SCSI chip. Mine is different as there is no cursor. Regardless I have checked the connectivity near the SCSI chip and the network filter and all seems to be good.

 

The 30-pin RAM modules tested good on another machine so I do not think it is DRAM issues. 

 

Any ideas what else I can try? Many thanks.

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I have never tried to boot while the machine had no floppy drives plugged in, but I do know that the interrupt-crash thing is perfectly healthy. My SE/30 would get the "distorted" simasi screen, sometimes with a delayed chime of death, if anything major was wrong with the logic board. This is a dumb question, but have you tried plugging any drives in? Also, do the screen's corners get rounded off after a while?

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I have never tried to boot while the machine had no floppy drives plugged in, but I do know that the interrupt-crash thing is perfectly healthy. My SE/30 would get the "distorted" simasi screen, sometimes with a delayed chime of death, if anything major was wrong with the logic board. This is a dumb question, but have you tried plugging any drives in? Also, do the screen's corners get rounded off after a while?

 

Thanks for the fast reply!

 

When I first got the Mac, it came with an internal 800k floppy and a 40MB hard drive. Both were super noisy once power was applied so I removed them. Let me try plugging the SCSI2SD from Amigakit and see if it makes and different.

 

I did not notice if the screen corners get rounded after a while. Let me check. Does that indicate any issues with the analog board? During the recap I also checked the analog board and gave it a good cleanup. No obvious problems were detected, no capacitors seem to have leaked or bulged. The analog board was in fact quite clean so I did not recap that. 

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I got it working. Once I discovered some corrosions beneath the ROM slot, I washed the board a second time using white vinegar and let it dry for two days. Upon the next boot up, I immediately saw the familiar question mark on the screen asking for the boot disk! Yes, the motherboard, if working properly, is supposed to boot all the way until it asks for boot disk, even with no keyboard/mouse/floppy/hard drive attached. The machine now has System 7.1 installed using Amigakit SCSI2SD module, with the PDS ethernet card and everything (including file transferring via FTP) works perfectly fine. Audio is loud and great with no issues at all.

 

The only thing I regretted is that I slightly broke a plastic piece on 2 of the RAM sockets while swapping RAM, thinking that it might be RAM issue. Now that these 2 sockets are loose, I have to secure the RAM using tape instead. Good learning lesson for the next machine that I recap. There are still another three in the queue...

Edited by mdanh2002
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I think I also slightly broke one of my the arms on my SIMM slots, but it cracked diagonally so the RAM still stays put. I wonder how common this mistake is, by now; those things are brittle.

 

My RAM sockets were still pretty solid when I first touched the board. I think the sockets would have remain so had I been more careful in removing the RAM. Btw, the corners of the screen did get rounded off once the Mac found a boot disk and started to boot from it. The machine also comes with a SE/30 PDS Ethernet Card, which still works well. Unfortunately, download speed (tested with Fetch and MacTCP on System 7.1) is only around 30 KB/s at its best, despite the card being a 10Mbps card ...

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I bought myself an SMD rework station 3 months ago but so far only practiced to use it on an old VCR circuit board trying to remove some ICs. Did not get the results that I wanted and burned several nearby SMD components as well. So i guess using it on the SE/30 motherboard to replace the RAM socket is not for me. I am happy with using tape to secure the RAM - who's going to see it once the case is put back :)

 

During the repair process, I also checked through the commented ROM source code listing for the Macintosh Plus (not SE/30, but both should share similar ROM routines) here http://www.bigmessowires.com/mac-rom-inator/, it seems that the bootup routine starts with the check of timing signals, followed by the VIA and IWM. After that, the screen buffer is cleared and the RTC is tested by writing a byte and reading it back. If everything is OK at this point, then the 'bong' sound is played. After that, the RAM content is initialized, CPU type is checked (whether 68000 or 68010), and the typical grey screen boot screen is drawn. At this point, the boot disk icon is plotted and the machine starts to look for a boot disk.

In my case, the boot process hung after a loud bong and a crisp raster screen, with no disk icon. The machine only starts to look for a bootable disk drive after the disk icon is plotted, so one can say that the hangup was not due to external peripherals (e.g. issues with floppy or SCSI bus), but rather something that prevents the ROM source code from continuing to execute. This is what leads me to suspect ROM issues. 

To add on, the mouse cursor only appears once the machine starts to look for boot disk. As soon as it finds a boot disk, the mouse cursor disappears again, the smiley Mac icon appears and the corners of the screen become rounded (it was square right after the startup chime). By following these symptoms you will be able have some ideas where during the boot stage your recapped Mac hangs and isolate the issue.

 

@Boctor, yes, the boot chime is in the ROM as mentioned on the same website. I am not sure if the chime of death is also there too as I've found no mentions of it and have no time to dig into the ROM binary. However, I am still puzzled by the different screen patterns that show even when there is a problem reading the ROM. If the ROM is not functioning then which part of the board is actually responsible for drawing these patterns? Any thoughts?

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