68kMLA Classic Interface

This is a version of the 68kMLA forums for viewing on your favorite old mac. Visitors on modern platforms may prefer the main site.

Click here to select a new forum.
Memory expansion on Macintosh Classic
Posted by: plb007 on 2020-10-17 20:40:45
Hi, 

I just recap a Macintosh Classic I bought (didn't try before recapping)

The motherboard is in good condition before (and after) recapping. 

When memory expansion module is installed, I got a 00000005 sad mac error code. Without the expansion module, the unit boot fine (but can't finish the boot because system 7 needs more ram) . I tried swapping with a known working module without any luck. 

So, I guess the problem must be located on the motherboard. 

Where can I look first ?

Thanks,
Posted by: Garrett on 2020-10-17 21:54:14
Did you make sure the jumper was configured properly? There's a jumper for selecting whether additional SIMMs are installed or not on the expansion board.
Posted by: plb007 on 2020-10-17 21:55:49
Hi, 

Yes, i tried with additional RAM (with properly configured jumper) and without (switching the jumper) with no chance to get it boot. 
Posted by: rplacd on 2020-10-17 23:37:16
Huh, strangely enough I'm having a similar but not identical problem – recapped my Classic's AB (save for the really large power filter caps), have a known good LB. When the memory expansion is inserted, I get a blank screen (as if someone had removed the ROM), and then over time garbage on the screen. I wonder if the problem's really with the AB? I'll be checking to see whether I've installed the caps right on mine, checking voltages, etc.
Posted by: warmech on 2020-10-18 01:43:18
Second on checking voltages; I'm guessing you tried the original "faulty" expansion card in another Classic as well? I suppose it is entirely possible that the original card is indeed bad, but you also very likely have another underlying issue on the logic board or analog board.

But yeah, check the voltages; low voltages can cause all kinds of weird boot issues. I ran into all kinds of funky behavior with my (now dead) Classic II; come to find out, the +5v rail was too low for the logic board to work consistently.
Posted by: Juror22 on 2020-10-18 04:13:03
I found that mine was really picky about the RAM used and I went through several sticks that did not work or sort-of worked and gave symptoms, similar to the ones that were noted above.  I too questioned whether or not there was an issue with the expansion card, until I found the right ones.  I don't have any good examples of what doesn't work (I didn't keep track), but to finally upgrade mine, I used known, working, 1MB SIMMs that I pulled from an SE/30.  Oh, and from the apple documentation, you cannot use 2 chip SIMMs.  My MB has been recapped, as well.
1