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.
Macintosh 512k logic board problems
Posted by: jzyla on 2018-04-07 19:20:45
I am having issues with my Macintosh 512k.  The machine will usually boot with the checkerboard pattern shown in the pictures.  Sometimes it will make a very distorted sound on boot.  The issue is not with the crt as it has been tested with other boards.  Occasionally the checkerboard pattern will change. 

I suspect the the issue is with the roms installed.  I have tried cleaning the roms but this does not change the issue.  I am curious if any one else has ever had a problem similar to this.

8A2476C8-FE9F-4C79-B641-34C7F5C845D1.jpeg

5316E9DB-ED04-492A-8B52-64DA5CA81DFF.jpeg

433B41C6-4E62-4443-A7D5-F25D022A73F8.jpeg
Posted by: mactjaap on 2018-04-08 01:08:04
You can find all kind of “checkerboard” errors in:

Dead Mac Scrolls

https://ia801300.us.archive.org/1/items/mac_The_Dead_Mac_Scrolls_1992/The_Dead_Mac_Scrolls_1992.pdf
Posted by: jzyla on 2018-04-08 18:15:24
Thank-you for the response.  But the only solution in the dead mac scrolls for my scenario is the programmer switch being held down which is not the case.  Any other ideas?
Posted by: mactjaap on 2018-04-08 22:39:55
There are more checkerboard errors in the guide. Could be one of these.

But maybe someone of the forum recognize your error. That would be nice. 
Posted by: bibilit on 2018-04-08 23:19:09
in the second picture you can see a fault code and what's look like a distorted floppy image.

You probably have bad ram on this board, i will try new ones first.
1