Recent content by Builde68

Hi Chris, welcome to the hobby! First off, I’d recommend grabbing a good set of schematics for the Macintosh 128K/512K. They are widely available online and will be your best friend for this project. Looking at your pictures, that motherboard doesn't actually seem to match the first revision...

The screen pattern is unusual for a Macintosh Plus. Let's hope the problem isn't in the glue logic, as that is complicated to diagnose. The 74253s and 74257s are the prime suspects; they multiplex the address lines for the RAM for both the screen display hardware and the CPU. To me, it looks...

That distorted sound reveals something isn't being read correctly. If the chime is the right length but the wrong frequency or texture, it suggests the CPU is executing the startup code, but the data being fed to the sound buffer is corrupted. Replacing those original single-wipe sockets with...

By any chance, is it possible to you to publish a picture of the back of this Mercury board that is as good as this one?. Many thanks in advance!

The problem is not on the Performer board's side. You should try to boot the Plus with a PicoPSU or an ATX PSU to discard issues related to the analog board itself. Also, the symptoms you describe are quite frequent due to poor connections caused by micro-cracks in the solder joints of the power...

Had a very similar issue with my modded version of this Performer accelerator for the Macintosh 512ke (It has a SCSI interface and 128K ROMs, along with a RAM expansion board of 4MB, so practically it is a Mac Plus). The Performer 2.2.1 extension makes the machine freeze right after the welcome...