Okay, fixing the problem with the MCM2114 RAM on the video board fixed both the programming and video display issues. Brilliant! So I have now run my first program and everything worked fine! I'm really looking forward to designing some bits now that everything's fixed. Interestingly, this must mean...

Okay, I found the problem. One of the RAM chips on the video board has a bad data bit. As the memory is 4-bit on an 8-bit bus I swapped two of the RAM chips around to absolutely make sure that the RAM chip was duff. I confirmed via the ascii table that bit-5 was the original problem, and when I swap...

Hi,

Thank you for the link. I have those diagrams, but it doesn't include schematics of the syntel board or video board. I shall start downloading component datasheets and get the logic analyser out.

Can't wait to get it working properly so that I can run a program on it!

Best Regards,

Brian.

Hi Guys, I have a problem with the display on my Orac. It looks like shift is pressed as it were. It's easier to describe in a photo: https://www.valvers.com/denford/orac/MyOrac/corrupt_display.jpg I was wondering if anyone has any pointers as to where to start looking. I don't have the schematics f...

Hi Guys, I finally tracked the stepper driver problem down to the 4516 IC on the half stepping board on the CD20 drive. So that problem is now solved. The spindle speed was easily solved by putting another motor controller I had lying around in, it works great and is hooked up to the spindle control...

Hi Guys, I have just acquired an Orac CNC lathe, which is in very good condition. I've fixed a limit switch problem, but the Z-Axis had troubles moving. It would sometimes drive correctly on fast speed, sometimes drive in the wrong direction on fast speed, and have very eratic behaviour on slow spee...