Halcyon clone WIP - CPU, speech synth, keyboard, all working!

 Here's a video showing my progress on cloning the RDI Halcyon!

Halcyon replacement power supply finished

 Since I will need to return the original power supply soon, I needed to whip up a replacement one so I could keep working on Halcyon once I've returned the original.  Here's my quick n' dirty solution that seems to work.

Halcyon v2 repair log - RAM not working correctly

So I've got far enough with my Halcyon clone project to get the CPU working properly.  I wrote a small test program to test RAM I/O and also that the second EPROM (U32) can be read properly.  Right off the bat, my test program reported a RAM test failure.

After doing some digging, I isolated the problem to pin 20 of the RAM chip not having the proper timing.  This pin is driven by pin 8 of U18, as shown here:

A logic analyzer capture of a looping RAM read/write operation revealed the following on my clone PCB:

Pin 8 was starting and ending late.  You can compare this to the original Halcyon where pin 8 much more responsive:

Being utterly confused, I decided to hook up my scope to get a better view of the problem and saw this:

Finally, I looked again at the schematic and noticed that there is a capacitor attached to this line. Doh!

The problem ended up being that C39 needs to be a 0.001uF cap, not a 0.01uF cap.  Once I replaced the cap with the proper value, things started working.

Esh's Aurunmilla hardware is now open source!

I've sold all of my Esh's clones and commercial demand is exhausted.  So I've open sourced everything I created to make an Esh's PCB clone.  You can get it here: https://github.com/rulecity/EshsAurunmilla

Halcyon clone v2 repair log

•  Wrote test ROM, then hooked up logic analyzer to Z80 to see how far it got.  Was surprised to see that RESET' was held low.  Using logic probe, looked at U45 which is a flip flop that controls the reset circuit and saw that VRESET' was low despite WRESET' being high.  Hooked up logic analyzer to U45 and saw that pin 13 (flip flop reset) pulses low shortly after WRESET' goes high, which seems like it shouldn't be happening.
• Hooked up logic analyzer to U44 and saw that pin 8 (which is supposed to be an output) is mirroring pins 12 (an input that takes in a 4 MHz clock) and 11 (an output that takes the 4Mhz clock to the MC6803P microcontroller).  Pin 8 seems to be completely ignoring its inputs, pins 9 and 10.  The Halcyon uses a 74HC08 chip for U44 instead of a 74LS08 (which I am using for my prototype) so I'm going to try the 74HC08 to see if it makes a difference.
• Replacing U44 with 74HC08 fixed this problem!

v1 of Halcyon clone ready for testing

 It most likely has defects, but it's good enough for me to get some of these fabricated and start testing it.

COP421 reader finished!

 I finished building my COP421 reader and it seems to work perfectly.

I confirmed that the Halcyon COP421 program is identical to the dump that Mark Broadhead made over 20 years ago of the arcade Thayer's Quest COP421 program.

I uploaded everything (source code, CAD files, etc) to github, which you can find here: https://github.com/rulecity/COP421Reader/