A very long day of building.
Today the new panel board came in, so I assembled that and the fit was perfect. I also reinstalled the powersupply in the case, along with a slight modification to make it somewhat better accesible, using some connector blocks. Also some small parts were delivered so I could finish the mainboard as well. So I figured I might as well completely assemble the whole thing. Which meant wiring up the switch panel completely.
Once all the things were in place, hooked up, I decided to power it on and see what happens. I know the orignal ROMS are corrupt, so I wasn’t expecting anything. The lights came on (display did not) and a faint continous beep came from the speaker. No magic smoke anywhere, so that was certainly good. I tried various EPROMS I made, two diagnostics and one new copy of what supposed to be the original, but so far nothing happend other than the lights coming on. Which means time to diagnose the basics:
- Voltages are good from the powersupply, so test all voltages on all IC’s (5V)
- Is there a clock on the CPU? (Does the crystal give a nice steady beat?)
- Status of the reset line?
- there is probably a similar Backup Battery ON line like the Zyklus MPS which is enabled when the system is powered off. It should disable when powered on. This didn’t work properly on my Zyklus build, not setting the NMI on the Z80 low and I did rebuild that part on the mainboard, so that’s a likely candidate for some detailed research.
- if the CPU runs, then it’s time to start looking at data signals between the CPU and the duarts etc.
Another thing is to set up an emulator to test my diag roms. There are some ways to do this, which is something for another post.
Optically, she looks pretty good now with all the switches installed correctly and the fresh coat of paint.
This is the section of the mainboard I rebuilt. It was the only part of the board that had some moisture damagge, Also, the old batteries were removed.
Here’s how it was:
And the result:
