brain sore

[Jondav1120]

OK, So to recap...we now have a bootable HDD with the D8B OS on it, and that is now booting correctly? HDD, motherboard, graphics card, etc would all seem to be working as they should. Monitor is obviously working as the "dsp error - card not ready" appears on the monitor.
The problem now would appear to be a lack of communication between the cpu and the board. The boot process goes something like this:
1. On power up the Brain board and the DSP board within the desk boot up from EPROMs on each board and await communication with the CPU. Also the Brain board as part of its boot routine activates the Rude Solo light and displays the initial message on the VFD.
2. The CPU boots the D8B OS and at some point fairly early on in the process initiates communication over the data cable with both the brain board and the DSP board. Once communication is established the CPU downloads the actual operating program for the brain and DSP boards and then runs these.
As it stands the process is not getting beyond step 2. Both the "Error 43" on the VFD and the "DSP Error - Card not ready" on the monitor are symptoms of no serial communication between the main cpu and the processors on the brain and DSP boards.
There are actually two completely separate bi-directional serial interfaces carried over the data cable, one for the brain (provides all the control surface functions) and the other for the DSP (provides the audio control functions) and it would appear that neither of them are communicating properly. The apparent fact that neither appear to be communicating could possibly point to a faulty data cable, or it's plugged into the parallel port on the cpu (although I think from memory that this is impossible to do as one is male and the other is female).
I believe that you have already done this, but it would be worth double checking the serial port settings in the BIOS.
Might be time to open the console up and have a look at the power and serial data connections on the brain and DSP boards. Power is J41 on the Brain Board and J42 on the DSP Board. The serial port connections are J25 on the DSP Board and J26 on the Brain Board.
A quick check on the DSP Board would be to see if any of the three LEDs illuminate when the power is switched on. If they do then power is getting to the DSP Board. The three LEDs on the Brain Board are not so conclusive as there are four different power supply voltages going to that board +5, +12, and +/-16. If the LEDs illuminate on the brain board when power is switched on then the +5v supply is ok (which is the most important one for that board)