Hi Tony and welcome to JustAnswer,Thank you for the question and your patience. Should you still need assistance for information purposes only...Initially, would you consider an alternate approach? While waiting for a donor/replacement board, consider component level repairs.
A good number of issues with this model could be traced to low or missing voltages. Proposed preliminary tries then (if have not been done):
Do you have a copy of the Service Manual / schematic diagrams?
I understand Tony and unfortunately, this board is no longer readily available. I realize that this information may perhaps be not what was expected. Unfortunately, there is no quick-n-easy fix and neither is there a workaround; sorry for having to be the bearer of bad news.
Hopefully another member could provide an alternate approach to your concern. The question would be re-opened as I would opt out.
Still, good luck with the Denon.