I had a similar problem with an Indy I was rebuilding for a friend a while ago. The monitor would come on like there was a signal and just stay black, or go into suspend mode and then act like it had a signal and then go back to suspend. The problem turned out to be that the monitor just didn't support the combination of refresh and resolution, which is sad since the monitor was a brand new Sun one. After switching to an Ibm P202 it was fine. So it sounds like it just might be the monitor or the adapter.
WolfLord -
"Two Minus Three Equals Negative Fun" - Troy McClure
"Two Minus Three Equals Negative Fun" - Troy McClure