Biege Desktop G3 and Viewsonic E771 No longer Working Together..Pls Help!

Hello. Please help me if you can. I still love my old G3 and use it for my SCSI scanner when I need to do scanning but over the years I have had to jiggle and prop up the Viewsonic VGA E771 monitor adapter to stay firm in the port in back because, more and more as time has gone by, the screen blacks out with an audible crackle as the green power light turns to amber, popping back on again as I re-position the plug.

As I said, this problem has gotten worse and worse over time, even though I rarely use the machine, and now.... completely not working. What's interesting is that, when the monitor's cord is NOT plugged into the adapter, the green power light of the monitor is on and the video display is working ("No Signal"). I have double-checked the dip switch settings on the adapter and they are correct... they have never changed in all these years so I know they are not the issue.

Is my adapter fried or my video card? How can I test this without another monitor? I do have an iBook and a MacBook Pro, one running Tiger, the other Leopard, whereas the G3 is still on OS 9.

Thanks for your input ahead of time.