Dark Corner in Images - Minolta A1

[CWH]

I recently noticed that in the upper right hand corner of my pictures there is a blacked out area. It effects the upper most corner and the shape of this black out area is in the shape triangle with a curved bottom. The area affected by this blacked out area changes with zoom changes. This blacked out area is also visible on both the LED screen and eye view as well. Its size changes but it’s no larger the 1/2 to 1/4, but it is noticeable. I have attached two images that shows this problem, any thoughts as to what might be causing this? My question is have you seen this problem before and is it repairable? Any assistance in this matter would be greatly appreciated.