This was a fun one. I have a whole box of these boardsets and I figured out which ones had working CPU boards, so I was able to immediately narrow it down to the video board. The initial problem with this board was that the board was doing nothing, just displaying a blue screen.
Just randomly probing around randomly at the buffers going between the video board and the ribbon cables going to the CPU board. The overall goal was just to make sure that the two boards were talking to each other. I stumbled across H1, a 74ls245. The outputs looked really odd so I decided to just replace it. After replacing it, I was able to see the game! The only problem here was that it was missing ALL moving objects (Notice the guy doing the acrobatics is missing).
The way hypersports works, is that there are two main sections in which graphics are generated (ignoring the parts that generate clocks and whatnot): Background graphics and moving objects. Down the line they are mixed together to create one full image. With this one, since it was just moving objects, I figured that it was either the data getting lost on the way to the mixing, the ROM/RAM is not getting activated, or there was a selection problem when mixing the graphics.
The first thing I did was double check the ROMs were being activated and sending data out. With that verified, I double checked that the Konami 083 custom was outputting data to the color PROM. From there it was checking to see if the color PROM was talking, it was so data was at least making it out. This meant that there should at least have been SOMETHING on screen, so the problem had to be with the mixing together.
Probing around with the enable and select lines of all the multiplexors and the buffers I noticed that the signals 512 and 5̅1̅2̅ were always stuck low and high respectively. That is super odd as this is clock signal used for selecting these. Tracing it back I ended up at B4, which was a 74ls74, a dual flip flop. Looking at the signals, it was getting acting as it was supposed to, but the problem was that it wasn't getting a valid data input. Moving to the next part of that flip flop, I noticed that it wasn't getting a clock, which is not correct here. I traced it back to B3, which takes the 1H and 4H signals and makes a clock out of them. It is always activated so it should be doing something as long as the inputs are valid. Both 1H and 4H were toggling appropriately (they really should have been if I was getting anything on the screen at all as these are timing for video), but there was no output. This was our culprit. After replacing it, we got our objects back!
After closely looking at the graphics, this board was all set.