The first big problem was relying on old schematics. I consulted 2 versions of nintendo clones and the original famicom. There were serious differences in the PPU pinout. Even though I did my best, I couldn't get the bus right the first time, and had to do a major repair.

(The machine on this picture is the MSX version of  Baffa-2. - ignore it :D )

Another problem is the fact that the original design used the BF494 transistor to oscillate the clock. It is very difficult to find a BF494 that works nowadays as many are rebranded or outside the original parameters. I made several purchases in different stores and tested several transistors from the BF494, BF494A series and I only managed to make it work when I took its brother BF495 and adapted it.

In practice, I found it best to use the 74LS04 to do the job, and it performed much better than the other tests.

The result is this:

Beautiful, isn't it?