Tandgnissle
Student
So I thought I'd post a work in progress on Capcom's F-1 Dream that I bought with a known sprite issue.
It's having this lovely issue:
As you see the two lowest sprite lines are shifted 16 lines up and displacing those a further 16 lines up.
Since the graphics are not really corrupted there is nothing wrong with the roms but I validated them either way and they were OK.
I reasoned that's it's probably an address error some where since the data is OK and it's two lines on two 8 bit
At least the sprite roms helped me start poking around in the right area, it's quite a large assortment of logic on this thing and not one Fujitsu to blame.
I found one suspicious thing that turned out to just be a bodge, there were at least five bodges I found on the boards.
Without the bodge the game just displayed a pure white screen. I put a piece of a resistor leg there to not confuse me in the future.
I also came across this and thought aha!
Well scope showed activity there so it was working I replaced it either way, put it in a socket for good measure and touched up a few vias around that area that looked like the solder had some corrosion on it. Thankfully it was only a very small area that mild corrosion on it.
Of course that didn't fix the problem. Due to me not finding any schematics and tube in my scope having seemingly broken (My poor 100MHz four channel Tektronix 2245A) While waiting for the logic probe to arrive I've started mapping out the address lines going from the sprite ram (which I did check with the scope while it was working).
It might be overkill, stupid and inefficient but at least I'm learning and I'll have an easier time one the logic probe finally arrives.
If you do have any idea though I'll happily skip this tedious part of the diagnostics.
It's having this lovely issue:
As you see the two lowest sprite lines are shifted 16 lines up and displacing those a further 16 lines up.
Since the graphics are not really corrupted there is nothing wrong with the roms but I validated them either way and they were OK.
I reasoned that's it's probably an address error some where since the data is OK and it's two lines on two 8 bit
At least the sprite roms helped me start poking around in the right area, it's quite a large assortment of logic on this thing and not one Fujitsu to blame.
I found one suspicious thing that turned out to just be a bodge, there were at least five bodges I found on the boards.
Without the bodge the game just displayed a pure white screen. I put a piece of a resistor leg there to not confuse me in the future.
I also came across this and thought aha!
Well scope showed activity there so it was working I replaced it either way, put it in a socket for good measure and touched up a few vias around that area that looked like the solder had some corrosion on it. Thankfully it was only a very small area that mild corrosion on it.
Of course that didn't fix the problem. Due to me not finding any schematics and tube in my scope having seemingly broken (My poor 100MHz four channel Tektronix 2245A) While waiting for the logic probe to arrive I've started mapping out the address lines going from the sprite ram (which I did check with the scope while it was working).
It might be overkill, stupid and inefficient but at least I'm learning and I'll have an easier time one the logic probe finally arrives.
If you do have any idea though I'll happily skip this tedious part of the diagnostics.
