Thanks y'all!
Just for info the steering was very random, i.e as you turned the wheel the police car would start to turn then go mental then car would appear flashing in 10 different directions at once, then you would hear the tyre screeching sound as if you were braking.
Almost like the steering optics had gone bad, but I had ruled this out ages ago by changing those for brand new ones from Farnell.
Needless to say you couldn't play the game like it.
What confused me is that this link:-
http://www.jrok.com/project/leta/
which goes on about the LETA chip saying that it's a 24 pin chip with the part no. part #137304-2002.
Well I changed that first and no change, that's what made me think "oh the LETA isn't the problem"
Then for sh*ts and giggles I swapped all socketed chips and roms from one good known working cpu board to the other, sure enough my fault carried across.
This proved the circuit board itself was ok and had no faults.
So yesterday one at a time I chip swapped, I ignored the main eproms and concentrated on the logic/ram/customs (whatever they are called you know I'm new to this) and when I got to the lower of the two 137304-1001 chips it cured the steering.
Am I right in guessing that the one above it controls the accelerator? Or is this present in case you run say Marble Madness as that would have more inputs??
Anyway, very happy I have a working set and enough spares to keep it going.
Also discovered that one of my very early APB sets which I thought had a bad board is actually ok, and it was broken power wires and bad filter board connectors which made me think that board was faulty when it wasn't, so I have a spare bottom board as well (APB video/game board)
I'm on a roll this weekend as my new Sega wonder boy (original) had developed a fault, the colours would go mad and flick orange, slowly this got more often, I saw IronGiant's/Vectorglow's repair log of my exact board and he said fixed colours by replacing IC9, which is now in a socket, I reseated IC9 and touch wood that seems ok now, these boards do flex and creak more than any other board I own, it's like it's too heavy for the thickness of the board, so maybe just because of each time I moved it, it was working that chip loose.
Happy for now! but after 37 bad chips it may have a few more yet, to me the MBM2148L-55's run ultra hot, is that normal? There is 6 together and they are all ultra hot after 3 mins of playing, anyway that will be another thread soon I'm sure!
Sorry for the blog.
. I'll also have a poke around for my Rampart boards to see if they made a LETA-less joystick version and a with-LETA trackball version.
