Another board from Vamino this one a time pilot 84 with jerky scrolling but only in the vertical (to the top or bottom of the play area) direction.
Had no idea where to look but fortunately he also gave me another time pilot 84 boardset that was dead to help compare.
In attempting to fix the dead boardset (which now loops in the test pattern but never makes it to the rom/ram OK screen unless a put a known faulty 68A09 at the sub CPU position which lets it boot sometimes but without sprites) I was checking an LS86 at 14E with my logic probe and noticed the flickering matched the scrolling.
Checked the chip with slice and it was OK so moved onto the LS377 at 12D and that was OK too.
So moved onto the LS02 at 15F and the LS32 at 15G (which was a fujitsu) and the LS32 was bad.
Replaced and now silky smooth scrolling an all directions.
Had no idea where to look but fortunately he also gave me another time pilot 84 boardset that was dead to help compare.
In attempting to fix the dead boardset (which now loops in the test pattern but never makes it to the rom/ram OK screen unless a put a known faulty 68A09 at the sub CPU position which lets it boot sometimes but without sprites) I was checking an LS86 at 14E with my logic probe and noticed the flickering matched the scrolling.
Checked the chip with slice and it was OK so moved onto the LS377 at 12D and that was OK too.
So moved onto the LS02 at 15F and the LS32 at 15G (which was a fujitsu) and the LS32 was bad.
Replaced and now silky smooth scrolling an all directions.
