Quoted from slochar:
Nothing like doing stuff out of order! I do the same thing, and it gives me motivation to actually get the machine running.
Well, here's the changes you need to make to rom U6 to make the eject hole always start on the same value:
Comparing files cpu_u6.716 and ORG\CPU_U6.716
0000022E: 1E 13
0000022F: 34 0A
00000634: BD 00
00000635: 12 00
00000636: 74 00
00000637: 7E 00
00000638: 13 00
00000639: 0A 00
0000063A: ED 00
The number to the left of the colon is the offset into rom u6. The number directly to the right is the 'new' value, and the number all the way to the right is the original value.
what it's doing:
offset 22e is part of a jump instruction (originally jmp $130a, short delay), that occurs at the start of every ball after everything has been set up, ball launched etc.
the instruction changes to jmp $1e34, which is the first empty byte in the rom at the end.
offset 634 is location $1e34 once the rom loads, previously blank. Here's what the bytes do:
bd 12 74 jsr $1274 - this routine resets the counter for the top saucer and sets the light. This code is already present in the game, but normally only gets called when the value rolls over from 1-2-3-4-5 to 6, to reset it back to 1. Bally was well known in this era for using this type of counter, and since Stingray (and pinball, which uses the exact same rom) was ripped off directly from bally (not sure which game, but likely freedom), it does the same thing.
7e 13 0a jmp $130a - this instruction should look familiar, as it's the one that we replaced to get to this routine.
$ed - this is the rom checksum correction for the new routine that's been added.
Edit your u6 with your eprom burner software or something like frhed (a free hex editor), burn onto a new eprom (2716 or 2732 if you double up the rom/have your board jumpered differently) and every ball will start with whatever the default value is (it's not 55k!) - it's 5k and probably lights some other feature on the playfield, not sure what. The picture below is what pinmame debug looks like when testing/writing these mods....
[quoted image]
If you look at the full size picture, you can see some lit dots in a grid.... these represent lamps, solenoids, and switches.