My Scramble is... well... scrambled

Are the voltages okay?

If so then it looks like a logic fault, ie probably a dodgy IC. I can't say which one as I haven't repaired a Scramble for ages, but it should be easy enough for a US-based repairer to sort out (I'd offer but I'm in the UK) - Channelmanic readily springs to mind:

http://forums.arcade-museum.com/member.php?u=38653
 
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I'd start by checking the 2716 ROMs at 5H and 5F. Pull and verify them, and then check for stuck/shorted/open address and data bits. Then maybe the 2114 RAM at 3M and 3L.
 
I'd start by checking the 2716 ROMs at 5H and 5F. Pull and verify them, and then check for stuck/shorted/open address and data bits. Then maybe the 2114 RAM at 3M and 3L.

Be sure to look down into the sockets too. I had a sound failure on my Gauntlet and reseated the ROM to no avail. Pulled it a second time and noticed corrosion in the socket.
 
I'd start by checking the 2716 ROMs at 5H and 5F. Pull and verify them, and then check for stuck/shorted/open address and data bits. Then maybe the 2114 RAM at 3M and 3L.

Just tried swapping 3M & 3L and that didn't change the problem, so unless they're both bad (unlikely) I'm going to assume they're ok and move on to checking out the EPROMs mentioned.
 
There seems to an alignment problem with the layers if that hints at anything, I noticed on the enemy list screen the yellow on the enemie's main base if shifted to one side from the rest of the colors.
 
Just curious if you made any progress on this. Have you logic probed the ICs feeding into and out of the graphics ROMs and RAM? e.g. buffers and muxes
 
Just curious if you made any progress on this. Have you logic probed the ICs feeding into and out of the graphics ROMs and RAM? e.g. buffers and muxes

I've poked around a little with a logic probe but I'm a serious newb and I'm not sure what to be looking for, so it's going to be an educational experience if I figure it out.
 
Could be a bunch of things. Are the sprites flickering? If both the sprites and the background flicker / behave erratic, I'd check the 7- and 8J (adders), which are used to determine sprite intersect and scrolling.

If sprites are okay and it's just the background, I'd suspect either the RAM's at 3M / 3L or anything that surrounded them ( latch, mux, etc ). That section is located pretty much in the center of the schematic.

Hard to go on just a picture but it's something to go on I suppose :)

-Y
 
Could be a bunch of things. Are the sprites flickering? If both the sprites and the background flicker / behave erratic, I'd check the 7- and 8J (adders), which are used to determine sprite intersect and scrolling.

If sprites are okay and it's just the background, I'd suspect either the RAM's at 3M / 3L or anything that surrounded them ( latch, mux, etc ). That section is located pretty much in the center of the schematic.

Hard to go on just a picture but it's something to go on I suppose :)

-Y

I'll try to take some video when I get home, I've got a cheapo flash card cam so it shouldn't be tough and I'll stick it on Youtube.
 
Sprites seem to work fine so I'm (cautiously) ruling out the adders. Both sprite- and scroll positions go through the top part of the schematic. Adders 7- and 8J are responsible for detecting the intersection between a scanline and a sprite but is also used to offset the columns, which are messed up on yours. Since it *looks* like the sprites are behaving normally, I'm thinking that HPLA0-7 are wrong for the background, which could either be a bad ram (3K/3J or 3M/3L) but could also be because it's addressed wrong by the multiplexers (74157's) in-between ( 6N, 4L/M or 6P)

Again, not much to go on without actually checking it hands-on...

Keep us posted and good luck!

-Y
 
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