scrambled graphics on repro

eric.of.troy

Hey there everyone!



So I've had this issue twice so far, and haven't gotten around to attempting to fix it,  but ive had this issue twice thus far.



Once was with a Mario Adventure repro and the other was putting CA Raisins on a repropak.



I get scrambled graphics, but the games are playable (if you can deal with the terrible graphics lol).



My question is normally, what causes this?  I did read about someone saying replace the PRG rom earlier, but again, before I completely desolder it all again, I'd like to know a little bit about it since I hate desoldering.



With teh raisins game, I did neglect to put two extra capacitors there where it says inbetween the two EPROMs, not sure if thats an issue or not.  Other unrom tites I did with repropaks turned out fine, but I had some nice tiny 0.1 uf caps to pop in then.



Thanks in advance!

Lincoln

Depends on how scrambled things are.



For Mario if its complete noise your chr is not enabled. If its jumbled you had ve something else wrong.



For raisins check your mirroring

eric.of.troy

Mario was fixed. just had something connected incorrectly.



Raisins, the mirroring was correct, not sure whats wrong with it, ill just try reburning and seeing how that works.



Just to verify I did switch the mirroring and it got worse lol.

removed04092017

The mirroring should be wired to the mapper. Shouldn't be possible to switch it. But just post pics. And triple check your wiring.

eric.of.troy

I was using Brian's repropak for the raisins. So therefore I shouldnt have any issues regarding wiring =0) lol



Thats also how I switched the mirroring, since its just a solder jumper. (desolder the old, solder the new)



Im just guessing bad mapper chip or could something of went wrong with the ram? I have used chips from the same purchase on other ones with no issue.



I did make a temporarily socketed unrom cart so ill just give it another go lol.

removed04092017

Whoops, thought it was MMC1, it's UNROM I think. My bad. But still, the chips worked before, right? Did you put them in the right way?

eric.of.troy

Yea, I put em in the right way lol. And regarding the chips "working before", I never tested those specific ones. I was just stating that when I bought them, the other ones I bought with the ones i used for the raisins worked for other games. I bought about 15 of each of em (74hc32 and 74hc161, as well as the ram chips 62256, same brand) and theyve worked fine thus far so I wasnt suspecting them really. Granted, I could desolder em and tinker around with different chips and what not... but time is something never on my side lol.



Honestly, I'm probably gonna let it set around for a while; I was just tryin to get a feel for information regarding the scrambled graphics to see about how easy it would be to diagnose it and prepare a remedy. I'm a little too excited for makin some SNES repros since I got my adapter workin!



Thanks everyone for the input =0)

removed04092017

62256 should be 6264. 8KB CHR-RAM.



ETA: Seems you can use a 256, but just make sure it's set up and nothing is wrong with that setup.

eric.of.troy

Yea I did pick up some 6264 just recently to make sure that wasnt the issue too. I socketed the ram slot on the cart i mentioned earlier and ill report back on my findings heh. I've finally got more than my normal 1 day off per week, so I've got plenty of time this week!

eric.of.troy

Well, since I didnt feel like doing any desoldering yet, I just reburned it on a fresh eprom.



Not sure which of the chips were bad in the original, but i tested the fresh eprom with both 62256 and 6264 and both versions of the RAM worked.