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PostPosted: Wed Sep 12, 2018 6:47 am 
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Joined: Tue Feb 14, 2017 9:50 am
Posts: 89
I just obtained a Super Fighter II mini famiclone which is, as its name suggests, a small NoAC clone. Main board reads UM6561B. Overall it works (the power board quality is quite dubious, some solder point rusted and detached from the board, so I rewired them).
There's two issues, the video is very noisy (especially on the capture card) and it is having some serious problems with the triangle channel.

SMB2j, Gimmick and some multicart
Micro Machines title On this one the problem is really apparent. There's also some very odd noises which come up with Gimmick notably (but also some other games not using expansion audio).

What could be the cause? (Also, could this be converted to NTSC?)


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PostPosted: Wed Sep 12, 2018 10:54 am 
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Joined: Sun Apr 13, 2008 11:12 am
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Location: Seattle
MLX wrote:
the power board quality is quite dubious, some solder point rusted and detached from the board, so I rewired them).
There's two issues, the video is very noisy (especially on the capture card)
Looks like the power supply is lousy enough that it's coupling into the crystal driver, and it's got some noticeable jitter. I'd try using an external higher-quality 5V supply for testing.

Quote:
having some serious problems with the triangle channel.
Listening to Micro Machines,
- The pitches are correct
- The duration is wrong (sometimes notes are entirely missing) and there's this weird garbling

I think there's something wrong in the die? Probably irreparable.

Quote:
Also, could this be converted to NTSC?
The previous thread about the UM6561 says that you should just have to replace the 26.6MHz crystal with a 21.5MHz crystal and it automatically changes encoding and frame rate. Assuming it is one.


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PostPosted: Wed Sep 12, 2018 12:23 pm 
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Joined: Tue Feb 14, 2017 9:50 am
Posts: 89
I'll try to find a proper 5V supply but if the NoAC proves to be faulty, I might not even try to swap the crystal.


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