Famiclone with broken triangle (?)

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MLX
Posts: 110
Joined: Tue Feb 14, 2017 9:50 am

Famiclone with broken triangle (?)

Post by MLX »

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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lidnariq
Posts: 11429
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Re: Famiclone with broken triangle (?)

Post by lidnariq »

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.
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.
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.
MLX
Posts: 110
Joined: Tue Feb 14, 2017 9:50 am

Re: Famiclone with broken triangle (?)

Post by MLX »

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.
Drag
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Re: Famiclone with broken triangle (?)

Post by Drag »

It sounds like writes to register $400B aren't making it to the APU. The way the triangle is acting in Gimmick is what hints towards this being the issue (the downward sweeps for the drums are wrapping around). $400B also contains the note length setting, so that would explain why the notes are all the wrong length too.
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