SNES PPU Problem

Discussion of hardware and software development for Super NES and Super Famicom.

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MottZilla
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Re: SNES PPU Problem

Post by MottZilla » Sat Jul 29, 2017 9:01 pm

AWJ wrote:A bad connection between the PPU and VRAM would affect BGs as well as sprites, and I don't see how a bad connection between PPU1 and PPU2 could affect just one out of every 8 pixels like that (the pixel bus between the two chips carries one pixel at a time) I would guess that one of the on-chip data lines to the line buffer on PPU1 has failed--not something that can be fixed short of replacing the chip with one from another SNES.
So one of the PPU chips probably had an internal failure? I do agree that the connection to VRAM is probably fine. I thought maybe it could be something communication related between PPU1 <> PPU2 but if it's as you say then I guess some internal chip function has failed. Are you fairly sure it's PPU1 that would have the failure? Or could it be PPU2? I guess I'll have to find someone to swap it out but being sure which of the two is defective would help.

creaothceann
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Re: SNES PPU Problem

Post by creaothceann » Sun Jul 30, 2017 1:54 am

Probably the one that is closest to the output, which would be PPU2 (5C78).
My current setup:
Super Famicom ("2/1/3" SNS-CPU-GPM-02) → SCART → OSSC → StarTech USB3HDCAP → AmaRecTV 3.10

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MottZilla
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Re: SNES PPU Problem

Post by MottZilla » Wed Aug 02, 2017 3:05 pm

Does anyone else have an opinion on which PPU is at fault? It'd be easier and cheaper to only have to replace 1 PPU chip and not both.

lidnariq
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Re: SNES PPU Problem

Post by lidnariq » Wed Aug 02, 2017 4:02 pm

It's going to be hard to find these as loose parts. (By which I mean, someone else is going to have to have opened a SFC/SNES and pulled the IC using good equipment in order to send it to you)

And it's a big enough surface-mount device that you'll really need a hot air rework station to remove the one on your mainboard anyway...

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MottZilla
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Re: SNES PPU Problem

Post by MottZilla » Wed Aug 02, 2017 7:09 pm

I don't plan on doing any of that myself. I don't have those tools or skills to do that. But should I decide to get it done it would help to be pretty confident in which chip is bad. For the time being I did the more sensible thing and just acquired another unit.

creaothceann
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Re: SNES PPU Problem

Post by creaothceann » Thu Aug 03, 2017 4:38 am

Hopefully an otherwise broken one, because hacking apart a good console would be bad :)
My current setup:
Super Famicom ("2/1/3" SNS-CPU-GPM-02) → SCART → OSSC → StarTech USB3HDCAP → AmaRecTV 3.10

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MottZilla
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Re: SNES PPU Problem

Post by MottZilla » Fri Aug 04, 2017 10:19 am

That's the idea. It wouldn't make sense to part out a fully functional console.

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