Is the S-APU in SNS-CPU-APU-01 and all 1-chip boards
I mostly repair the older SNES revisions with 2 PPUs, but sometimes I do get 1-chip and Mini consoles. But basically my repair knowledge about those is nothing much beyond “clean the cartridge slot with alcohol, look for broken traces and if it still doesn’t work, toss in the parts box”. Since they don’t have a CPU or PPU that’s prone to failure (to my knowledge, at least), it’s not like there’s much of anything I can replace on them.
Eventually I accumulated a small pile of 1-chip boards that all would freeze at the publisher splash screen. This is a common issue on all boards and is caused when the system fails to communicate with the sound hardware for whatever reason. You can easily cause this problem in SHVC consoles by simply removing the sound module. On other boards it’s usually due to broken traces somewhere.
When I find this issue on consoles without a removable cartridge slot and I can’t find broken traces anywhere else, I don’t waste my time and just toss them atop the heap. Among those boards are about a half dozen 1-chips, most of which I found inside housing that was full of roaches and had lots of liquid damage and broken traces. Though I had fixed all the broken traces I could find on the boards, they would all still hang on the publisher splash screen, so I made the assumption—which seemed reasonable at the time considering the condition in which I acquired them—that there were more broken traces that I simply hadn’t found, probably under the cartridge slot, and gave up on them.
Years ago when I first started repairing SNES consoles I had, in fact, tried replacing the DSP and S-SMP chips on some GPM consoles with this problem. Of course, it didn’t fix the problem and I later found the broken traces on them that were really causing the issue. Ever since then I’ve always assumed the audio chips are pretty much okay and don’t just die for no good reason like the CPU and PPUs.
But I was digging through my parts boards pile today and found those 1-chip boards I had tossed aside. Earlier in the day I had fixed a Mini when I removed the VRAM and found broken traces beneath. Inspired by that success I decided I should check underneath the APU on a few of them that had rust in that area to see if the traces that ran beneath it had breaks in them. So I removed the APU from a few boards and walked away while they cooled.
When I came back I looked for broken traces, didn’t find any, and then soldered the APUs back onto the boards. But just for the heck of it I decided I would replace the APU in one of them with an APU I had salvaged from a trashed board. To my great surprise the problem was solved when I tested the board.
The donor board on the right was totally beyond repair.
To be sure this wasn’t a fluke, I grabbed another board that would freeze at the splash screen and removed the APU from it. I then soldered in the APU from a console that had a totally unrelated video problem. Once again, the problem was totally fixed.
This is both good and bad news to me. The good part is that now I can fix an issue with the later SNES revisions that few people probably realize is so easily fixable. The bad news though is that it may mean all of our 1-chips are probably prone to the APU failing and may be ticking time bombs, just like the older revisions. Heck, maybe even the Mini could be prone to this.
I happened upon a cheap 1-Chip console that wouldn’t power on and I took a chance on it. Turned out to be a fuse, but now that it powers up, I am getting this issue. I don’t have a spare APU and this small an IC is beyond my soldering expertise anyway. Do you offer this repair as a service?
No, I’m sorry, but even if I did offer a repair service, I don’t have spares either. I think the chip is only found on 1-chips, SNS-CPU-APU boards, and the SNES Mini, so it’s not something you can buy on its own. Plus I’m no professional, so I don’t trust my skill enough to work on a console that belongs to someone else.
The same issue though could be caused by other problems, such as a broken trace somewhere between the APU and the cartridge slot or the APU and the CPU. Although I fixed a few consoles with this issue by replacing the APU, I also had some with the same problem that weren’t solved by replacing it, presumably due to broken traces or damaged components somewhere. So it’s a pain in the neck trying to repair this problem, since so many different things could cause it and it’s not always easy to spot broken traces visually. If there were schematics out there it’d maybe be a bit easier, but honestly, I’d probably just list the board on eBay with a description of the problem if I were you.
I run a CPU museum and would be interested in your non-working APU’s, as they are an interesting processor (SPC700 core at least).
As a side note, the single chip APU was used in some inflight entertainment systems on commercial jets as well. Made for a company called MAS.
Wow, I never knew something like that existed. Sounds very cool. It kind of reminds me of the Sega Mega Jet.
I just had a look around and I could only find one non-working APU. I’d be happy to send it to you though. I’ll ship it out tomorrow to the donation address.
The work you’re doing is so incredible. The amount of information in the Museum is just staggering. I love it!
Thank you very much, yah its an odd beast. Its a backplane based computer, a single card contains 2 or 3 complete SNES systems (CPU, PPU1/2, DSP/SMP or APU)
Hello!!! my problem I have a Snes that does not recognize the control number 1, I thought it would be the control but when connecting it to player number 2 if it works, I already use several controls and they only work on the second player … I do not know why it does not work on the First, I hope you can give me a solution, thanks!
Hi,
Sadly, this could be due to a bad CPU. I’ve definitely had a few consoles where the controls didn’t work due to a bad CPU.
To confirm you should first check the area around the connector for the controller port flex cable for any obvious damage like scratched traces or damaged components. If it all looks good then you can try temporarily swapping over a set of control ports from a working console. Or you can buy replacement controller ports on eBay for about $10 to $15 if you don’t have another SNES. If the controls still don’t work after swapping over the ports from a good console, then it’s probably a bad CPU.
I have this issue on a 2 chip PPU at the moment and using a Burn-In test cartridge (repro of the SNES repair cartridges service technicians would have used), so it appears to not be only with the 1 chip models.