Snes APU01 revision with missing diode

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sidgallup
Posts: 14
Joined: Thu Mar 28, 2019 8:09 am

Snes APU01 revision with missing diode

Post by sidgallup »

Attached its a picture i found on the int3rn3tz of an Snes console APU 01 revision.

Ive had one of these for a few months in my backlog and it only shows a black screen, after inspecting it i noticed it is missing one component marked as D2 (SHVC) which i marked in RED, i have a few dead donor boards but none of the same APU01 revision, so my questions trying to fix this are...

1 ) Can i just take a diode from a donor board and put it into the area i marked with YELLOW, which is marked as D1 (SHVC) ? all my donor boards have this component also marked as D1 (SHVC) and they seem to fit on that spot

2 ) whats the name of te missing component so i can order a 1 to 1 replacement online from Mouser or Aliexpress?
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Super-Famicom-SNS-CPU-1-APU-01-board-front.jpg
Joe
Posts: 650
Joined: Mon Apr 01, 2013 11:17 pm

Re: Snes APU01 revision with missing diode

Post by Joe »

sidgallup wrote: Wed Mar 29, 2023 5:01 pmIve had one of these for a few months in my backlog and it only shows a black screen,
According to the schematics here, if that diode is missing, the SNES won't turn on at all. Are you sure there's a black screen?
sidgallup wrote: Wed Mar 29, 2023 5:01 pm1 ) Can i just take a diode from a donor board and put it into the area i marked with YELLOW, which is marked as D1 (SHVC) ?
If the problem is really a missing diode, try replacing it with a wire. That diode protects the SNES from a reversed power supply, so the SNES will work perfectly fine without it as long as you use the correct power supply.
sidgallup wrote: Wed Mar 29, 2023 5:01 pm2 ) whats the name of te missing component so i can order a 1 to 1 replacement online from Mouser or Aliexpress?
It's a Schottky diode. Any Schottky diode capable of handling roughly 1.5A and 25V should be fine. Here's one that can fit as D1. I don't know what size D2 should be, but I'm sure you can find one that will fit.
nitro2k01
Posts: 252
Joined: Sat Aug 28, 2010 9:01 am

Re: Snes APU01 revision with missing diode

Post by nitro2k01 »

It appears that D1 and D2 are connected in parallel and that they're just different options for the same component, depending on what they could buy the cheapest for a given production run. Unless D2 is faulty, no action should be required. You can check D2 in diode mode using a multimeter in diode mode. It should show about 0.5 V in the forward direction, and OL in the reverse direction.

Just to check the simple things, was the power button connected to the P3 connector when you were troubleshooting? You may have disconnected it when disassembling the SNES and never thought of it. No power button connected, no power coming through.

Another easy thing to check is the fuse (F1). Should show close to a short. Then check the voltage regulator for 5V when power is connected. With the basic power stuff sorted out, you can start looking at more advanced troubleshooting.
sidgallup
Posts: 14
Joined: Thu Mar 28, 2019 8:09 am

Re: Snes APU01 revision with missing diode

Post by sidgallup »

Joe wrote: Thu Mar 30, 2023 10:34 amif that diode is missing, the SNES won't turn on at all. Are you sure there's a black screen?
yes youre correct, i made a mistake, what i shouldve said is i get no power at all, not just black screen.
Joe wrote: Thu Mar 30, 2023 10:34 amIf the problem is really a missing diode, try replacing it with a wire.

Yes, i did that today, jump wire on D1 and now i read 5v on all main chips on the board, which means they are all getting power, however, now there is an actual black screen, tried to usual, cleaning the cart connector, checking the multiout for broken joints, didnt find any issue. So, theres deffinitely a dead chip on this board, it has no signs of corrosion so i have to start to troubleshoot by replacing 1 chip at a time.
This unit has a CPU Rev B, are these prone to dying? in my limited experience and by reading on the internet, CPUs that are dying like fies are the first revision, im not sure where to start but i have a few donor boards i can use to replace every chip, thinking about starting with the S-APU, then if CPUs REV B are prone to failing i will replace that one with a REV C i have.
nitro2k01 wrote: Sat Apr 01, 2023 4:53 am was the power button connected to the P3 connector when you were troubleshooting? No power button connected, no power coming through.

Another easy thing to check is the fuse (F1). Should show close to a short. Then check the voltage regulator for 5V when power is connected.
Hi yes the power switch was connected, and the fuse is good, i just did a jump wire on D1 and now i can read 5v through all the components on the board, so now i need to find the dead chip, ill start with the S-APU then the CPU.
sidgallup
Posts: 14
Joined: Thu Mar 28, 2019 8:09 am

Re: Snes APU01 revision with missing diode

Post by sidgallup »

Update... used a jump wire on D1 and now the console turns on, however it booted to a black screen everytime with every game i tried so i started by replacing the CPU with a Rev C i have from a donor board, still black screen, then i went for the SAPU chip which i got from a dead Snes Jr ive had for a long time that i could never fix, and finally this APU revision is booting and showing signs of life...

However, it only boots to the first screen with a few games by CAPCOM which have a splash screen with the copyright info before that classic CAPCOM jingle, in other words it is behaving like an original CPU 01 model when you remove the sound module, which means this SAPU chip i salvaged is damaged but at least boots unlike the original SAPU chip that just made the console stay on a black screen.

I think this is the end of the road since i dont have any other donor boards to get another working SAPU chip, maybe one day some will find a way to replace these SAPU chips with the chips that were used on older revisions, i have a few of those.
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