Broken snes, need part identification

[Pasky]

Just picked up a junk snes from somewhere here locally. I think I know what happened. For one the power fuse is bypassed with just a wire, and a component near the power regulator is burnt away, literally has a hole burnt through it.

It's labeled on the D1 of the snes motherboard, does anyone know what kind of component this is so I can find a replacement and see if this fixes the entire unit?

[whicker]

I believe D1 to be a SOT89 package. (measure it! It should be 4.5mm across horizontally as shown in your photo. if it's something else like 6.5mm, please tell me).

It is a schottky diode.
It needs to be rated for at least 1 Amp "average rectified output current". (1 amp continuous forward biased).
30V or more reverse biased should be enough... although I think the 100 in the part actually means 100V peak repetitive reverse voltage.

Forward voltage drop for this typical part is 0.8V, so pretty much anything nowadays can meet that (have even a lower forward voltage drop). It's not too important as the regulator burns up the excess voltage anyways.

As pictured (edited):
The middle pin on the bottom and the large pin on top are connected together. This is the Cathode.
The pin on the left is the Anode.
The pin on the right is nothing.

this is basically a single diode, but you might have trouble sourcing such a thing.
if you find a part that has either dual configuration, that will be alright (the diode on the right won't be used).

Code: Select all

          o
          |
o--->|----o----|<---o

or

          o
          |
o--->|----o---->|---o

[Pasky]

Thanks.

[Pasky]

Ok, I replaced the 7805 regulator with a new 7805 and the burnt diode with a 1n4001. The SNES still does not power on. I verified that it's not the power switch by using a known working one from another SNES. I'm getting 14v at the fuse block, 14v at the cathode on the replaced diode. But I'm only getting 0.2v on the anode and 0.2v on the input to the regulator. Is the 1n4001 I used a dud or maybe this is simply the wrong part to use?

http://imgur.com/kc8s14x,eNeOVx2,O4pB3xP,PnpEMXX#0

[lidnariq]

The only real advice I have at this point is: take the schematic I linked and follow components in—they're all labeled, so you should be able to find them, even if the traces disappear—and see which component no longer has the requisite voltage.

Edit: Upon further inspection, I'm getting 0.2v from the anode side of the diode and the regulator is getting 0.2v on it's input. Perhaps a 1n4001 will not work? Or do I have the cathode and anode reversed (pretty sure I don't)?

Sure sounds like you put it in backwards. And ... looking at my SNES and your picture, it sure looks like you put it in backwards.

Also, please put the fuse back in.

[Pasky]

Are you certain? Going by whicker's instructions I have it correctly. The cathode is on the left and the anode is bridging the 2 middle pins.

[lidnariq]

Look at it like this: How else are you going to get a diode blocking 13V? Either you've got it backwards, or there's a short afterwards that's destroying the diode because you've got no fuse. Either way, you'll need to unsolder the one you've got there.

[Pasky]

Reversed the diode and I got power back. Sweet. Thanks for all the help everyone.

[whicker]

hmm. I'll check the meter I used to see if it identifies diodes backwards (at this point in time these cheapo LCD meters can be wrong about most anything). If it does I'll update the post above.

Great to see another SNES back in service again

[blargg]

The anode goes to the positive from the adapter, the cathode to the regulator. Basically think of the stripe as the negative, since it's like a negative symbol.

[whicker]

The anode goes to the positive from the adapter, the cathode to the regulator. Basically think of the stripe as the negative, since it's like a negative symbol.

Yep exactly.
I screwed up when measuring it. The meter I have identifies the Anode with the red lead, after testing.