Cart PCB schematics?

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akokun
Posts: 16
Joined: Tue Apr 06, 2021 12:40 pm

Cart PCB schematics?

Post by akokun » Sun May 09, 2021 12:22 am

Wondering if there are available schematics for snes carts. I'm diagnosing an Actraiser cart which is on PCB SHVC-1A3B-11, which was the type used on several early SRAM games like FF2/4. Diode D1 showed continuity with no voltage drop across it, so I removed it, but it has a nice voltage drop of 0.6v on the multimeter diode test. Now, with the diode out the two points still show continuity, so actually there's continuity across a whole lot of stuff on this board across the backplane, and I'm not sure the cause of it, but it's probably why the game doesn't boot...

Edit: Noticed something else. I get continuity from the cathode via (with black probe) of D1 to the anode via (red probe), but I don't get any from the cathode via (red probe) of D1 to the anode via (black probe), and keep in mind the diode that's supposed to be here is completely desoldered and gone. My guess is there is some other semi-conduction issue going on somewhere else in the circuit but I have no idea where yet.

Edit2: FF4 cart also has the same continuity, so maybe that's normal for this PCB revision and I just don't understand how the cart works well enough. (Although, my FF4 ALSO doesn't boot)

Edit3: I don't know what the hell happened but I just soldered the diode back and plus all the reflowing I did earlier seemed to fix the game in general and now it works. I believe the diode circuit has something to do with saving to SRAM due to lack of the mad chip, I just don't understand it well enough to know what was going on.

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poorstudenthobbyist
Posts: 249
Joined: Fri Jun 24, 2016 4:20 pm

Re: Cart PCB schematics?

Post by poorstudenthobbyist » Sun May 09, 2021 8:11 am

I've got an explainer about the SNES cart (without the MAD chip) that might help, it should have the same SRAM control connections as your board

https://thepoorstudenthobbyist.com/2019 ... tion/#sram

(The section hyperlinks don't appear to be working so I need to go fix that, but scroll to the SRAM section)
Check out my website for NES, SNES, and Genesis tutorials here. And visit my store for some custom tools and boards for making games here.

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akokun
Posts: 16
Joined: Tue Apr 06, 2021 12:40 pm

Re: Cart PCB schematics?

Post by akokun » Sun May 09, 2021 8:21 pm

whoa thanks! that's way more than I had hoped to find.

Edit: I see now that that configuration is just an OR gate for powering the SRAM from either source so it makes sense the continuity I was getting...

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