Glad to have found this forum, where there are so many well-known retrogaming hardware experts around! Having some SNES software and hardware experience myself (translation, ASM, console & cart modding), this is the place I've been looking for.

Well, let's head on to business. I recently ventured building a 32 Mbit SNES cart using one 16 bit 27C322 EPROM. I used Siudym's untested schematics.
Here's what the completed thing looks like:

I know it's butt-ugly, but hey, it's my very first beta HiROM 27C322 SNES cartridge.

And unfortunately, it does not work. All I get is a black screen once that baby is powered up.
I tried to e-mail Siudym for a solution, but he didn't reply. Then I asked d4s for help - thanks again, dude! - but to no avail. Even with his suggestions, I wasn't able to get this thing to work.
Here's what I've tried so far:
- the original schematics (Siudym)
- connecting the SNES bus's A0 to pin 2 of the 139 and A1-A21 to A0-A20 of the EPROM respectively in order to avoid having to byte-swap the ROM in any way (d4s)
- not making the EPROM & SNES /OE connection (d4s)
- using HC microchips instead of LS ones to make sure the ROM data gets on to the SNES bus fast enough (d4s)
Nothing works. I even tested it on d4s' Ultra16, which has a memory viewer. The banks C0-FF (which should contain the ROM data since it is a HiROM game) remain empty, just like when no cartridge is inserted at all. Also, I checked the voltages on the 139, the two 245s and on the EPROM itself to make sure I didn't forget to make all the power connections. All VCC pins are at +5V as they should, and VSS is at GND.
Now, does perhaps someone of this forum have any idea what could be wrong? Any help would be greatly appreciated as I really want to finally get this project to work.

Thanks in advance!
orwannon
N.B.Please don't bother suggesting alternatives like using 27C801 EPROMs (I have successfully built carts using these), a copier (I indeed own one), or a Tototek flashcart (I'm going to buy one anyway). In this thread, let's just talk about connecting 16 bit EPROMs to the SNES bus. Savvy?
