eBay is all a bunch of jerks

Rant:

I bought a lot of "untested" neo geo 1 slot boards last year, and finally got around to screwing with them. Now, we all know that untested is code for broken, because how do you prove its untested? Well, let me tell you how. This pinwheel who sold these to me obviously tried to fix them, and is an even worse solderer than I am.

A resistor pack is missing from one board, both main power filtering capacitors are missing, and it's laughably obvious that he tried to desolder the upright cartridge riser on this one and just got sick of it and decided to unload them.

Well guess what, jokes on you buddy. I see how you screwed up a couple traces, trying to add a capacitor to "fix your startup issue", but desoldering the whole thing? Here's a pro tip: check the roms first, the bios was dead - you didn't need to go butcher at all. 15 minutes from someone with a clue and this one works fine.

I think if you sell something as "untested" it should at least imply that it hasn't obviously been screwed around with by an idiot.

End Rant, on to stuff:

First, Neo Geo news.. I got two of these boards working, and one left. I got so excited about Neo Geos that I bought a 6-slot board on eBay, to upgrade from the 2-slot in my cabinet. I got more Neo Geos than any one man could possibly need. I'll unload the single slots, I have no use for them. I don't know if I'll part with my 2-slot.

My PC10 project is on hold while I wait for some components. Everything works, and for the most part a NES cart coexists peacefully with regular games, but not all of them do. I'm going to try and scratch build an adapter, and mess with running certain lines through a switch, and using a solid state relay to power the cart when it's selected. It may never be perfect, NES games were never designed to be sharing a bus with other NES games. Maybe the only really right way would be a whole assload of buffer drivers, or 4066 switches.

I've also been playing with PCB designs for an adaptor I could have made. I still promise to post a pinout once I've figured out the last couple of issues, and if I get to the point I can have some made, I hope to be able to do it for about 50 bucks a unit, though thats more of a target than any sort of promise.

Some games will always look weird, the PC10s PPU handles some color codes a little differently, the emphasis bit, I beleive, the ones programmers weren't really supposed to use but did.

This also lead me to discover that some PC10 graphics have adjusted pallettes, because the intro screen to Mike Tyson Punch Out NES cart looks like a plate of diarreah on the PC10, but the PC10 game pak looks right. It's not a big deal, it's mostly noticable when mega man is a bright baby blue, instead of his usual mega-man blue. Most games look much better with a true RGB pallette.

As for decoding the instruction prom, I've made a little success... I think, I've ordered a couple serial eproms to test a theory.

I figured something out, though. The PC10 single board version I have, has the z80 side outputting inverted RGB natively, the NES outputs RGB natively, and it is inverted on board. The three pot's on board are for the inverter on the NES side, which looks like a typical inverting amplifier op-amp circuit. The signals are switched via 4066's, and I hope to see if I cant strap the z80 side to the inverter, the nes side to output natively, and thus have a RGB native PC10. I'd much rather not have the NES video signal mussed with thus.

I looked into/at the VS sytem a little more. There are two nes-like systems onboard, and it can output to two monitors simultaneosly. The two boards can share a RAM through an interrupt somehow, this feature was used by baseball and tennis, maybe others. Most single-game boards only have one side populated, but one could populate both, and rig a 4066 based board to switch whats on-screen.

My board had a hidden find, a 2A04 CPU is socketed on the empty side, the normal nes CPU being the 2A03. Someone probably switched game chips, and forgot to pull it.

This perhaps solves my Duck Hunt mystery, that is, why Duck Hunt eproms play with screwed up sound. The VS games used some different PPUs, with different color pallettes. This was partially the copy protection, and is well known. I had read the Duck Hunt sound issue as having to do with the custom PPU, but it never made sense. The PPU's don't make sound, the CPU does. I now know there were at least two CPUs used, and I'm guessing Duck Hunt uses this one. I have everything I need to thus test my Super Mario / Duck Hunt board as soon as I burn some eproms for it. I'll steal the PC10's PPU for the test, since it's the same pallette Duck Hunt used, and try it with the 2A04 I have. It'll be Duck Hunt and Super Mario Bros hooked to a pushbutton switch, and if I'm feeling froggy one day maybe I'll bankswitch some other games on there. Ice Climbers can share space with mario, and excitebike (I think) can live with Duck Hunt.

I fiddled with my Donkey Kong board, I put in a new Z80 and at least this one doesn't get hot to the touch, but still no joy. I dumped all the eproms and checked them, except for the two 2532s. I can't read those directly, but I should be able to repin a socket to a 2732, and at least be able to read it, though probably not write them. I should be getting something onscreen, even without them, though. There's a 74193 near the CPU on there that looks munged, it's a good candidate for replacement.

That reminds me, here's a tip for willem design eprom pcb owners: disable windows plug n play while dumping roms. It can poll for printers, and when it does it can set VPP (programming voltage), and you can actually be programming the devices you think your reading, and that could suck. It's also good practice IMO to run the hardware test, since it'll clear the ports, and make sure the VPP led isn't lit up. I don't think you can kill eproms this way, but I'm sure other things you could.