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Ok as I was half expecting, I've been chasing a red herring. The PROMs work fine. Just to verify, I wrote the contents to an EEPROM I had lying around, and connected it to the same address pins as the one on the PCB. Testing all the output pins, I'm getting the exact same reads as on the PCB...

That's a pretty cool idea. I think I can make up something similar just using probe clips for the 5 address pins and the three data ones that I'm suspecting. Is it possible to piggyback a hack solution like that on to the suspected failing IC when the legs are constantly reading low, or would...

To me that adapter sounds like a band-aid solution moreso than a method to test for the source of the problem (the price, waiting for shipment, etc.). I'll keep it in mind though if it ends up becoming relevant. Hopefully someone has a good idea for anything else I could try testing on my PCB.

I was thinking that. It's a "N82S123AN". As far as I can tell "AM27S19PC" is a drop-in replacement, which I can source at a surmountable price, but I'm not sure how to write to one. I only have a TL866II, and if it's supported by its software I don't know what to identify it as. It's soldered...

All I could read from the mame source was that whoever wrote it had no idea an are just guessing. The BPROMs don't seem to actually do anything in MAME, even though they are a part of the rom set. I took a logic probe to both BPROMs, and a few data pins show no activity on each, as well as one...

I'm back to shamelessly leech on the knowledge of this forum with another PCB problem, hoping that someone around here knows enough about Toaplan hardware to recommend where to begin looking. This is my third Toaplan PCB with an issue (out of six) - what an unfortunate statistic ;( I've actually...

At the only electronics store that carry them locally. Nice theory ^^, but the cheapest I can realistically find is about $25 imported from Germany (providing 16V tolerant ones can fit where the 10v ones are supposed to go). That's still not too bad, and worth doing for sure. But I'd still like...

At least 8 of them are like $15 each. It's a simple operation but a big investment for something that might not be the cause. I'd like to at least hear some knowledge to back up a recap. Edit: found a German ebay seller with better prices, but would like to at least start out with the most...

I just replaced a really wonky 5v adjustment pot on my New Astro City power supply (400-5261Y), and though the new one is rock solid, it seems there's still an issue with it. Even with the pot turned down to 0ohm, I only read around 5.45v at the edge with no game connected. This is enough, or...

I should probably have mentioned that I already tried this (took a hint from the repair log I linked previously), and with the watchdog disabled the CPU stops resetting, but it will be stuck on the test grid pattern that appears slightly before the game "boots up". Here's a video someone...

This is exactly what I would be expecting. I'm a software guy, not a hardware guy, but I've worked with assembly code on a lot of old school hardware. So as long as it's relevant to the software, and address mapping etc. this is the kind of language that makes sense to me XD I was actually...

Yeah, there's nothing visible on the board. I'm suspecting there's a faulty IC somewhere on the board, and since the error doesn't happen until a certain place in the code, it would be one that's not used until that point... so I guess probably a RAM chip?

So for whatever it's worth I checked all the socketed EPROMs, and they match the MAME checksums. I also measured the voltage directly on the 68k CPU, and it's a fine 5v. I'm not sure I have the tools to figure out what's causing the resets, so if there are no known issues or other probable...

This is the kind of stuff I wanted to hear. :) Was it a Konami board also?

I tried just changing a couple of bytes on a MAME rom, and the check immediately failed, so I assumed it's a thorough checksum - but really it's just an assumption.

Either way, it's all running on the CPU, so if the ROM check runs as it's supposed (and even the EPROM reinitlializing works) I'm going to assume the CPU is doing fine. That would be my immediate assumption, but wouldn't that result in an error message during the ROM check though? As far as I...

Precisely No need to skip 101 stuff, I might easily overlook things. I didn't have the socketed chips out of the sockets, but I've pushing them all down properly. I figured if they weren't working well, they wouldn't pass the ROM check though. Doesn't that do a full checksum? I've also tried...

I have an issue with my Sunset Riders that has persisted since I got it. At the time I complained to the seller who assured me that the PCB was just super picky about the 5v supply. I didn't have a PSU with an adjustable 5v, so I just foolishly believed him (though it may have worked to him, so...

Haha man, that sounded all cool until I took a look at said IC, and it's this massive SMD chip with a billion tiny pins. I could splash a bunch of flux over it and carefully run my soldering iron over it, but I'd be deadly afraid of just making things worse. It's not a risk I'd be willing to...

I have a Truxton II that isn't working, and people keep suggesting that I replace the HK-1000 with the custom reproduction. But from what I can read here, the IC is mostly handling i/o stuff, so I'd assume that even if there's an issue with it on my board, it would at least still turn on...