I'm really looking forward to working on the proper DIY carts once you get the boards going again! Thanks again for all your work documenting these boards the pinout has been extremely helpful in troubleshooting this cart.
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Since there are two address bits on the EPROM being toggled (19, 20), I think that should result in splitting the EPROM into 4x1MB addressable 'chunks' - perhaps the purpose of this is to load a BIOS or some kind of specific code region at startup, and then transition into regular program code later?ĭoes anyone know if this GAL has been dumped, and if so, where I could obtain a JED (or otherwise documentation on the logic) for it? Or alternatively, could I use a modified ROM or a different GAL program (perhaps one of the ones intended to do similar EPROM region remapping for Fluffy's boards) to reach a working state?Ĭlick to expand.Perfect, great to know I'm on the right track! I could be misinterpreting this, but it seems to me like the purpose of this GAL is to ingest the upper address lines that don't exist on the 27c322 (PA21-23) and map them to different regions of the EPROM. I've traced the pinout of the GAL and it seems to connect as follows: So it seems like the next logical thing to check is the GAL that interfaces with the Program ROM. Added a pullup resistor between pin J1 21 and +5V (per 's pinout document, although the board did not originally have anything here) Manually traced out all address lines from the Program ROM Desoldered ROM, dumped, verified against known working ROM data, tested replacing with known working 27c322s with several different ROM images including the one I dumped from and a known working dual boot ket/ketarr ROM Cleaned contacts on PGM motherboard socket and cartridge edge Traced power and ground, checked continuity Reflowed all relevant components on PROG board (Program ROM, both GALs, resistor arrays) I've done a bunch of diagnostic work on it: From this I've inferred that it's probably an issue with the Program ROM or its path to the motherboard. The motherboard is known working, including with other Lydz boots. No blind play, sound, or other indication that anything of substance is happening. The general problem is that the board does not seem to meaningfully boot I just get garbled graphics and intermittent video desync, almost as if it is 'boot looping' or resetting itself.
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Partly it's because I want to play the game, but mostly it's because I'm trying to familiarize myself with how the PGM stuff works and how to troubleshoot and repair it in preparation for putting together a set of 's PCBs when those start shipping again. I bought it from a friend knowing that it was broken, and I'm interested in it as a project, so I'm not keen to contact the seller or send it out - at least not yet I'd like to try repairs first myself. I have a broken Lydz Ketsui bootleg that I'm trying to get working again.
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