There does not seem to be a lot of information out there regarding the SEGA I/O I purchased, but it is indeed very nice and has full analog button support and adjustable 3.3v powered from the Jamma connector much like the Capcom I/O. Believe it was one of the last JVS I/O’s SEGA produced.
Details for it from the JVS service test page:
I’m running my NAOMI in 31khz to a VGA CRT Monitor, which I’ll also output my Dreamcast to when I get around to doing an internal VGA mod to it.
15khz mode via DIP switch, just simply does not work directly outputting from the NAOMI itself. I just get a black screen with occasional “squiggles” of coloured lines. I suspect the sync line is out of spec and internally the NAOMI may still be outputting 480p?
If I take the 15Khz output from the Jamma connector after being processed by the SEGA I/O it appears to give out an interlaced 480i image, which is somewhat blurry. The bending/warping of the image at the very top of the screen is only occurring on my 14" PVM. I’m not sure why as it has no issues with anything else.
Nothing to worry about though as even the service manuals state the 15khz signal is likely to be inferior:
I think the Capcom I/O does a better job of processing the NAOMI’s 15khz than SEGA’s from what scant information I have gathered.
Yesterday I opened up my NAOMI and replaced the CR2032 battery which was really at the end of its life already:
I also spent the time cleaning out the dirt from the CPU fan heat-sink using compressed air…
…and replacing the case fan which was really noisy. I had purchased a fan cheaply when Maplins were closing down as a spare for my CPS2 in the future, which is the identical sized replacement so I used that!
Look at all this built up grime:
The connectors and wiring were different so I de-soldered the wires and switched them over.
But first I had to file back the plastic a bit on the Maplin fan to gain easier access to the soldering pads:
I then placed the fans sticker I had to remove earlier back in it’s original placement to help prevent dirt being blown into the fans bearings while in use:
My NAOMI is now a lot quieter and with a better airflow rate!
I do need to purchase a super capacitor and replace it sometime. But it does contain and hold a charge now and is not leaking so no rush quite yet, which means savings are now setting persistantly as well!