Oh I see. Dave Wellington's pictures on page one of this thread appear to show that it has JVS hookup as well as a Jamma edge, but I don't have one so cannot confirm this.
even if that topic wasn't active long time I would like to provide an update. That topic might be interesting for some of you guys.
I just bought a Knights of Valour 3 HD board and made some tests on supergun setup.
At the moemnt I don't own a HD cab therfore I will power the board external an connect to HDTV via DVI cable.
I used a normal ATX power supply (5V / 12V) and it worked well. So it seems there is no -5V needed out from the JVS connector.
Out from the conversions inside of this thread nobody was able to confirm that the board could be powered via JAMMA connector only (only buttons via JAMMA are confirmed so far)
Board works with 5V/12V only so from my perspective there is no reason why the Board couldn't work with Jamma supply only without the JVS connector.
Just waiting for some left parts to finish my supergun setupt (side project of restoring a blast city panel). I will give a try and share my results when tests could be done.