it could simply mean that your screen is installed upside down to put my 2 cents in. otherwise the polarity on the v or h coil (if it is a crt) could be reversed.
well, it was designed for the home/nostalgia market and not a commercial setting or collectors so they didn't put too much effort into the interface. for the customers it was aimed at, if it played it was fine.
no. when i looked at the manual last night i read that you use the player 2 joystick when in menu mode to adjust the volume.
i haven't actually played with this board much; since i received it i plugged it into a one-player JAMMA cabinet to make sure it booted and i could switch the games. i've had too darn many projects and need to get working on the multi-Taito so i can play some Zoo Keeper.
I can adjust my volume by using the player 1 and player 2 joysticks on the control panel.
I do not go into any menu system to do this. While on the main game select screen, hold player 1 forward and hold it there... push player 2 forward and you'll see a volume indication on the screen (iirc it's a "number"... 1,2,3-->).
It took awhile for me to figure it out because initially I had it in a cabinet that only had one joystick.