Jamma boards and +5V

[TuZhao]

Hi all,
I'm in the process of connecting my Raiden jamma board to a TV. Some months ago I played it succesfully for a few hours on my old Hantarex arcade monitor and Hantarex power supply, which powered both the monitor and the board.
Then I had to store away the board and all the jamma wirings because of lack of room, waiting for a better moment.
Eventually something in the monitor (which I continued to use with my DC and Saturn) broke (it was made in 1986: it fulfilled its duty, anyway!), and I had to trash it.
To cut the story short: now I play on a TV and I have resumed my jamma-on-tv project, I bought a Jamma power supply, plugged my Raiden board, rewired the video output to SCART standard (with the 5V and resistor to pin 16 for RGB mode), and nothing happens.

Assuming that the board is still functional (never touched it after the test I made months ago), and assuming that I might well have connected 1 or 2 wrong pins in the SCART plug, what scares me is that I should at least hear the demo sound from the speaker (like I did on the famous test), but I hear just a low humming sound, which raises when I raise the onboard volume trimmer (but that looks like normal background noise from a powered speaker).
I know for sure the demo sound option is on (double checked the dip switches).
I even connected the -5V line which it seems being used by a handful of games (on the Raiden service manual it clearly states to connect the -5V).

So here's my question: to what extent can the adjustable +5V power supply line influence jamma boards' ability to boot up? In other words, should I try to give Raiden an extra kick raising the +5V or I'll only do damage? At the moment I set it to 4.98V.

Any help appreciated!

[NeWmAn]

Have you wired pin 8 (AV mode select) on the SCART?
Can you wire a speaker to the JAMMA connector to hear if the sound is OK?
Regarding voltage: you should be able to go slightly over 5v (5.1 ~ 5.2v) without problems, most problematic boards require it.

[TuZhao]

Uh yeah the +5V was the problem! I had to push it up to 5.28 V, but now Raiden runs, as beautiful es ever
In the SCART socket I just connected the R, G, B, video ground (pin 18), fast blanking (pin 16), sync (pin 20). Nothing else! I watched closely the Saturn RGB cable as a guide.