First, the short version: Is there any manual/guide/tutorial/video explaining how to use the VHG1 vocal/guitar expansion card? The manual of the PA80 is very cryptic and I've been so far unable to make the card work.
Now, the long story

I've recently had the opportunity to get an used PA80 in very good condition and price, so I purchased it. Although I already own a PA5X and a Genos, I thought that I'd give it a good use for rehearsals and for playing with some colleagues at work. I used to have a Microarranger so I knew about the sound quality and capabilities. The PA80 seems to work flawlessly so far.
Just a few days after the purchase, I found a VHG1 expansion card, which (in theory) was "new old stock", so previously unused. I installed it following the instructions, and the PA80 seems to recognize it (the options and parameters of the vocal/guitar menu, which are only visible when the card is installed, are there). I'm not a guitarist and my intention was to use only the vocal harmonizer functions. The problem is that I haven't been able so far to make it work. No matter how I change the parameters, it's just as if the card wasn't there. Not a single harmony has come out from the kayboard. I've read the manual so many times, but it isn't helpful at all and I don't know what to do. I even do not know if I simply don't know how to use it or if the card itself is faulty. In fact, it seems that there isn't even a funtion to activate or deactivate the harmonizer, or at least I've been unable to find it.
It's not the first time that I use the harmonizer functions in a keyboard, as I already own a PA5X and a Genos, and in the past I had the now ancient, then great, Yamaha 9000 Pro. In Yamaha keyboards using the harmonizer is a breeze; in the PA5X is a bit more complex but I haven't had many problems. In the PA80 it's just impossible.
Any help would be much appreciated!