Are you maybe talking about a V70 and not a V75? There is/was a known issue about some transmitters with very short (under 3 hours) battery life. You should contact our service center ("contact us" below)
Hey Eric, I'm currently in the market for some wireless systems, so I've been checking out the Line 6 systems. I took a V75 on demo, and was dismayed that I could only get about 1hr20 out of a set of batteries. So I broke out a new set, and no change, no more than an hour and a half!
I took it back to the shop, thinking it was faulty, and they said thay would have a look at it. A few weeks later, I went back and I took a new V75 to try. No different, around an hour!
So I went and bought myself a new pack of Energisers (really good quality batteries), and after using it for more than an hour, it was still showing 7h20 remaining.
So.... not sure exactly what was going on, but it seems that you need to use good quality batteries with this. The previous ones I was using were Panasonic, and we were using the 9V versions on our older Shure wireless units with good results.
Hope this helps.
I've spotted quite a few fake "Panasonic Gold" alkaline batteries on market stalls, here in Australia. I'm sure Matsushita's on to it, (as are their lawyers) just as I'm sure that any top quality alkaline AA's (including genuine Panasonics) give me around 8 hours in any of my seventeen XD-V transmitters.
I tend to favour the "bulk" ten or twenty supermarket blister-packs of "top-of-the-range" or "ultra" in either Duracell or Energiser, as those supermarkets (being sure to avoid counterfeits by using only reputable mainstream stores) seem to be able to retail them for less than the bulk price direct from Mallory or Eveready, ...given the relatively small quantities I need.
I've set this out in more detail, including my occasional load-and-forget use of lithium AA's, in this discussion: